Impaired antigen receptor induced calcium mobilization in a phospholipase C-γ₁ deficient B cell line

B lymphocytes express phospholipase C-γ₁ (PLC-γ ₁) and phospholipase C-γ₂ (PLC-γ₂) isozymes. However, the relative importance of these two isozymes in B cell signaling is not known. We report here the identification and analysis of a B cell line deficient in PLC-γ₁. Mature splenic B lymphocytes and a panel of cell lines representing pre-B, immature and mature B cell stages expressed phospholipase C-γ (PLC-γ), but not the β or δ isoforms of phospholipase C (PLC). While all the tested B cell lines and primary splenic B cells expressed PLC-γ₁ and PLC-γ ₂ isozymes, the L1.2 B cell line exclusively expressed PLC-γ₂, but not PLC-γ₁ isozyme. The PLC-γ₁ deficient L1.2 B cells expressed levels of surface IgM comparable to that of PLC-γ₁ positive 70Z/3 B cell line. However, stimulation through the antigen receptor induced Ca⁺⁺ response in 70Z/3, but not L1.2 B cells, suggesting a requirement for PLC-γ₁ in antigen receptor induced Ca⁺⁺ signaling in these cells. The possible use for L1.2 cells in testing the regulation of PLC-γ₁ and PLC-γ₂ dependent calcium mobilization in B lymphocytes is discussed.