Anti-IgM treatment influences immunoglobulin heavy and light chain mRNA levels in mitogen-stimulated B lymphocytes.

The mechanism by which soluble anti-IgM inhibits plaque formation by lipopolysaccharide-stimulated B cells was investigated. Since lower amounts of immunoprecipitable mu heavy and kappa light chains were found in cell lysates, this indicated that soluble anti-IgM was inhibiting not only secretion. Subsequently, Northern blot analysis of poly(A+) RNA showed that the steady state levels of mRNA for immunoglobulin heavy and light chain from B cells stimulated with lipopolysaccharide were reduced if the cultures were treated with soluble anti-IgM. The steady-state levels of class I major histocompatibility complex antigen RNA were unaffected by anti-IgM treatment. Addition of supernatants from mouse spleen cells stimulated with concanavalin A at day 2 of culture partially reversed the effect of soluble anti-IgM on immunoglobulin expression.