Changes in phospholipid metabolism during B lymphocyte activation

We have examined phospholipid metabolism in murine B lymphocytes stimulated with anti-Ig bound to Sepharose. T cell-depleted splenic B lymphocytes cultured with Sepharose-coupled, affinity-purified goat anti-mouse Ig (GAMIg) increased the incorporation of ³²PO₄ into phosphatidic acid and phosphatidylinositol within 3 hr and increased [³H]-thymidine uptake at 48 hr. No increase in labeling was observed in phosphatidylethanolamine, phosphatidylcholine, or phosphatidylserine. Based on both negative and positive selection procedures, it was demonstrated that these responses occurred in B lymphocytes. In contrast to the thymidine uptake response of the GAMIg-stimulated B lymphocytes, the phospholipid response did not require the presence of accessory cells or exogenous-cytokines. The same selective changes in phospholipid metabolism were observed in neoplastic B lymphocytes (BCL₁) after treatment with Sepharose anti-μ, but not with Sepharose anti-Ia or Sepharose normal Ig. The dose-response relationships of ³²PO₄ incorporation into phosphatidic acid and phosphatidylinositol and [³H]thymidine uptake were nearly identical in BCL₁ cells. The results of these experiments indicate that interaction of B lymphocytes with insolubilized anti-Ig results in prompt and selective changes in phospholipid metabolism that appear to be correlated with B lymphocyte proliferation.