Activation of lymphocyte populations with concanavalin A or with lipoprotein and lipopeptide from the outer cell wall of Escherichia coli: correlation of early membrane changes with induction of macromolecular synthesis.

Abstract

The occurrence of early membrane changes following the interaction of mouse lymphocytes with the B‐lymphocyte mitogens, lipoprotein or lipopeptide, and with the T‐lymphocyte mitogen concanavalin A was compared to the induction of RNA and DNA synthesis induced by the mitogens in several lymphocyte populations. Membrane alterations were determined by measuring the incorporation of phospholipid precursors into phosphatidylcholine after the addition of the mitogens. It was shown that both B‐cell and T‐cell mitogens caused an increase in the incorporation of [14C]oleate and [14C]acetate in T B‐cell mixtures after 4 h of stimulation. The B‐cell mitogens, lipoprotein and lipopeptide, induced a marked incorporation of phospholipid precursors in spleen and lymph node cells of athymic mice. Corresponding to their cell specificity for the induction of macromolecular synthesis, no membrane changes were induced by the bacterial mitogens in thymocytes. On the other hand, the T‐cell mitogen concanavalin A was active in causing marked membrane changes in thymocytes. Remarkably, however, concanavalin A also induced the incorporation of phospholipid precursors in spleen and lymph node cells of congenitally athymic mice. Since membrane events in response to concanavalin A were not found after treating normal spleen and lymph node cells with anti‐Thyl serum and complement, the positive response observed in athymic mice probably resulted from the presence of pre‐T‐lymphocytes.Our results show that early alterations in membrane phospholipid metabolism in mature B or T lymphocytes are correlated with the subsequent induction of macromolecular synthesis, suggesting that these membrane changes are causally linked to cell activation. In addition the data suggest a similar molecular mechanism for the activation of lymphocytes by both T‐cell or B‐cell mitogens.