Selective effects of cholera toxin on the activation of mouse B cells by different polyclonal activators

摘要

AbstractMurine B cells were stimulatedin vitrowith anti‐immunoglobulin (Ig) antibodies, lipopolysaccharide, or with various combinations of phorbol dibutyrate and ionomycin. Very low concentrations (ca. 10−14M) of cholera toxin inhibited anti‐Ig‐stimulated DNA synthesis, while the response to LPS was only abrogated by 2 × 104‐105‐fold greater concentrations of the toxin. Earlier responses in anti‐Ig‐stimulated B cells, such as increases in Ia antigen levels, were not affected by the toxin. Protein kinase C‐activating phorbol esters, together with Ca2+ionophores, are believed to stimulate DNA synthesis in lymphocytes by mimicking the two second messengers resulting from ligation of the antigen receptors. However, concentrations of cholera toxin which totally abolish anti‐Ig‐induced B cell proliferation significantly enhanced DNA and RNA synthesis induced by phorbol dibutyrate plus ionomycin. The results are discussed in terms of possible effects of cholera toxin on guanine nucleotide‐binding (G) proteins controlling receptor coupling to second messenger‐gen