Interleukin 8 (IL-8) inhibits the interleukin 4 (IL-4)-induced but not the spontaneous growth of human B cells via mechanisms that may involve protein kinase C.

IL-8 inhibited the IL-4-induced but not the spontaneous growth of both a human B cell line, CBL, and in vivo activated B cells. This inhibition was specific to IL-8, since anti-IL-8 mAb, but not control IgG1, blocked inhibition. Phorbol 12, 13 dibutyrate did not affect the IL-4-induced B cell growth; however, it reversed the IL-8-mediated inhibition, and this reversal was blocked by H7 (a protein kinase C inhibitor), but not by H8 (a protein kinase A inhibitor). These results indicate that IL-8 inhibits IL-4-induced B cell growth via specific mechanisms that may involve protein kinase C.