Dynamics of Membrane Fatty Acids During Lymphocyte Stimulation by Mitogens

When antigens or mitogens bind to the surface of lymphocytes, a sequence of metabolic events is triggered leading to proliferation of the cells and to the expression of new functions. Several studies showed (Greaves and Bauminger, 1972; Betel and van den Berg, 1972; Andersson et al., 1972) that binding of the stimulating ligands on the plasma membrane is sufficient to activate the cell. Consequently one can assume that the activation is initiated by processes which occur in the outer cell membrane. However, it is difficult to establish a single sequence of events since a variety of changes obviously occur in the plasma membrane during the early phase of the activation. Thus the permeability for nucleosides (Peters and Hausen, 1971a) sugars (Peters and Hausen, 1971b) and amino acids (Mendelsohn et al., 1971; van den Berg and Betel, 1973) or ions such as K+ (Quastel and Kaplan, 1971) or Ca++ (Whitney and Sutherland, 1972) is increased. Since many of these functional changes are transient events it seems necessary to find mechanisms which lead to stable structural changes of the outer cell membrane. In the past, we have described changes of phospholipids which are connected with the activation process and lead to structural changes of the plasma membrane.