Regulation of hybridoma B-cell proliferation by immunoglobulin-binding factor

Immunoglobulin-binding factors (IBF), which are cytokines able to suppress the immunoglobulin production by normal and transformed B cells, have been tested for their ability to interfere with hybridoma B-cell growth. Coculture experiments performed in soft agar between hybridoma B cells and hybridoma T cells secreting IgG-BF indicated that IgG-BF act as a growth regulatory molecule able to inhibit strongly the development of hybridoma B-cell colonies; this cytostatic effect, which appeared not to be a direct cytotoxic effect, was confirmed when using semi-purified IgG-BF in both soft agar and liquid medium cultures of hybridoma B cells. Thus, IBF appear to act as both immunoregulatory and growth regulatory factors. Some of the molecular consequences of this dual effect and its possible role in certain B-cell lymphoproliferative diseases such as multiple myeloma are discussed.