Antigen-induced changes in phospholipid metabolism in antigen-binding B lymphocytes

Previous studies have demonstrated a marked change in the metabolism of phospholipids (PL) after activation of resting B lymphocytes with anti-immunoglobulin (anti-Ig). In this study we examined PL metabolism in highly purified trinitrophenyl (TNP)-binding B cells after their activation with various forms of TNP-carrier protein. Such cells show similar changes in PL metabolism when stimulated with either antigen or anti-Ig, i.e., increased incorporation of ³²PO₄ into phosphatidic acid and phosphatidyl inositol (PI) but not phosphatidyl choline, phosphatidyl ethanolamine, or phosphatidyl serine. We have demonstrated that these responses to antigen are TNP-specific and dose-related between 1 and 50 μg/ml, producing up to a 2.5-fold stimulation of ³²PO₄ incorporation into PI. The PL response is also directly related to the density of TNP on the carrier and can be augmented by additional cross-linking of the carrier protein. These data suggest that cross-linking of surface Ig by antigen induces a change in PL metabolism as an early event in B cell activation.