SummaryB cell knockout mice p, MT/p, MT were used to examine the requirement for B cell antigen (Ag) presentation in the establishment of CD4 + T cell tolerance. CD4 + T cells from p, MT mice injected with exogenous protein Ag in adjuvant responded to in vitro challenge by transcription of cytokine mKNA, cytokine secretion, and proliferation. Peripheral tolerance could be established in p~MT mice with a single dose of deaggragated protein. This tolerance was manifested by a loss of T cell proliferation and cytokine production (including both T helper cell type 1 [Thl]-and Th2-related cytokines), indicating that B cells are not required for the induction of peripheral T cell tolerance and suggesting that the dual zone tolerance theory is not applicable to all protein Ags and is not mediated through Ag presentation by B cells.T he role of B cells in Ag presentation to peripheral CD4 + T cell responses is controversial. Although B cells are the most abundant MHC class II-positive cell and have been shown in some studies to be involved in the activation of peripheral T cells, other investigators have argued against the notion that B cells are necessary as APCs for induction of T cell responses. Thus, results from studies have ranged from, first, the B cell as the crucial initiating APC in the lymph node (1), through second, the B cell as a necessary mediator of T cell clonal expansion and secondary proliferation (2-5), to third, normal priming and proliferation of T cells in the absence of B cells (6, 7). These studies all examined Ag-specific T cell activation in mice that had been rendered deficient in B cells, either by continuous injection of anti-p, Ab, by reconstitution of SCID mice with naive T cells, or, most recently, by targeted deletion of either the IgM heavy chain gene (8) or the JH gene segment (5, 9). The role of B cells in the induction of peripheral T cell tolerance is less controversial. B cells can serve as APCs in the induction of Ag-specific tolerance in naive CD4 + and CD8 + T cells (10, 11) and in Ag-specific T cell clones (12). These reports led to speculation by investigators that tolerance induction in virgin T cells is a primary function of the B cell.To reevaluate the role of B cells as APCs for activation and tolerization ofCD4 + T cells, we used the B cell knockout mouse ~MT/p~MT (hereafter p~MT), which was generated by introduction of a nonsense mutation into the transmembrane exon of the IgM heavy chain gene, resulting in a total deletion of B cells (13). The Ag used to investigate CD4 + T cell responses in these mice was human ~/-globulin (HGG), 1 which is a T-dependent Ag able to induce either tolerance or activation ofT cells, depending on the injection procedure. HGG injected subcutaneously in adjuvant induces T cell proliferation and cytokine secretion as well as a significant anti-HGG Ag response, whereas a single injection of deaggregated HGG (DHGG) induces a long-lasting peripheral tolerance that affects both B cells and T cells (reviewed in 14 and 15). In the case ofT cells, ...

SummaryThe induction of tolerance in mice to preparations of deaggregated human gamma globulin (DHGG) results in in vitro antigen-specific unresponsiveness in CD4 + T cells as well as in both the T helper 1 (Thl) and Th2-1ike subpopulations. Whereas both CD45RB hi and CD45RB l~ cells from lymph nodes of HGG/complete Freund's adjuvant-immunized mice (control) proliferated in vitro to HGG, both subpopulations from mice previously tolerized with DHGG failed to respond. Furthermore, CD4 + T cells from control, but not from DHGG-injected mice, secreted high levels of interleukin 2 (IL-2) after in vitro stimulation with HGG. Although significant levels of IL-4 in supernatants of control CD4 + cells stimulated with HGG were detected in some, but not all, experiments, significant levels of IL-4 were never detected in supernatants of HGGstimulated tolerant CD4 + cells. The demonstration that serum IgG1 anti-HGG is preferentially produced in a few tolerant mice that exhibit a leaky tolerant state suggests that tolerance induction may be more dif~cult to induce in IL-4-than in IL-2-producing cells.A solid and long-lasting tolerant state can be induced in adult mice by a single injection of deaggregated human gamma globulin (DHGG) 1 (for a review see reference 1). Although tolerance is induced in both T and B cells, the dose of tolerogen required for B cell tolerance is 2-3 log10 greater than that for T cell tolerance (for a review see reference 1). The tolerant state in T cells is of long duration, whereas in B cells it is of relatively short duration (2). Induction of tolerance in T cells is independent of the thymus and is not controlled by regulating T cells (3). Although the in vivo induction of tolerance in the T cells can be interfered with by generators of IL-1 or IL-1 itself (4, 5), once induced, the tolerant state cannot be terminated by these reagents. In addition to the in vivo induction of tolerance, tolerance has been induced in HGG-specific T cell clones using either DHGG (6, 7) or inappropriate antigen presentation (8-10). Whereas tolerance in Thl clones is induced in terms of both proliferation and T cell help, tolerance in Th2 clones is induced at only the T helper level (10, 11). Whether the in vivo induction of tolerance occurs in all CD4 + cell populations has recently been questioned. Data have been reported that imply that DHGG induces tolerance in IL-2-producing T cells, but induces responsiveness in IL-4-producing cells, resulting in IL-4 production and T helper activity (12).1Abbreviations used in tkis paper: DHGG, deaggregated human gamma globulin; HGG, human gamma globulin.In this report, the susceptibility of CD4 § cells and their subsets to the induction of tolerance to DHGG was assessed. Our results demonstrate that when mice are exposed to HGG as a tolerogen before immunization, such that the in vitro antigen-specific proliferation of CD4 + T cells is totally abrogated and serum antibody levels are dramatically reduced, antigen-specific proliferation of both Thl-and Th2-1ike subsets is abroga...

After a single intravenous injection of rabbits with aggregated HuIgG, IgM- and IgG-plaque-forming cells (PFC) in both the spleens and peripheral blood of rabbits peaked 5, 13, and 21 days after injection, while almost no PFC could be detected on days 8 and 16. The available data suggest that the secondary peaks of PFC (days 13 and 21) resulted from stimulation of memory cells by persisting antigen that was localized in the germinal centers in the spleen. No such persistence of antigen occurred in the lymph nodes, and these lymphoid tissues did not exhibit secondary peaks of PFC. The identical kinetic patterns for IgM- and IgG-PFC indicate that the major portion of IgG-PFC did not result from IgM-secreting cells switching to IgG synthesis and secretion. The present data suggest that the antibody produced and present at the site of interaction between committed cells and antigen is responsible for the regulation of antibody synthesis to persisting antigens. Possible cellular events involved in both the regulation and an apparent synchronous appearance of antibody producing cells in the spleens of rabbits were presented.

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