Inhibition by lactate dehydrogenase-elevating virus of in vivo interleukin 4 production during immunization with keyhole limpet haemocyanin.

Interleukin 4 (IL-4) and gamma interferon (IFN-gamma) gene expression in lymph node cells from mice immunized with keyhole limpet haemocyanin in the presence of complete Freund's adjuvant was analysed by polymerase chain reaction. This immunization clearly induced the expression of IL-4 message, whereas IFN-gamma message was only slightly increased. A concomitant infection with lactate dehydrogenase-elevating virus drastically decreased IL-4 expression whereas IFN-gamma message was not modified. Analysis of the kinetics of cytokine production indicated that the virus did not induce a mere change in the timing of lymphokine production, but a persistent inhibition of IL-4.