Soluble antigen profoundly reduces memory B-cell numbers even when given after challenge immunization.

Abstract

The splenic B-cell repertoire of unimmunized C57BL/6 mice can be examined for anti-(4-hydroxy-3-nitrophenyl)acetyl (NP) B cells of relatively high affinity by using a dual strategy. (14,15) and showed that it could prevent the generation of anti-HSA memory B cells in a dose-dependent manner. Adoptive transfer studies showed that the toleragen affected donor T and B cells, the former effect being more profound. Another way of studying the relative contributions of Tand B-lymphocyte populations to an antibody response is to make use of various hapten-carrier combinations (16-18). T-dependent anti-hapten antibody formation requires that anti-hapten B cells be "helped" by carrier-specific T cells. The anti-(4-hydroxy-3-nitrophenyl)acetyl (NP) response of C57BL/6 mice has been extensively investigated (19-21) because of the preferential appearance of B-cell clones utilizing the VH 186.2 V gene and the Al light chain gene, facilitating the study of V gene hypermutation. It is also a system in which clones making relatively high-versus relatively low-affinity antibody can be discriminated by the use of, respectively, relatively lowly versus relatively highly haptenated protein conjugates in an ELISA (22,23). In the present study, we immunized mice with highly haptenated NP-HSA, and attempted tolerance induction with lowly haptenated, freshly deaggregated, NP-HSA, with HSA carrier alone, or with NP attached to irrelevant carriers. The key findings were that NP-HSA .Jways worked better than carrier alone or NP attached i other carriers in preventing memory cell appearance and that tolerance could still be induced after immunogenic challenge, up to the time of the first appearance of V gene mutations. Apparently, the functional silencing of T and B cells is necessary for the full tolerance effect, and T-ceil help is still required for continued B-memory cell generation after the germinal center reaction is well under way.

Antigen-induced B cell apoptosis is independent of complement C4

“…This suggests that evolving memory B cells are the main target of apoptosis, and that by day 8 the antibody secreting cells have already left the germinal centre. This idea is supported by previous studies documenting reduced numbers of NP-specific memory precursor cells [21].…”

“…One proposed mechanism is antigeninduced apoptosis [18], whereby B cells whose receptors recognize a soluble, plentiful antigen die. Previous studies suggest that the application of a high dose of soluble antigen, before, during or after induction of an immune response against this antigen, induces a specific form of tolerance [21,25,26]. An experimental model for these events is the suicide experiment (injection of a high dose of antigen during an established immune response against the antigen [18][19][20]).…”

“…Previous studies have shown that the injection of a high dose of soluble antigen, during an established primary immune response (suicide experiment), induces massive apoptotic death in germinal centre B cells [18][19][20]. Furthermore, reduced levels of 4-hydroxy-3-nitrophenylacetyl (NP)-binding IgG1 + B lymphocytes, originating from the germinal centre, as well as NP-specific memory precursor cells, have been reported after this treatment [21]. However, it is not clear if NP-specific antibody production is inhibited completely during the suicide experiment.…”

A form of immunologic tolerance through impairment of germinal center development.

“…The focus of attention of these studies was the higher-affinity B cells generated in non-tolerant mice after strong T-celldependent challenge, the appearance of which was markedly diminished, as assessed by enumeration of antibody-forming cell precursors capable of forming specific IgGl antibody. This form of tolerance within the secondary B-cell repertoire was due to effects on both the T-and the B-cell compartments, although the former effect was more important (10 (Fig. 1A).…”

“…We have previously explored immunologic tolerance in adult mice by using soluble, deaggregated human serum albumin (HSA) (9) or (4-hydroxy-3-nitrophenyl)acetyl (NP) coupled to HSA (NP-HSA) (10) to lower responsiveness. The focus of attention of these studies was the higher-affinity B cells generated in non-tolerant mice after strong T-celldependent challenge, the appearance of which was markedly diminished, as assessed by enumeration of antibody-forming cell precursors capable of forming specific IgGl antibody.…”