Immunoglobulin C‐gene expression. III. Possible induction of specific genetic events in activated B lymphocytes by the polyclonal stimuli driving clonal expansion

摘要

AbstractPolyclonal activation of resting B lymphocytes by either lipopolysaccharide or specific helper cells recognizing antigens on B cell membranes results in selective patterns of IgG subclass expression among plaque‐forming cells. We have studied the IgG subclasses of plaque‐forming cells generated in cultures of purified B cell blasts selected for reactivity to either LPS or helper cells, and restimulated by either lipopolysaccharide, specific helper cells, or as “bystanders”, by nonspecific B cell growth factors. Development of IgG1plaque‐forming cells is observed only when clonal expansion is maintained by specific helper cells, whereas IgG3secretion specifically requires stimulation by lipopolysaccharide and the absence of helper cell activity. Furthermore, exposure of resting B lymphocytes to specific helper cells induces, in 48 h, an irreversible loss of the potential to produce IgG3. Other than showing that helper cell‐dependent B cell growth and maturation is more complex than previously suspected, these results suggest that differentiation signals or factors induce specific DNA recombination and dele