Suppressive B-cell factor (SBF) produced by FcR-bearing B cells; suppression of B, but not non-B-cell proliferation.
B cells that have receptors for the Fc portion of IgG (FcR gamma + B cell) elaborate an immunoregulatory lymphokine termed suppressive B-cell factor (SBF) after binding immune complexes, such as sheep erythrocytes sensitized with IgG anti-sheep erythrocyte antibody (EA). For producing SBF, de novo protein is required, but not DNA or DNA-dependent RNA synthesis. This mediator is released into the culture supernatant of FcR gamma + B cells during 6 to 48 hr after stimulation by EA. SBF suppresses the proliferation of B, but not non-B cells. Thus, it suppressed (i) plaque-forming cell responses in the induction phase in an antigen-non-specific manner, (ii) DNA synthesis of lipopolysaccharide-activated B cells, but neither concanavalin A nor phytohaemagglutinin-activated T cells, and (iii) the proliferation of B but not non-B tumour-cell lines by acting at the G1-S junction in the cell cycle. Concordance of H-2 haplotype between SBF-producing mice and target B cells is necessary for the suppression. Thus, the action of SBF is B-cell specific and antigen-non-specific. Immune complex-mediated negative feedback regulation seems to be operated by lymphokines such as SBF which may be also involved in the surveillance for B-cell tumours.
D000818:Animals; D000917:Antibody Formation; D001402:B-Lymphocytes / Q000166:cytology / Q000276:immunology*; D002453:Cell Cycle; D002455:Cell Division; D002460:Cell Line; D004247:DNA / Q000096:biosynthesis; D005260:Female; D006462:Hemolytic Plaque Technique; D008222:Lymphokines / Q000378:metabolism*; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D008934:Mitogens / Q000494:pharmacology; D011961:Receptors, Fc
D008222:Lymphokines; D008934:Mitogens; D011961:Receptors, Fc; D004247:DNA