T Cells Stop to Smell the (Antigenic) Roses Pamela J. Fink J Immunol 2006; 177:1379-1380; ; This information is current as doi: 10.4049/jimmunol.177.3.1379 of October 1, 2021. http://www.jimmunol.org/content/177/3/1379

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The Journal of Immunology is published twice each month by The American Association of Immunologists, Inc., 1451 Rockville Pike, Suite 650, Rockville, MD 20852 Copyright © 2006 by The American Association of Immunologists All rights reserved. Print ISSN: 0022-1767 Online ISSN: 1550-6606. T Cells Stop to Smell the (Antigenic) Roses Pamela J. Fink1

In 1971, prehistory for many contemporary read- Ab-forming cells, using a modification of a viral plaque-form- ers of The Journal of Immunology, MHC restriction ing assay. In this assay, spleen cells are seeded over a lawn of was yet to be outlined, TCR structure was unex- SRBC or HRBC in agar on a microscope slide and scanned plored, and T cell maturation remained shrouded some time later after the addition of complement for holes (or in mystery. However, elegant work in currently unfashionable plaques) in the lawn. Holes formed in the presence of antiglob- species such as sheep and rats had clearly established that lym- ulin Abs are called indirect plaques, and result from red cell cy- phocytes recirculate, traveling from the blood via lymph nodes tolysis upon secretion of SRBC- or HRBC-specific IgM or IgG to the lymph, and returning to the blood by way of the thoracic Abs by an Ab-forming cell, usually visible in the center of the duct (1, 2). All recirculating lymphocytes eventually traverse the plaque. Cytolysis in the absence of cross-linking antiglobulin Downloaded from thoracic duct. There were also data to suggest that lymphocyte (direct plaques) requires secretion of pentameric IgM Ab. This trafficking was altered by Ag exposure, and the notion that Ag- simple method allows quantification of Ag-specific IgM- and specific lymphocytes could be transiently recruited from the re- IgG-secreting cells. circulating pool was being bandied about (3). It was within this The crystal clear data of Sprent et al. (4) showed that thoracic setting that Jon Sprent joined Graham Mitchell in the lab of duct lymphocytes were depleted of SRBC-specific T cells dur-

Jacques Miller at the Walter and Eliza Hall Institute in Mel- http://www.jimmunol.org/ bourne and decided it was time to investigate lymphocyte re- ing the first 1 to 2 days of Ag exposure (whereas HRBC-specific circulation in the frustratingly small but inexpensive and genet- T cells were as abundant as they were before SRBC injection). ically malleable species of laboratory mice (4). Conversely, the thoracic duct lymph was specifically enriched Sprent learned to cannulate the minute thoracic duct of anes- for SRBC-reactive T cells by day 5 of Ag encounter. Upon Ag thetized mice, a daunting surgical feat that involved jeweller’s injection, the tissues of the primary donor animal efficiently fil- forceps, 0.5-mm bore nylon tubing, tissue adhesive, a fine horse tered Ag-reactive T cells, first depleting and then enriching their hair to remove lymph clots, and a steady hand coupled with numbers within the pool of recirculating lymphocytes. Sprent infinite patience. In these pre-animal-care-committee days, cannu- and Mitchell showed this process of “biological filtration” ap- lated mice were left for days to run on the top of a hamster wheel, plies equally to alloreactive lymphocytes withdrawn from recir- by guest on October 1, 2021 where they churned out around 20 ml of lymph daily (5, 6). culation 1 to 2 days after injection of histoincompatible lym- To determine whether Ag-specific T cells are recruited from phocytes. Thus, 2 days after injection of (CBA x C57BL/6)F1 the circulation by Ag exposure, Sprent and Mitchell injected spleen cells, thoracic duct lymphocytes from CBA mice were CBA mice i.v. with SRBC and collected thoracic duct lympho- unable to cause graft-vs-host response (measured as splenomeg- cytes over the course of the next 5 days. Why use sheep eryth- aly) when transferred to (CBA x C57BL/6)F1 neonates, but rocytes? Sprent, Miller, and Mitchell reasoned that using a mul- their ability to respond to (CBA x BALB/c)F1 mice remained ticomponent Ag would be more likely to yield a generic answer, unabated (4). rather than one that applied only to that particular antigenic From this foundation, only minor technical embellishments response. SRBC also offer an easy means of enumerating Ab- a b were required to negatively select (MHC xMHC )F1 T cells in forming B cells to measure the extent of T cell–B cell collabo- a Ag-injected parental MHC hosts and show that Ag-specific F1 ration. The abundance of sheep in Australia probably figured T cells able to collaborate with MHCb B cells remained. These into this choice too. To assay for Ag-induced alterations in lym- experiments, performed in 1978, revealed that (MHCa ϫ phocyte trafficking, Sprent and Mitchell assessed the presence MHCb)F T cells are comprised of largely nonoverlapping sets of specific T cells in a secondary host, an adult thymectomized, 1 of Ag-specific T cells able to help MHCa and MHCb B cells (7). irradiated, bone marrow reconstituted mouse (4). This T cell- This strongly implied that each T cell expresses a single type of depleted secondary host provided a ready supply of naive B cells. T cells were supplied by an inoculation of thoracic duct TCR, whether comprised of a single receptor or dual receptors lymphocytes from the original SRBC-injected donor, and their separately recognizing MHC and Ag. Additional experiments, in which MHCa T cells were negatively selected for MHCb ability to provide help for host B cells was assayed upon injec- b tion of either SRBC or horse erythrocytes (HRBC)2 as a con- alloreactivity by filtration through an MHC host, exposed no b trol. T cell help was quantified 6 days later by the number of or few residual Ag-specific MHC -restricted T cells (8). Such acute negative selection contrasted with the developmental tol-

erance induced in parent-into-F1 radiation bone marrow chi- 1 Address correspondence and reprint requests to Dr. Pamela J. Fink, Department of b a b Immunology, University of Washington, I-607H HSC, Campus Box 357650, Seattle, meras (MHC bone marrow reconstituted (MHC xMHC )F1 b WA 98195. E-mail address: pfi[email protected] mice), which revealed that MHC T cells developing in an a 2 Abbreviation used in this paper: HRBC, horse RBC. MHC -expressing environment could be restricted to recognizing

Copyright © 2006 by The American Association of Immunologists, Inc. 0022-1767/06/$02.00 1380 PILLARS OF IMMUNOLOGY

Ag on MHCa APCs (9). Acute negative selection and develop- Sprent’s experimental approach, largely restricted to in vivo mental tolerance had their vocal opponents and proponents in protocols, a result, Sprent claims, of his inability to use a tissue the 1970s, but we now accept that both techniques expose culture hood while smoking his pipe. His legacy of elegant in underlying properties of T cell development and Ag recogni- vivo experiments, such as those described in this “Pillars of Im- tion. Parent-into-F1 bone marrow chimeras revealed that both munology” article, may be one of the unexpected benefits of tolerance and MHC restriction specificity are developmentally pipe smoking. acquired (as we know now, in the thymus through positive and negative selection). Negative selection by filtration exposed References some inherent crossreactivity of MHC restriction specificity by 1. Gowans, J. L., and E. L. Knight. 1964. The route of re-circulation of lymphocyes in depleting alloreactive cells. the rat. Proc. Roy. Soc. B. 159: 257–282. 2. Hall, J. G., and B. Morris. 1965. The origin of the cells in the efferent lymph from a Our knowledge of the mechanisms by which T cells recircu- single lymph node. J. Exp. Med. 121: 901–910. late has also greatly expanded since 1971. We now understand 3. Ford, W. L., and R. C. Atkins. 1971. Specific unresponsiveness of recirculating lym- that T cells carried through the blood into the spleen can enter phocytes after exposure to histocompatibility antigen in F1 hybrid rats. Nat. New Biol. 234: 178–180. the white pulp and exit via the marginal sinuses. Alternatively, 4. Sprent, J., J. F. A. P. Miller, and G. F. Mitchell. 1971. Antigen-induced selective T cells can pull themselves from the blood into the lymph nodes recruitment of circulating lymphocytes. Cell Immunol. 2: 171–181. 5. Boak, J. L., and M. F. A. Woodruff. 1965. A modified technique for collecting mouse by means of a carefully controlled multistep process of adher- thoracic duct lymph. Nature 205: 396–397. ence to and extravasation through high endothelial venules, 6. Miller, J. F. A. P., and G. F. Mitchell. 1968. Cell to cell interaction in the immune coupled with chemokine-regulated microenvironmental hom- response I. Hemolysin-forming cells in neonatally thymectomized mice reconstituted

with thymus or thoracic duct lymphocytes. J. Exp. Med. 128: 801–820. Downloaded from ing and exit through the efferent lymph (10). Recent advances 7. Sprent, J. 1978. Two subgroups of T helper cells in F1 hybrid mice revealed by neg- in intravital microscopy have allowed visualization of traffick- ative selection to heterologous erythrocytes in vivo. J. Immunol. 121: 1691–1695. ing T cells in live mice (11). 8. Sprent, J., and H. von Boehmer. 1976. Helper function of T cells depleted of alloan- tigen-reactive lymphocytes by filtration through irradiated F1 hybrid recipients. I. The discovery of biological filtration clearly provided the Failure to collaborate with allogeneic B cells in a secondary response to sheep eryth- foundation for our understanding of lymphocyte homing and rocytes measured in vivo. J. Exp. Med. 144: 616–626. 9. Sprent, J. 1978. Role of H-2 gene products in the function of T helper cells from the basis for experiments detailing the MHC restriction of T normal and chimeric mice in vivo. Immunol. Rev. 42: 108–137. http://www.jimmunol.org/ cell function. It also served as the foundation for the prolific 10. Campbell, D. J., C. H. Kim, and E. C. Butcher. 2003. Chemokines in the systemic organization of immunity. Immunol. Rev. 195: 58–71. scientific career of Jon Sprent, being one of the first of more 11. Halin, C., M. J. Rodrigo, C. Sumen, and U. H. von Andrian. 2005. In vivo imaging than 260 articles he has published to date. The work is typical of of lymphocyte trafficking. Ann. Rev. Cell Dev. Biol. 21: 581–603. by guest on October 1, 2021