RELEASE OF ARACHIDONIC-ACID FROM HUMAN-LYMPHOCYTES IN RESPONSE TO MITOGENIC LECTINS

After exposure to mitogenic lectins in vitro, human mononuclear cells (95% lymphocytes) that were prelabeled with [14C]arachidonic acid rapidly released a portion of their radioactivity in the medium. Most of the released radioactivity was free arachidonic acid. Although other sources were not excluded, the most important source of cell-bound radioactivity in the release reaction appeared to be phosphatidylinositol, suggesting that at least part of the response is occurring through an increase in phospholipase A2 activity. By gas liquid chromatography other fatty acids were also released, but there was considerable selectivity in the response for arachidonic acid. The response was dependent on the availability of free Ca2+ in the medium and was enhanced by serum proteins and unlabeled arachidonic acid. Most of the response appeared to be from the lymphocytes themselves rather than from contaminating cells. The rapid generation of free arachidonic acid in response to mitogenic lectins suggests a possible role for arachidonic acid metabolities in the activation process.