Secretion of IgG1 induction factor by T cell clones and hybridomas.

IgG1 induction factor elevates the IgG1 response induced by lipopolysaccharide and suppresses the lipopolysaccharide-induced IgG3 and IgG2b responses in cultures of mouse spleen cells. We have developed new T cell lines secreting this factor by cloning mixed lymphocyte culture populations. Using supernatants of one of these T cell lines it was found that the assay is quantitative, reproducible and accurate, both when induction of IgG1 as well as reduction of IgG3 and IgG2b were measured. Using this analysis, different conditions to induce maximal production of the factor were tested. The cell line was thereafter used as fusion partner with a T cell lymphoma. The hybrids were selected in the presence of T cell growth factor and all of them secreted IgG1 induction factor.