The difference in p53 antioncogene transcription in human monocytes and lymphocytes

The p53 gene is associated with malignant transformation as well as 'antioncogene' activity. In this report expression of p53 in resting and activated human blood monocytes and lymphocytes was studied. It is shown that human monocytes freshly isolated by continuous Percoll-gradient centrifugation contain detectable levels of p53 mRNA. Stimulation of monocytes by the potent activation inducer Staphylococcus aureus Cowan I (SAC) for 3-5 h caused the disappearance of p53 mRNA. In contrast, induction of a high level of tumor necrosis factor alpha mRNA was detected. The addition of cycloheximide did not increase the p53 mRNA content in stimulated monocytes, and decreased the mRNA level in resting cells. p53 mRNA was absent in freshly isolated lymphocytes and in resting cells cultured for 20 h. Activation of lymphocytes by phytohemagglutinin caused accumulation of p53 mRNA. We suggest that p53 gene regulation and functions might be different in human monocytes and lymphocytes.