Expression of HL‐A Antigens on the Surface of Cultured Human Lymphoid Cells: Effect of Inhibitors of Protein and Nucleic Acid Synthesis

Cultured human lymphoid cells (WI‐L2), when incubated in mid‐log phase with different concentrations of puromycin, showed a 70% decrease in the expression of HL‐A antigens on their surface as measured by quantitative microabsorption. This decrease in surface antigen expression was accompanied by a marked inhibition of the rate of incorporation of 14C leucine into cellular polypeptides suggesting a correlation between protein synthesis and HL‐A antigen expression on cultured human lymphoid cells. The inhibitory effects of puromycin on HL‐A expression were reversible. Actinomycin D did not affect HL‐A antigen expression, suggesting that the messenger RNA coding for these antigens is relatively long‐lived. Cytosine arabinoside, 5‐bromodeoxyridine, ethidium bromide and rifampicin did not affect HL‐A antigen expression. By contrast, cycloheximide at a concentration which inhibited the rate of polypeptide synthesis by at least 95% did not change HL‐A antigen expression. The differential effects of puromycin and cycloheximide on the synthesis of HL‐A polypeptides are similar to the effect of these drugs on mitochondrial protein synthesis.