Interleukin-4 regulation of cytokine-induced HIV1 and interleukin-8 expression in promonocytic U1 cells is concentration- and cytokine-dependent.

IL4 has been shown to differentially modulate HIV1 replication in primary cells of the monocyte/macrophage lineage. Its effects on chronic HIV1 infection, however, are unknown. To address IL4-mediated effects on promonocytic cells chronically infected with HIV1, U1 cells were incubated in the presence or absence of IL4 together with cytokines that are known to induce both HIV1 and IL8 expression. IL4 enhanced IL1 beta-induced HIV1 and IL8 expression in promonocytic U1 cells, whereas it suppressed their expression induced by cytokines IL6, GM-CSF and to a small extent, TNF alpha. IL4 suppressed IFN gamma-induced IL8 production with increasing IL4 concentration, while HIV1 p24 core antigen production was suppressed at low IL4 input (0.1 and 1 U/ml) but was substantially enhanced at a high IL4 input concentration (10 U/ml). Results showed that the immunosuppressive cytokine IL4 can behave variably in modulating HIV1 and IL8 expression, depending on both the inducing cytokine and the input concentration of IL4.