Phospholipid metabolism of stimulated lymphocytes. Composition of phospholipid fatty acids.

Lymph node lymphocytes and thymocytes from different species were isolated. Rabbit and calf thymocytes were stimulated in vitro with concanavalin A. Phospholipid fatty acids of these cells were analyzed and their positional distribution was determined. When compared with liver, phosphatidylcholine of unstimulated lymphocytes was found to contain relatively high amounts of palmitic acid in position 2 and oleic acid in position 1. After stimulation of rabbit thymus cells, the content of polyunsaturated fatty acids (linoleic and arachidonic acid) increased. Thus the ratio of polyenoic acids (18:2 + 20:4) to saturated fatty acids was doubled when compared to control cells. Similar results were obtained after in vivo stimualtion with Mycobacterium Calmette Guerin. The correlation of these findings with the activation of acyl-CoA:lysolecithin acyltransferase, and their relevance for changes of membrane fluidity during lymphocyte stimulation is discussed.