Abnormal pattern of tyrosine phosphorylation in unstimulated peripheral blood T lymphocytes from patients with systemic lupus erythematosus

Previous reports have shown abnormal responses mediated via the TCR/CD3 pat hway in T lymphocytes from systemic lupus erythematosus (SLE) patients. Rec ently, we and others have reported augmented TCR/CD3-mediated responses-in lupus T cells. It is possible that the pattern of downstream biochemical si gnals triggered by TCR/CD3 ligation may be altered in T lymphocytes from pa tients with SLE, thus leading to abnormal distal cell responses. In this pa per we have examined the phosphorylation of proteins on tyrosine residues i n peripheral blood T lymphocytes from a group of SLE patients and controls. We found a lower frequency of constitutively tyrosine-phosphorylated 119- and 113-kDa substrates and an enhanced frequency of tyrosine-phosphorylated 66- and 25-kDa proteins in unstimulated cultures of SLE T lymphocytes, sug gesting an altered pattern of tyrosine phosphorylation in T cells from pati ents in vivo. Additionally, the protein tyrosine phosphatase (PTP) activity of CD45 immunoprecipitates was lower in unstimulated lupus T cells and was enhanced after stimulation via the CD3 pathway in lupus but not control T lymphocytes. The present results seem to suggest abnormal regulation of in- vivo tyrosine phosphorylation in T cells from patients with SLE.