Fyn fails to restore correct CD3ζ phosphorylation in Lck-deficient cells and is normally expressed in T-CVID T cells. (A, left) Immunoblot analysis of Lck and Fyn expression in parental JCaM1 cells and in stable transfectants expressing F505Lck or F528Fyn. (Right) Immunoblot analysis using antiphosphotyrosine antibodies of CD3ζ-specific immunoprecipitates from lysates of Jurkat cells, JCaM1 cells, or stable JCaM1 transfectants expressing F505Lck or F528Fyn. A small amount of tyrosine-phosphorylated CD3ζ in JCaM1 cells expressing Fyn was detectable at longer exposure times (data not shown). 0 indicates nonstimulated; CD3, activated by CD3 cross-linking with OKT3 mAb for 30 seconds at 37°C. The filter was stripped and reprobed with anti-CD3ζ mAb. (B) Anti-Fyn immunoblots of postnuclear supernatants of PBLs from patients with T-CVID (T-CVID1-4), 2 disease control patients (dis.ctr1 and 2), and a representative healthy control (ctr; n = 3). Filters were stripped and reprobed with antitubulin or antiactin mAb. Migration of molecular mass markers is indicated.