sign in sign up
<<
Home , Forebrain, Hypothalamus, Medial forebrain bundle, Preoptic area, Septal area, Stria terminalis

Molecular Psychiatry (1998) 3, 397–404  1998 Stockton Press All rights reserved 1359–4184/98 $12.00

ORIGINAL RESEARCH ARTICLE Circumscribed lesion of the medial bundle area causes structural impairment of lymphoid organs and severe depression of immune function in rats KI Pasternak1,2, C Timo-Iaria2, CJ Rodrigues2, DA Maria2, AJS Duarte2, L Paiva2, DH Pozzi2,BBde Mendonça2, M-L Wong1 and J Licinio1

1Clinical Branch, Intramural Research program, National Institute of Mental Health, NIH, Bethesda, MD 20892-1284, USA; 2Faculdade de Medicina da Universidade de Sa˜o Paulo, 01246-903 Sa˜o Paulo, SP, Brazil

Interactions between the immune system and the are a key element in the pathophysiol- ogy of diseases such as multiple sclerosis, neuroAIDS, and Alzheimer’s, which affect large numbers of individuals and are associated with a high social cost. However, the neuroanatom- ical basis of brain-immune interactions has not been elucidated. We report that in Wistar rats of either sex bilateral electrolytic lesion of the reduces body weight by 28% 7 days after lesioning, and causes widespread infections, , adypsia, structural damage to the lymphoid organs and heavy depression of T lymphocytes cytotoxicity. The following alterations occur in the immune system after those lesions: the weight of the thy- mus, spleen and lymphonodes is reduced by 77.9%, 49.1% and 48.4%, respectively. The thy- mus is atrophied and contains fewer lymphoid cells in the cortex than in the medulla. In the spleen the white pulp is reduced and lymphoid cells from periarteriolar zones and at the chords are almost absent. In lymph nodes cortical small lymphocytes are depleted and pri- mary and secondary nodules and germinal centers all but disappear. Cytotoxicity of lympho- cytes is reduced by 86.2% in the thymus, 77.6% in the spleen and 70.2% in lymph nodes. The critical area of lesion is at the medialmost portion of the medial forebrain bundle, at the preop- tic area and rostral part of the anterior . We suggest that this area contains neural circuits that are crucial for keeping the structure of lymphoid organs and the functional integrity of the immune system. Keywords: lymphoid organs; cytotoxicity; medial forebrain bundle; hypothalamus; thymus; spleen

Introduction et al,19 who observed that electrolytic lesions of indi- vidual nuclei in the mouse medial hypothalamus The regulation of immune function is accomplished by depresses lymphocyte cytotoxic activity, whereas a variety of complex mechanisms involving , cell-to-cell communication, , and neural cir- lesions of all the nuclei cause only a slight reduction cuits. Peripheral immune mechanisms have been in lymphocyte cytotoxic activity. These data indicate investigated to a great extent but the neural structures that there may be a functional interaction between that play a role in such regulation have not been fully hypothalamic nuclei that produce a balance between identified.1 Brain immune interactions have an activation and deactivation of immune function. important role in the pathophysiology of diseases such To investigate the anatomical basis of neuroimmune as multiple sclerosis, neuroAIDS, and Alzheimer’s, interactions, we conducted hypothalamic lesions to which are highly prevalent and have a profound social determine whether lesions of specific areas of the cost.2–9 hypothalamus affect the functioning of the peripheral Several studies have demonstrated that the central immune system. We designed the experiments participates in the regulation of described below in order to accomplish the following: immune function.10–21 Immune deficiency may result (1) to determine the critical hypothalamic area associa- from lesioning the hypothalamus and the reticular for- ted with the immune depression that followed lesion- mation,22–24 the medial septal nucleus25 and ing; (2) to ascertain the effects of those lesions on the basalis of Meynert.26 A complex pattern of neural regu- size and structure of lymphoid organs and on lympho- lation of the immune system was found by Belluardo cyte toxicity; and (3) to verify whether changes in the structure and function of lymphoid organs were sec- ondary to deprivation or to changes in corticos- Correspondence: Dr K Pasternak, Rua Austria 141, Sa˜o Paulo, SP terone levels. 01447, Brazil Received 2 February 1998; revised 6 April 1998; accepted 24 April 1998 Hypothalamic lesions and lymphoid organs KI Pasternak et al 398 Materials and methods Hepes (Riedel de Haen AG D-3016 Seelze 1, Germany), l Adult Wistar rats of either sex, weighing 160–200 g, 1% -glutamine, and 5% inactivated bovine fetal underwent electrolytic lesion of the lateral portion of serum at pH 7.4 was used to sensitize the animals. In preoptic and anterior hypothalamic areas. Animals the control group a sterilized saline solution was were anesthetized with ketamine hydrochloride injected intravenously. Thymus, spleen and lymph 50 mg kg−1 plus flunitrazepan 10 mg kg−1 (intraperito- nodes were removed for the lymphocyte cytotoxicity neally injected) and fixed to a stereotaxic instrument test. The lymphoid organs were cut into pieces, washed for bilateral, symmetric lesions with 1 mA current dur- and placed in a Petri dish containing 199 medium ing 5 s by means of a stainless steel semimicroelectrode added with 2 nM Hepes, 4 nM NaHCO3 (Mallinkrodt, −5 (50 ␮m in diameter at the tip). The electrode was pos- USA) and 5.10 M 2 mercaptoethanol and thereafter itioned according to the atlas of Koening and Klippel,27 passed through nylon wool columns (nylon fiber 38.1 29 initially aiming at lesioning from A:5.2 to 7.0, L:1.2 to mm type 200) for separation of adhering cells. One 2.0, and H:2.0 to 3.0. The critical lesion was circum- hour after incubation the material was centrifuged scribed to a tiny strip within the medial portion of the (1800 rpm) at room temperature for 10 min. Sub- medial forebrain bundle at the and a sequently, non-adherent cells, T-lymphocytes, were small strip of the anterior hypothalamus. resuspended in 199 medium supplemented with 2 nM × −5 When the lesioning procedure was completed, the Hepes, 4 nM NaHCO3 and 5 10 M mercaptoethanol 29 animals received penicillin and were thereafter kept in and used as effector cells. individual cages. Because lesions caused complete aphagia, rats were intragastrically fed three times a day Corticosterone levels with a standard laboratory diet food suspended in milk Corticosterone was measured by radioimmunoassay (50% liquid, 50% solid mix). Control and sham-oper- (RIA). In deeply anesthetized animals, was col- ated rats were also fed the same way. All animals were lected by cardiac puncture in heparin 40 min after the weighed daily. When infection occurred a combination anesthetic had been injected, to reduce to a mini- of penicillin and streptomycin was used. mum. Anticorticosterone antibodies (from Radioassay Within 7–10 days of surgery, animals developed Systems Laboratories) and a tritiated (3H) antigen were infection. Therefore, for our experimental purposes, used in the RIA. rats were killed 6 days after lesioning. During autopsy we searched for signs of infection or inflammation. Thymus, spleen and inguinal lymph nodes were Histology removed and their fresh weights were determined, and of the lesioned and sham-lesioned animals were they were preserved for histologic examination. Brains also removed for Nissl-staining to assess the lesioned were removed and processed for the identification of areas in the L group and electrode position in S. Sec- the extent and topography of lesions in 10-␮m, Nissl- tions of the lymphoid organs were stained with hema- stained sections. The adrenal glands were also toxylin-eosine for histological examination. removed and weighed. In the control group lesions were made in the par- Lymphocyte mediated cytotoxicity (LMC) ietal cortex. In the sham-operated rats the semimicro- T cells were incubated in 96 wells in round-bottomed electrode was introduced in the brain but no current microtiter plates with ×10551Cr-labeled SRBC,30 was passed; the electrode was positioned one milli- resulting in an E/T ratio of 50:1 in a total volume of meter above the critical area, because the target area 0.2 ml RPMI/FCS. Each culture was performed in trip- was very small and its tunneling by the electrode could licate. The plates were incubated for 18 h at 37°C. The produce an effective lesion, which we had found to cultures were then centrifuged for 1 min and 50 ␮lof occur in preliminary experiments. An additional con- the supernatant from each well were removed and the trol group consisted of animals deprived of food and 51Cr release was measured in a gamma counter. Spon- water for 6 days. taneous release of 51Cr was determined from target cells Corticosterone levels were measured to determine if alone and maximum release was obtained by the changes in immune function were associated with addition of distilled water to the 51Cr-SRBC. Cytotoxic- alterations in the levels of this stress-responsive hor- ity was calculated as the relative (percentual) specific mone. lysis (cpm of the test group as related to cpm of spon- Immune function tests taneous release), according to the following for- 31–34 Five groups were used to assess lymphocyte cytotoxi- mula: city function: normal (N), control lesion (C), sham specific lysis = lesion (S), medial forebrain bundle area lesion (L) and a control group, consisting of non-lesioned animals that experimental cpm − spontaneous cpm × 100. were fasted for 7 days (F). Three days before being maximum cpm − spontaneous cpm killed, the animals were intravenously injected with sheep red blood cells (SRBC) and treated according to the technique described by Miller et al.28 A 2.108 SRBC The percentage of maximum cpm relative to spon- suspension in 199 medium supplemented with 2 nM taneous cpm was over 90% in control experiments. Hypothalamic lesions and lymphoid organs KI Pasternak et al 399 weight loss in the infected group (28.0%). When lesions were restricted to the medial strip, some ani- mals were able to eat and a little but loss of weight was similar to that of the animals with complete lesion of the medial forebrain bundle. A slight loss of body weight also occurred in control (C) and in sham-operated (S) rats, as compared to nor- mals (N) (Table 1), probably due to the surgical pro- cedures. There was no significant difference between the weight of the C and S groups but both were differ- ent (P Ͻ 0.01) from the lesioned (L) group.

Lymphoid organs Thymus, spleen and lymph nodes’ weights were compared among the three experimental groups, including L animals in which infection was prevented. Table 2 shows that in L rats thymus weight Figure 1 A rat subjected to lesion of the medial forebrain was sharply reduced (by 77.9%) as compared to the bundle (below) is compared to a normal rat (above). Both had normal group (P Ͻ 0.001); in L, thymus weight was also a similar weight at the beginning of the experimental period. significantly lower than in C and S groups (P Ͻ 0.01). Notice the piloerection and cachectic aspect of the lesioned Among C and S animals thymus weight was similar animal. but it was lower than in N (P Ͻ 0.01); weight loss was, respectively, 20.3% and 21.2% lower in C and S than Statistical analysis in N. The significance of differences between groups was Spleen weight was only affected in L rats, in which assessed using analysis of variance (ANOVA) followed there was a weight loss of 49.1% in relation to group by post hoc correction (Duncan test). Statistical sig- N(P Ͻ 0.01 in comparison to N, C and S). Lymph node nificance was assumed for P Ͻ 0.05. weight was equally reduced (48.4% as related to N) in the rats with a lesion in the medial forebrain bundle area. Results The role of infection in weight loss was assessed by Body weight comparing the effects of lesioning of the medial fore- The animals in which the entire medial forebrain area brain bundle area among animals that were treated was bilaterally lesioned (which included the critical with antibiotics and those that were not. As shown in area) soon exhibited the lateral hypothalamic syn- Table 3, infection was not the cause of weight loss, drome. They adopted a curled posture, walked little because its prevention did not change the proportion and slowly and became apathetic, reacting weakly and of either body or lymphoid organs’ weight reduction only to strong sensory stimuli. Most animals did not after lesioning. eat or drink spontaneously. Loss of weight evolved rap- Lymphoid organs were structurally affected in the idly towards within 5 or 6 days (Figure 1), medial forebrain bundle lesioned animals but not in when weight had dropped on the average from the other groups. Thymus was clearly atrophied, yel- 194.42 ± 2.66 g (mean ± SEM) before operation to lowish and hardened. The vascular connective 139.93 ± 2.61 g (Table 1), which amounts to a reduction surrounding the lobules increased, subdividing the of 28% (P Ͻ 0.01). Loss of body weight could have into many small lobules which communicated been a consequence of infection but when the latter with medullary vessels. Figure 2 illustrates the deep was prevented by antibiotics, no significant difference structural changes undergone by the thymus in L ani- was found in weight between the groups with and mals as compared to normals. Demarcation between without infection. In non-infected rats the relative loss cortex and medulla in each lobule was poor and, con- of weight was 28.1%, therefore not different from the trary to what is normally found, medulla was more

Table 1 Body weight (in grams, mean ± SEM) just before (Wb) the experimental period began and when the animals were sacrificed (Ws)

NLCS

Wb 194.53 ± 3.44 194.42 ± 2.66 204.61 ± 3.53 218.19 ± 5.39 (n = 13) (n = 31) (n = 31) (n = 21) Ws 194.55 ± 3.41 139.93 ± 2.61a 197.81 ± 3.49 211.95 ± 5.80 (n = 13) (n = 31) (n = 31) (n = 21) aSignificantly different (P Ͻ 0.01) from Wb N (normal group) and from Ws L (lesioned), C (control) and S (sham-operated) rats. n = number of animals. Hypothalamic lesions and lymphoid organs KI Pasternak et al 400 Table 2 Organ weight (in grams ± SEM) at the day of sacrifice

Organ Group

NLCS

Spleen 0.914 ± 0.077 0.466 ± 0.023a 0.864 ± 0.032 0.911 ± 0.054 (n = 19) (n = 40) (n = 39) (n = 27) Thymus 0.217 ± 0.008 0.048 ± 0.001a 0.173 ± 0.008 0.171 ± 0.010 (n = 19) (n = 40) (n = 39) (n = 27) Lymph 0.031 ± 0.001 0.016 ± 0.001a 0.034 ± 0.001 0.032 ± 0.001 nodes (n = 19) (n = 40) (n = 39) (n = 27) Adrenal 0.038 ± 0.001 0.043 ± 0.001 0.041 ± 0.001 0.034 ± 0.001a glands (n = 13) (n = 31) (n = 31) (n = 21)

Spleen, thymus and lymph nodes; asignificantly different (P Ͻ 0.01) from N, C and S. Adrenal glands: asignificantly different (P Ͻ 0.01) from N, L and C.

Table 3 Body and organ weights (in grams, mean ± SEM) of rats with and without infection after lesioning

Infected Non-infected (n = 16) (n = 22)

Initial weight 202.37 ± 6.84 195.90 ± 3.33 (body) Final weight 143.50 ± 4.58 140.81 ± 3.09 (body) Spleen 0.512 ± 0.051 0.472 ± 0.035 Thymus 0.042 ± 0.002 0.047 ± 0.002 Lymph nodes 0.018 ± 0.001 0.015 ± 0.008 Adrenal glands 0.041 ± 0.002 0.043 ± 0.001

deeply stained than cortex. The latter was drastically reduced and small lymphoid cells depleted, being occupied by large cells with abundant and clear cyto- plasm; a few polymorphonuclear cells and mastocytes were located in scattered sites within the outermost layer adjacent to connective tissue. Medulla showed relatively more lymphoid cells than the cortex, thus generating the inverted overall picture of the gland. In some lesioned rats the thymus presented a striking structural disruption. The spleen gross structure was fairly preserved but reduction of the white pulp was patent. Lymphoid cells from periarteriolar zones and the cords all but dis- appeared (Figure 3). Lymph nodes from L rats were depleted from small lymphocytes in the cortical area (Figure 4). Primary and secondary nodules disappeared and the germinal centers were almost absent. A moderate increase of Figure 2 Microscopic structure of the thymus of a medial plasma cells was seen in the medullary cords. A thin forebrain bundle lesioned rat (a) as compared to a normal rim of secondary cortex was observed in several organ (b). In (b), a normal Hassal body; the characteristic con- lymph nodes. spicuous lobules with a pale medullary core surrounded by densely packed lymphocytes can be seen. In (a), there appears weight a corticomedullary inversion, due to the intense cortical lym- × The weight of the adrenal gland was not affected in phocyte rarefaction. HE, 170. any of the experimental groups, except for the sham- operated rats, in which there was a 10.5% reduction in comparison to the normal group (P Ͻ 0.01). Corticos- Hypothalamic lesions and lymphoid organs KI Pasternak et al 401

Figure 3 Microscopic structure of the spleen from a medial forebrain bundle lesioned (a) and from a normal animal (b). Figure 4 Microscopic structure of a lymph node from a Notice in (b) the well-developed Malpighian bodies and in medial forebrain bundle lesioned rat (a) and from a normal (a) the scarceness of lymphocytes that in (b) surrounds the animal (b). The dense cortical follicules, patent in (b), are central arteriole. HE, × 170 in (a) and × 80 in (b). absent in )a). HE, × 120. terone levels at the end of the experiments were stat- Table 4 Corticosterone levels at the day of sacrifice (in ␮g istically similar (P Ͼ 0.05) among all the experimental per 100 ml of plasma, mean ± SEM) groups (Table 4). NLCS Cytotoxicity Table 5 summarizes data obtained from the cytotoxic- 45.58 ± 7.79 51.90 ± 5.66 45.00 ± 5.24 45.45 ± 6.42 ity tests. Thymus lymphocyte cytotoxicity (expressed (n = 13) (n = 23) (n = 27) (n = 11) as mean ± SEM of the percentage of 51Cr released by the experimental vs control groups) was reduced by the critical lesion to only 13.8% of the normal value (P Ͻ 0.01), falling from 31.0 ± 3.6 in normal rats to toxicity increased significantly (P Ͻ 0.05) in the thy- 4.4 ± 1.2 in the L group. Among C and S rats no differ- mus (49.8 ± 11.5) and spleen (P Ͻ 0.05, 47.5 ± 6.4) but ence was found and neither group differed from nor- was not affected in lymph nodes. mals. Spleen lymphocyte cytotoxicity fell to 22.4% of the normal value, decaying from 30.4 ± 3.8 in N rats Topography of the lesion down to 6.8 ± 2.2 in the lesioned rats (P Ͻ 0.01). Impairment of lymphoid organs’ structure and function Lymph node lymphocyte cytotoxicity was reduced in as described above occurred following destruction of a the L group to 29.8% as compared to N rats, falling thin strip of the medial forebrain bundle area at the from 27.6 ± 3.8 to 8.2 ± 2.5 (P Ͻ 0.01). Among control preoptic and anteriormost hypothalamic regions. and sham-operated rats lymph node lymphocyte cyto- Figure 5a illustrates the site of the large lesion, at the toxicity was similar and did not differ from the N level of the preoptic region, and Figure 5b shows a group. small lesion confined to a thin portion of the medial In the animals starved for 7 days lymphocyte cyto- border of the medial forebrain bundle area. Immune Hypothalamic lesions and lymphoid organs KI Pasternak et al 402 Table 5 Cytotoxicity (in % of 51Cr released by the sample in comparison to release by the control, mean ± SEM) of lymphocytes from lymphoid organs in the four experimental groups

Organ Group

NLCS

Thymus 31.0 ± 3.6 4.4 ± 1.2a 26.1 ± 3.3 24.2 ± 3.0 (n = 10) (n = 12) (n = 10) (n = 8) Spleen 30.4 ± 3.8 6.8 ± 2.2a 30.5 ± 5.5 32.0 ± 3.4 (n = 10) (n = 12) (n = 10) (n = 8) Lymph 27.6 ± 3.8 8.2 ± 2.5a 35.7 ± 4.5 24.3 ± 3.1 nodes (n = 10) (n = 12) (n = 10) (n = 8)

aSignificantly different (P Ͻ 0.01) from N, C and S.

depression occurred only when the lesions were bilat- medialmost part of this brain region, ability of the ani- eral. mals to eat and drink was partially recovered but the alterations in immune function were not. Rostrally located lesions in the anteroposterior regions caused Discussion alterations in immune function; those lesions also Bilateral electrolytic lesion of a thin strip of the medial caused aphagia and adypsia. There is evidence that in forebrain bundle area at the preoptic and anteriormost the rat this region lodges glucoreceptors sensitive to hypothalamic regions caused body weight loss, thy- cytoglucopenia, whose lesion may impair mus, spleen and lymph nodes hypotrophy and and might therefore induce abnormalities reduction of lymphocyte cytotoxic activity. The litera- in feeding behavior.38 Morgane39,40 reported aphagia, ture on the effects of brain lesions on the immune sys- that did not evolve to spontaneous feeding, after pro- tem in general has been reviewed in detail by Cross.35 longed instrumental feeding and inexorable death in In our studies, we observed reduction of body weight rats subjected to localized lesion of the far-lateral by about one third in 1 week, despite intragastric feed- region of the , just medial to the ing and hydration, which maintained the animals ; however, no changes in immune adequately fed and hydrated. When lesion of the function were reported in those studies. medial forebrain bundle was completed at the preoptic All animals were adequately fed and hydrated and anterior hypothalamic levels, the animals could throughout the study; therefore, it is unlikely that not eat or drink at all but when only its medialmost either starvation or dehydration induced alterations in portion was destroyed they occasionally ate and drank. immune function in our experiments. We also docu- Depression of cytotoxic T cells activity, although more mented that complete food and water deprivation of pronounced when the entire medial forebrain bundle normal rats for 6 days caused a weight loss that was area was destroyed, was severe in either case. Recovery parallel to but was less prominent than that which from the failure to eat provoked by lateral hypothal- occurred in the lesioned rats; nevertheless, it did not amic lesions was first reported by Teitelbaum and Stel- provoke changes in the structure or function of lymph- lar.36 They observed that the crucial lesion that induces oid organs. aphagia and adypsia in the rat is located 1 mm above The severe impairment of structure and function of the floor of the brain and 2 mm off the midline on each the lymphoid organs that we observed in this study is side, extending all along parallel to the ventromedial evidence of interruption of a normal mechanism that nuclei. Left to eat spontaneously all the animals died directly maintains their trophism. Thymus involution within a few weeks but no catastrophic infections have has been previously reported after central lesion41 but been ever described in studies of the so-called lateral the type and intensity of the structural changes we hypothalamic syndrome. If properly fed, rats bearing found in this organ revealed a highly disrupting effect lesions in that region will start by themselves in of the lesion. The alterations in spleen and lymph about 10 days, mainly if offered food with a high fat nodes we detected, however, are similar to those content, and all the animals do eventually resume eat- reported by Isakovic and Jankovic.41 The hypothalamic ing of ordinary food and water.37 However, in prelimi- area they lesioned was more medially located as com- nary experiments in which the entire medial forebrain pared to our critical lesion. bundle area had been destroyed, we found that all rats Acute thymus involution has been found to occur died within less than 15 days after lesioning. under increased endogenous secretion or adminis- In our experiments, recovery of eating and drinking tration of androgenic, estrogenic and adrenocortical after whole medial forebrain bundle lesion at the pre- hormones, stress and starvation.42 The deeper optic and anterior hypothalamic levels never occurred, impairment of thymus in our study, in comparison to presumably due to the early death of the experimental spleen and lymph nodes, is expressed by its structural animals; when the lesions were restricted to the loss, which appears as an almost complete destruction Hypothalamic lesions and lymphoid organs KI Pasternak et al 403 Spleen and lymph node weight was reduced in L rats by approximately the same amount (near 50%) in com- parison to normal rats, which is much less than weight reduction of the thymus (86.2% as related to normal animals). The medial forebrain bundle is not a single fiber tract but a mesh of autochthonous , that entertain complex connections among themselves and with dis- tant neurons, and long projection fibers that course in both ascending and descending directions.43 The local neurons originate and/or mediate many behavioral and homeostatic functions (such as feeding and sexual behavior, , alertness, blood glucose regulation), requiring the activation of several distributed systems. This pattern of organization probably contributes to the impairment of immune regulation by the lesioning of several structures that are connected with the medial forebrain bundle (, , frontal cortex, nucleus of Meynert). In fact, the medial fore- brain bundle is a central link in an intricate network, which involves these structures and other, hypothal- amic and preoptic connections, related to the control of secretion of the pituitary hormones. Several pituitary hormones and endogenous do either inhibit (adrenocorticotropic , ␣-endorphin, leu- and met-enkephalin) or enhance (thyrotropic and ) immune function. The medial forebrain bundle could potentially influence the immune system through its connections with the preoptic and hypo- thalamic nuclei involved in pituitary function, parti- cularly hormones regulating hypothalamic-pituitary- adrenal (HPA) axis function.44,45 However, corticos- terone levels were not abnormal in our study. Further studies are needed to ascertain the mechanisms by which the medialmost portion of the medial forebrain bundle at the preoptic and rostral anterior hypothal- amic areas contribute to regulate immune function. In conclusion, our experiments suggest the exist- Figure 5 Schematic representation of the lesions which pro- ence, in the medialmost portion of the medial forebrain voked immune depression in rats. (a) A larger lesion, bundle at the preoptic and rostral anterior hypothal- embodying almost entirely the medial forebrain bundle area amic areas, of neural circuits that are essential for the at the preoptic level (in black). This lesion includes portions maintenance of the structure and function of lymph- of the medial forebrain bundle about 0.3 mm rostral and cau- oid organs. dal to this level (not shown). (b) A smaller lesion at the medialmost portion of the medial forebrain bundle area (in black), mostly at the suprachiasmatic level, around 0.3 mm Acknowledgements wide and deep and slightly less than 1.0 mm along the verti- cal axis. Abbreviations: ac, ; amy, amyg- The authors are indebted to Miss Neusi O Rolim for dala; c, cingulum; cc, ; cg, cingulate gyrus; technical assistance and to Dr Jacyr Pasternak for his cp, caudate-; f, ; gp, globuls pallidus; Ipo, lat- valuable suggestions. This research has been supported eral preoptic nucleus; mfb, medial forebrain bundle; mpo, by Fundaça˜o Faculdade de Medicina, LIM-HC-FMUSP, medial preoptic nucleus; oc, optic ; pm, magnocellular FAPESP and CNPq. M-L Wong is the recipient of a preoptic nucleus; sf, fimbrial spetalnucleus; sl, lateral septal Young Investigator Award from NARSAD. nucleus; st, interstitial nucleus of . References of the cortex, and weight reduction to only about one 1 Jankovic BD. Neuroimmunomodulation: facts and dilemmas. fifth of that prevailing in the normal organ. Thymus Immunol Lett 1989; 21: 101–118. lymphocyte cytotoxicity was reduced to 13.8% of the 2 Cacabelos R, Alvarez XA, Fernandez-Novoa L et al. Brain interleu- normal value. Whether atrophy of the organ and kin-1 beta in Alzheimer’s disease and vascular dementia. Meth Find Exp Clin Pharmacol 1994; 16: 141–151. reduction of cytotoxicity in thymus T lymphocytes are 3 Pachter JS. Inflammatory mechanisms in Alzheimer disease: the independent variables or the latter depends upon the role of beta-amyloid/glial interactions. Mol Psychiatry 1997; 2: former remains an open question. 91–95. Hypothalamic lesions and lymphoid organs KI Pasternak et al 404 4 Vitkovic L, da Cunha A, Tyor WR. expression and patho- 23 Jankovic BD. Structural correlates of immune microenvironment. genesis in AIDS brain. Res Publ Assoc Res Nerv Ment Dis 1994; 72: In: Jankovic BD, Jankovic K (eds). Microenvironmental Aspects of 203–222. Immunity. Plenum Press: New York, 1971, pp 1–4. 5 Chiang CS, Powell HC, Gold LH, Samimi A, Campbell IL. 24 Jankovic BD, Isakovic K. Neuro-endocrine correlates of immune Macrophage/microglial-mediated primary demyelination and response. I. Effects of brain lesions on antibody production, Arthus motor disease induced by the production of reactivity and delayed hypersensitivity in the rat. Arch Allergy -3 in transgenic mice. J Clin Invest 1996; 97: 1512–1524. 1973; 45: 360–372. 6 Issazadeh S, Lorentzen JC, Mustafa MI, Hojeberg B, Mussener A, 25 Labeur M, Nahmod VE, Finkielman S, Arzt E. Lesions of the septal Olsson T. Cytokines in relapsing experimental autoimmune ence- nucleus produce a long-lasting inhibition of T. lymphocyte pro- phalomyelitis in DA rats: persistent mRNA expression of proin- liferation. Neurosci Lett 1991; 125: 129–132. flammatory cytokines and absent expression of interleukin-10 and 26 Radosevic-Stasic B, Cuk M, Mrakovcic-Sutic Z et al. Immunological transforming growth factor-beta. J Neuroimmunol 1996; 69: 103– consequences of lesions of in rats. Int J Neurosci 115. 1990; 60: 325–327. 7 Michelson D, Stone L, Galliven E et al. Multiple sclerosis is asso- 27 Koenig JFR, Klippel RA. The Rat Brain. A Stereotaxic Atlas of the ciated with alterations in hypothalamic-pituitary-adrenal axis Forebrain and Lower Parts of the Brain Stem. Williams & Wilkins: function. J Clin Endocrinol Metabol 1994; 79: 848–853. Baltimore, 1963. 8 Sippy BD, Hofman FM, Wallach D, Hinton DR. Increased 28 Miller TE, MacKanes GB, Lagrange L. immunopotentiation with expression of -alpha receptors in the brains BCG. II. Modulation of the response to sheep blood cells. J Natl of patients with AIDS. J Acquir Immune Defic Syndr Hum Retrovi- Cancer Inst 1973; 51: 1669–1676. rol 1995; 10: 511–521. 29 Hudson L, Hay FC. Practical Immunology. Third edn. Blackwell: 9 Rudick RA, Ransohoff RM, Peppler R, VanderBrug MS, Lehmann Oxford, 1989. P, Alam J. Interferon beta induces interleukin-10 expression: rel- 30 Kay HD, Bonnard GD, West WH, Herberman RB. A functional com- evance to multiple sclerosis. Ann Neurol 1996; 40: 618–627. parison of Fc-receptor-bearing lymphocytes active in natu- 10 Ader R, Cohen N. CNS-immune system interactions. Conditioning ral cytotoxicity and antibody-dependent cellular cytotoxicity. J phenomena. Behav Brain Sci 1985; 8: 379–394. Immunol 1977; 118: 2058–2066. 11 Barne´oud P, Neveu PJ, Vitiello S, Morme`de P, Le Moal M. Brain 31 Herberman RB, Holden HT. Natural-cell mediated immunity. Adv immunomodulation in rats. Brain Res 1988; 474: 394– Cancer Res 1978; 27: 305–377. 398. 32 Herberman RB, Reynolds CW, Ortaldo JR. Mechanism of cytotoxic- 12 Felten DL, Felten SY, Carlson SL, Olschowska JA, Livnat S. Norad- ity by natural killer. Annu Rev Immunol 1986; 4: 651–680. renergic and peptidergic innervation of lymphoid tissue. J Immunol 33 Cerottini JC. Lymphoid cells as effectors of immunologic cytolysis. 1985; 135: 755–765. Hosp Pract 1977; 12: 57–68. 13 Williams JM, Peterson RG, Shea PA, Schmedtje JF, Bauer DC, 34 Calder EA, Penhale WJ, Barnes EW, Irvine WJ. Cytotoxic lympho- 51 Felten DL. Sympathetic innervation of murine thymus and spleen: cytes in Hashimoto thyroiditi. An ‘in vivo’ assay system using Cr- evidence for a functional link between the nervous and immune labeled red blood cells coated with thyroglobulin. Clin Exp systems. Brain Res Bull 1981; 6: 83–94. Immunol 1973; 14: 19–27. 35 Cross RJ. Hypothalamic-immune interactions: modulation of 14 Felten DL, Ackerman KD, Wiegand SJ, Felten SY. fibers immune function by electrolytic and chemical lesions in the central associate with lymphocytes and macrophages in specific compart- nervous system. In: Frier S (ed). The Neuroendocrine Immune Net- ments of the splenic white pulp. J Neurosci Res 1987; 18: 28–36. work. CRC Press: Boca Raton, Florida, 1990. 15 Felten SY, Olschowska J. Noradrenergic sympathetic innervation 36 Teitelbaum P, Stellar E. Recovery from the failure to eat produced of the spleen. II. Tyrosine hydroxylase (TH)-positive nerve ter- by hypothalamic lesions. Science 1954; 120: 894–895. minals form synapticlike contacts on lymphocytes in the splenic 37 Teitelbaum P, Epstein AN. The lateral hypothalamic syndrome: white pulp. J Neurosci Res 1987; 18: 37–48. recovery of feeding and drinking after lateral hypothalamic lesions. 16 Felten SY, Bellinger DL, Collier TJ, Coleman PD, Felten DL. Psychol Rev 1962; 69: 74–90. Decreased sympathetic innervation of spleen in aged Fischer 344 38 Timo-Iaria C. Glucoreceptor systems: from control of glycemia to rats. Neurobiol Aging 1987; 8: 159–165. feeding behavior. News Physiol Sci 1990; 5: 46–49. 17 Felten DL, Felten SY, Bellinger DL et al. Noradrenergic sympath- 39 Morgane PJ. Medial forebrain bundle and ‘feeding centers’ of the etic neural interaction with the immune system: structure and hypothalamus. J Comp Neurol 1962; 117: 21–25. function. Immun Rev 1987; 100: 225–260. 40 Morgane PJ. Alterations in feeding and drinking behavior of rats 18 Carlson SL, Felten DL. Involvement of hypothalamic and limbic with lesions of globi pallidi. Am J Physiol 1961; 201: 420–428. structures in neural-immune communication. In: Goetzl EJ, Spector 41 Isakovic K, Jankovic BD. Neuro-endocrine correlates of immune NH (eds). Neuroimmune Networks: Physiology and Diseases. Allan response. II. Chanes in the lymphatic organs of brain-lesioned rats. R Liss: New York, 1989, pp 219–226. Arch Allergy 1973; 45: 373–384. 19 Belluardo N, Mudo´ G, Cella S, Santoni A, Forni G, Bindoni M. 42 Dougherty TF. Effects of hormones on lymphatic tissue. Physiol Hypothalamic control of certain aspects of natural immunity in the Rev 1952; 32: 379–401. mouse. Immunology 1987; 62: 321–327. 43 Millhouse OE. A Golgi study of the descending medial forebrain 20 Neveu PJ. Minireview: cerebral neocortex modulation of immune bundle. Brain Res 1969; 15: 341–363. functions. Life Sci 1988 42: 1917–1923. 44 Sternberg EM, Chrousos GP, Wilder RL, Gold PW. The stress 21 Roszman TL, Brooks WH. Neural modulation of immune function. response and the regulation of inflammatory disease. Ann Intern J Neuroimmunol 1985; 10: 59–69. Med 1992; 117: 854–866. 22 Tyrey L, Nalbandov AC. Influence of anterior hypothalamic lesions 45 Sternberg EM, Licinio J. Overview of neuroimmune stress interac- on circulating antibody titers in the rat. Am J Physiol 1992; 222: tions. Implications for susceptibility to inflammatory disease. Ann 179–185. N Y Acad Sci 1995; 771: 364–371.