C-myc expression in lymphocytes of MRL/MP-lpr mice activated by A23187 and TPA.

In order to analyse the molecular mechanism of lymphocyte activation defect in MRL/MP-lpr (MRL/1) mice, c-myc proto-oncogene expression was examined in MRL/1 lymph node cells stimulated by various agents. Since a transient increase of c-myc RNA in early hours is required for lymphocyte activation, detection of c-myc messenger RNA is useful to determine whether or not an appropriate signal is transduced to the nucleus. Stimulation by concanavalin A (Con A) plus 12-O-tetradecanoyl phorbol 13-acetate (TPA) or A23187 plus TPA markedly increased c-myc mRNA expression and cell proliferation, whereas stimulation by Con A alone failed to do so. These results suggest that an abnormality exists in the early signal transduction process, and that it could be bypassed by calcium influx and direct activation of protein kinase C.