Immunoglobulin C‐gene expression. I. The commitment to IgG subclass of secretory cells is determined by the quality of the nonspecific stimuli

Abstract

Polyclonal stimulation of normal splenic B lymphocytes with either lipopolysac-charide (LPS) or helper T lymphocytes specific for B cell surface antigens results in the selective expression of IgG subclasses by the secretory cells: in addition to IgM-secreting plaque-forming cells (PFC), thymus-independent stimulation leads to the development of IgG₂ and IgG₃ PFC, while helper cell-dependent activation leads to IgG₁ and IgG₂ PFC. This cannot be solely explained by selective stimulation of distinct B cell subpopulations, because purified LPS-reactive blasts if restimulated by helper cells switch to IgG₁ while if maintained with LPS switch to IgG₃. The simultaneous stimulation of splenic B cells with LPS and helper cells results in additive IgM and IgG₂ responses, but in the selective suppression of IgG₃ PFC with a concomitant synergic enhancement of IgG₁ responses. These results are interpreted to indicate that the expression of IgG C genes in proliferating B lymphocytes is directed by the quality of nonspecific stimuli.