CROSS-REACTIVITY OF IGM-SECRETING AND IGG-SECRETING B-CELLS IN MURINECHRONIC GRAFT-VERSUS-HOST REACTION

A chamber ELISpot assay was used to measure the frequency with which i n vivo activated B cells secreted crossreactive antibodies during a ch ronic graft-versus-host reaction in mice. Both normal (C57BL/10 x DBA/ 2)F1 mice and F1 recipients of syngeneic spleen cells (SynF1) expresse d repertoires in which 13-17% of IgM and 3-5% of IgG-secreting cells w ere cross-reactive. By comparison, 43-55% of IgM and 9-40% of IgG-secr eting cells from F1 recipients of parental DBA/2 spleen cells (GVHF1) were cross-reactive (P < 0.01, GVHF1 versus F1 or SynF1). The cross-re activity of the GVHF1 IgM secreting cells remained elevated for >2 mon ths following cell transfer. In contrast, the crossreactivity of IgG-s ecreting cells, which was significantly high at Week 3 post-transfer, declined to nearly normal levels by Week 9. These findings demonstrate that crossreactive B cells constitute an abnormally large fraction of the repertoire expressed by mice with chronic GVHR in a period when B cell hyperstimulation was occurring. (C) 1994 Academic Press, Inc.