RECIPIENT POLYCLONAL B-CELL ACTIVATION AND IMMUNOGLOBULIN PRODUCTION INDUCED BY PRIMING WITH A RETROVIRAL SUPERANTIGEN

The superantigen vSAG-7 (or MIs 1(a)) is a membrane glycoprotein encod ed by the endogenous retrovirus mouse mammary tumor virus 7 (MMTV-7) a nd is highly stimulatory for V beta 6/CD4(+) T cells, Priming of adult MMTV-7-negative mice with vSAG-7-expressing cells initially results i n the activation of the peripheral V beta 6/CD4(+) T cell compartment and is followed by T cell tolerance to the superantigen, During the co urse of tolerance induction the number of recipient B lymphocytes incr eases in the lymph nodes, but not the spleen, of vSAG-7-primed recipie nts, These B cells also express increased levels of class II MHC and p resent passively acquired superantigen, In this study we asked if thes e effects on the host B cell compartment are followed by the productio n of immunoglobulin. Priming of MMTV-7-negative BALB/c or CB.17 mice w ith vSAG-7-expressing cells from DBA/2 mice induced increases of both IgM and IgG(2a), in the serum, Use of Igh congenic CB.17 (IgM(b)) mice as recipients of the vSAG-7-presenting cells from DBA/2 (IgM(a)) dono rs indicated that the IgM and IgG produced were entirely of host origi n, Priming with vSAG-7 also amplified (four- to fivefold) the antibody -producing cell response induced to a suboptimal dose of sheep RBC. Pr iming with purified B cells from vSAG-7 donors resulted in recipient V beta 6/CD4(+) T cell activation and increased numbers of recipient B cell in the lymph nodes, but did not induce immunoglobulin production. In contrast, priming with purified CD8(+) T cells resulted in increas ed quantities of serum IgM but not vSAG-7-reactive T cell activation o r increased numbers of recipient B cells in the lymph nodes, These res ults indicate that the T cell activation and increased B cell number w ith upregulated class II MHC expression initially observed following v SAG-7 priming of adult MMTV-7-negative recipients are not linked to th e induction of the recipient-derived immunoglobulin production. (C) 19 96 Academic Press, Inc.