Phospholipid Metabolism of Stimulated Lymphocytes

Rabbit lymphocytes from the mesenteric lymph nodes were stimulated by phytohemagglutinin, concanavalin A and goat‐anti‐rabbit‐immunoglobulin serum or antibody. The synthesis of lecithin de novo was followed by incorporation of [ 14 C]choline. The turnover of the fatty acid moieties of individual lipids was measured by conversion of [ 14 C]oleate as well as [ 14 C]acetate. In resting lymphocytes the turnover of the long chain fatty acids of lecithin exceeded the synthesis de novo by a factor of 100. All three stimulants increased choline and oleate uptake to a similar extent starting very early after stimulation. Enhanced oleate incorporation began within 30 min after addition of a stimulant. Synthesis of long chain fatty acids and neutral lipids from acetate was raised similarly (between two‐ and six‐fold) when the lymphocytes were activated by the three stimulants. In contrast incorporation of acetate into phospholipids was much more increased during activation with phytohemagglutinin or concanavalin A than during activation with antiimmunoglobulin, resulting in stimulation indices of 32 (phytohemagglutinin, concanavalin A) and 9 (anti‐immunoglobulin) for lecithin. The relevance of the observed rapid changes in the membrane phospholipids for the mechanisms of lymphocyte activation is discussed.