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Mechanism of B Cell Tolerance Establishing Anergy As a Bona Fide Establishing Anergy as a Bona Fide In Vivo Mechanism of B Cell Tolerance Andrew Getahun, Shannon K. O'Neill and John C. Cambier This information is current as J Immunol 2009; 183:5439-5441; ; of October 2, 2021. doi: 10.4049/jimmunol.0990088 http://www.jimmunol.org/content/183/9/5439 References This article cites 21 articles, 9 of which you can access for free at: Downloaded from http://www.jimmunol.org/content/183/9/5439.full#ref-list-1 Why The JI? Submit online. • Rapid Reviews! 30 days* from submission to initial decision http://www.jimmunol.org/ • No Triage! Every submission reviewed by practicing scientists • Fast Publication! 4 weeks from acceptance to publication *average Subscription Information about subscribing to The Journal of Immunology is online at: by guest on October 2, 2021 http://jimmunol.org/subscription Permissions Submit copyright permission requests at: http://www.aai.org/About/Publications/JI/copyright.html Email Alerts Receive free email-alerts when new articles cite this article. Sign up at: http://jimmunol.org/alerts 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 © 2009 by The American Association of Immunologists, Inc. All rights reserved. Print ISSN: 0022-1767 Online ISSN: 1550-6606. Pillars of Immunology Establishing Anergy as a Bona Fide In Vivo Mechanism of B Cell Tolerance Andrew Getahun, Shannon K. O’Neill, and John C. Cambier1 he pioneering work of Owen (1) and Burnet and Fen- However, these experiments did not discriminate whether ner (2) in the late 1940s originated the concept of this was due to clonal deletion or to the induction of a state T immune tolerance. Subsequent experiments con- in which the cell persisted but was simply unresponsive to ducted by Billingham et al. (3) first demonstrated the active Ag. To address this question, Pike and Nossal used a fluo- induction of immune tolerance using a skin graft rejection rescein (Flu2)-human gamma globulin (HGG) tolerization model. These authors consequently coined the phrase “ac- protocol in conjunction with analysis of both the capacity to tively acquired immunological tolerance.” The findings of produce Ab responses and enumeration of the Flu-specific B Billingham et al. were put into structural perspective by cells (13). They found that in mice treated neonatally or in Downloaded from David Talmage’s hypothesis of cell selection (4) and Bur- utero with high doses of Flu-HGG, there was a significant net’s clonal selection theory (5), both published in 1957, reduction in the number of Flu-binding cells, suggesting which provided a framework for understanding how it might clonal abortion/deletion. However, when they used low Ag be possible to maintain tolerance to self while remaining re- doses they found no reduction in the number of Flu-binding sponsive to foreign Ags. Specifically, if one B cell encoded a cells or their avidity profiles; nevertheless, the cells did not single specificity, deletion of self-reactive cells would provide produce Abs upon stimulation. They coined the term clonal http://www.jimmunol.org/ tolerance while sparing responses to other Ags. An important “anergy” to describe this B cell unresponsiveness. qualification of the clonal selection theory was proposed by Although the conclusions of Pike and Nossal would be Joshua Lederberg (6), who postulated that lymphocytes tra- proven correct, there were some caveats in their experimental verse a developmental stage during which they are uniquely approach. For example, their reported Ab-forming cell pre- sensitive to tolerance induction. Of course we now recognize cursor frequency was much lower than would have been that this principle applies to so-called “central tolerance,” predicted based on the Ag-binding cell frequency. Therefore wherein autoreactive cells are silenced by deletion (T and B) the differentiated daughters of Ag-binding cells remaining and receptor editing (B) that occur in the bone marrow and after tolerance induction may never have been capable of by guest on October 2, 2021 thymus. Gradually, additional silencing mechanisms were producing measurable anti-Flu responses, e.g., prior to tol- defined, such as those involving suppressor/regulatory T erance induction. Moreover, like all previous B cell tolerance cells, idiotypic regulatory networks, and anergy. Silencing of studies, the approach involved tolerization with exogenous autoreactive B cells by anergy was first established unequiv- foreign Ag in contrast to the physiological situation in which ocally by the Pillars of Immunology article (7) that is the sub- the self-Ag would be present throughout the ontogeny of au- ject of this commentary. toreactive B cells. Finally, the tolerogen used in the studies, Among the earliest indications that B cells per se could be Flu-HGG, would bind the inhibitory IgG constant receptor rendered tolerant were the experiments of Siskind and col- Fc␥RIIB expressed by the B cells, and this could suppress the leagues in 1963 (8) in which pneumococcal polysaccharides subsequent immune response. Thus, although Pike and were used as tolerogens/Ags. The “thymus independence” of Nossal originated the concept of anergy, Chris Goodnow responses to this Ag made it unlikely that T cells were in- and his mentor Anthony Basten (7) proved that anergy is volved in silencing the response. Subsequent in vitro studies operative in the silencing of autoreactive B cells in vivo. using isolated B cells clearly demonstrated that these cells As reported in the featured publication, Goodnow and could be rendered tolerant (9–12). Consistent with the hy- Basten et al. (7) took advantage of the then newly developed pothesis of Lederberg, these studies also showed that imma- transgenesis technology to express hen egg lysozyme (HEL) ture B cells were more sensitive to tolerance induction than as a neo-autoantigen in mice. The Ag was expressed under a mature B cells, requiring 1000-fold less Ag than mature metallothionein promoter to facilitate expression from em- splenic B cells to achieve tolerance (9). bryonic to adult life. Furthermore, use of this promoter al- In early studies, the mechanism by which B cells were lowed the modulation of Ag expression by exposure to heavy tolerized was often referred to as clonal inactivation/abor- metals. In these mice (ML5 line), the expression of HEL in- tion. It was shown that the frequency of Ag-specific, Ab-pro- duced tolerance in both HEL-specific B and T cell popula- ducing cells fell drastically following tolerization treatments. tions, confirming that it was recognized as self. ML5 mice 2 Abbreviations used in this paper: Flu, fluorescein; HEL, hen egg lysozyme; HGG, human gammaglobulin. 1 Address correspondence and reprint requests to Dr. John C. Cambier, 1400 Jackson Street, K803, Denver, CO 80206. E-mail address: [email protected] Copyright © 2009 by The American Association of Immunologists, Inc. 0022-1767/09/$2.00 www.jimmunol.org/cgi/doi/10.4049/jimmunol.0990088 5440 PILLARS OF IMMUNOLOGY were then crossed with a B cell Ag receptor transgenic line volves some durable form of reprogramming or is reversible. (MD3) that expressed a BCR with a high affinity for HEL. The transfer of anergic B cells into an environment lacking The IgM and IgD of the MD3 mice were of the Igha allotype HEL gradually (over days) results in loss of the anergic phe- that, when on an Ighb background, allowed tracking of the notype and reacquisition of the ability to produce Ab re- MD3 B cells and production of IgMa by these cells or their sponses to HEL (18). Complementary studies using the daughters. lower affinity Ars/A1 model indicated that the anergic phe- The results of the experiment were striking. The presence notype is lost within minutes of the dissociation of autoan- of HEL did not lead to the deletion of most MD3 B cells; in tigen (19). Although the delay in the loss of anergy upon the fact, they were present in the periphery in nearly normal transfer of MD3 ϫ ML5 B cells could be interpreted as re- numbers but exhibited reduced surface IgM levels. Interest- sulting from a requirement for the decay of a transcription- ingly, IgD expression remained high. Although MD3 mice ally regulated repressor, other data suggests this might be due had high spontaneous IgMa anti-HEL titers, MD3 ϫ ML5 to the relatively high affinity of the MD3 antibody for HEL ϭ ϫ 9 Ϫ1 double transgenic mice produced barely detectable levels of (Ka 2 10 M ) and thus slow dissociation of HEL from IgMa anti-HEL Ab. Moreover, in an adoptive transfer exper- Ag receptors. Taken together, these data are most consistent iment in which either MD3 or MD3 ϫ ML5 spleen cells with a requirement for the constant transduction of a BCR were transferred into sublethally irradiated C57BL/6 mice signal to maintain anergy (19). ϫ together with HRBC-primed T cells, HRBC-HEL immuni- The MD3 ML5 system established anergy as a mechanism of B cell tolerance. However, the model is unphysiologic in its zation led to drastically lower anti-HEL responses in recipi- Downloaded from ents of MD3 ϫ ML5 spleen cells than in recipients of MD3 reliance on transgenes and an Ag receptor possessing extremely spleen cells. high autoantigen affinity. Thus the studies did not establish ab- These results grounded the clonal anergy theory. A year solutely the contribution of this mechanism to physiologic B later, David Nemazee and his colleagues would demonstrate cell tolerance in the wild-type repertoire. Goodnow did com- pare the phenotype of the B cells in MD3 ϫ ML5 mice with clonal deletion of autoreactive B cells in a BCR transgenic those in wild-type C57BL/6 mice and concluded that a popu- model specific for MHC class I (14).
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