CELLULAR IMMUNOLOGY 91,467-476 (1985) Regulation of IgG, and IgG2 Subclass Expression by Adjuvant- Activated Splenic Suppressor T Cells’ ILANA LGwu AND JACQUES THEE* Unite’ d’Immunog~&tique Cellulaire, Institut Pasteur, 25 rue du Docteur Roux, 75724 Paris, Cedex 15. France Received September 26, 1984; accepted November 27, 1984 Spleen cells from mice immunized with different adjuvants are able to suppress secondary in vitro IgG plaque-forming cell (PFC) responses. The suppressive effect is mediated by Lyt-Z positive T cells. IgG subclasses are affected differentially depending on the number of T suppressor (Ts) cells added in the assays.At low Ts cell concentration IgG2. and IgGzb PFC responses are selectively inhibited. At higher Ts cell concentration IgG, responses could also be completely inhibited, but IgA and IgM responses are not affected. Suppressor cells responsible for MS, WL and IgGzb suppression are never found in the draining lymph nodes of adjuvant-immunized animals. 0 1985 Academic Ress, Inc. INTRODUCTION Control of isotype expression is the subject of intense investigation at both the molecular(l) and cellular (2-6) level. We have been involved in assessing the role of The&r (TH)3 cells and for T suppressor (Ts) cells in the regulation of IgG subclass expression. Using prestimulated B cells we have shown that carrier-specific major histocompatibility complex (MHC)-restricted Tu clones can induce the production of IgG3, IgG,, IgG2, and IgG2b in secondary in vitro responses (7, 8). This result has been recently confirmed using B cells from unprimed animals (9). Therefore it seems that individual Tn cell clones can mediate the expansion and secretion of B cells producing different isotypes (6-9). This does not exclude the possible additional regulatory role of isotype-specific Tu cells or factors in isotype expression (6, 10-13). However we propose that the main regulatory influence on isotype expression, at least concerning IgG subclass expression, is carried out by suppressor mechanisms. We have indeed demonstrated the existence of such IgG Ts cells ( 14) and suppressor factors ( 15). ’ This work was supported in part by grants from the Institut National de la Sante et de la Recherche M&&ale (PRC 127021). ’ To whom correspondence should be sent. 3 Abbreviations used: B-P, Bordetella pertussis vaccine; BSS, balanced salt solution; C, complement; CFA, complete Freund’s adjuvant; DNP-OVA, dinitrophenylated derivative of OVA, GAT, terpolymer of L-ghttamic acid60, L-alanines”, r.-tyrosine’“; ip, intraperitoneal; id, intradermal; IBF, immunoglobulin binding factor; LNC, lymph node cells; M-P, Maalox and B pertussis vaccine; OVA, ovalbumin; PFC, plaque-forming cells; SC, spleen cells; SRBC, sheep red blood cells; TH, T helper cells; TNP, trinitrophenol; Ts, T suppressor cells. 467 0008~8749185 $3.00 Copyright 0 1985 by Academic Press, Inc. All rights of reproduction in my form reserved.