Interleukin-4 stimulates immunoglobulin secretion by Epstein-Barr virus (EBV)-activated tonsillar B cells,and by EBV-transformed lymphoblastoid B cell lines without increasing cell division

Summary Freshly prepared Epstein-Barr virus-transformed B lymphoblastoid cell lines derived from five different donors were tested for their responses to recombinant human interleukin-4 and to low molecular weight B cell growth factor. In the absence of either cytokine, all five lines secreted immunoglobulin of more than one isotype (IgM, IgG, and IgA, but not IgE). Stimulation with interleukin-4 resulted in a significant increase in immunoglobulin secretion, but did not enhance cell division measured by tritiated-thymidine uptake or cell counts. In contrast, low molecular weight B cell growth factor increased both immunoglobulin secretion and cell division. The increase in immunoglobulin secretion stimulated by interleukin-4 occurred for each of the different isotypes (IgM, IgG and IgA) produced by the unstimulated line. No IgE secretion was detected for any of the five lines. It was also found that low (5 units/ml), but not high (100 units/ml), concentrations of interleukin-4 increased IgM, IgG and IgA secretion by tonsillar B cells polyclonally activated with Epstein-Barr virus. Again, no IgE was detected at any time. These results suggest that interleukin-4 can function as a late-acting B cell differentiation factor as well as a growth factor for human B cells.