THE EFFECT OF CIRCULATING SERUM FACTORS FROM PATIENTS WITH SYSTEMIC LUPUS-ERYTHEMATOSUS ON PROTEIN KINASE-A (PKA) ACTIVITY AND PKA-DEPENDENT PROTEIN-PHOSPHORYLATION IN T-LYMPHOCYTES

T lymphocytes from subjects with active systemic lupus erythematosus (SLE) exhibit reduced cAMP-inducible, protein kinase A (PKA)-dependent phosphorylation of several intracellular substrates compared with healthy and disease controls. To ascertain whether the persistent T cell activation observed during active SLE can result in impaired PKA-dependent protein phosphorylation, normal T cells were activated in vitro by monoclonal anti-CD3-ε {lunate} antibody and recombinant IL1-α (rIL1-α) for 24 hr. T cell activation, verified by IL2 mRNA, IL2 receptor-α (IL2R-α) mRNA, and IL2R-β mRNA expression, did not diminish cAMP-inducible, PKA-dependent protein phosphorylation. We also tested the hypothesis that circulating factors present in active SLE serum can decrease cAMP-inducible total PKA phosphotransferase activity and PKA-dependent protein phosphorylation in normal T lymphocytes. T cells cultured for 24 hr in medium supplemented with 10% active SLE sera (from subjects who exhibited the defect of PKA-dependent protein phosphorylation) exhibited similar total PKA phosphotransferase activity and substrate phosphorylation as cells cultured in normal AB serum. Moreover, the addition of interferon-α (IFN-α) and/or immune complexes (IC) did not diminish either total PKA activity or PKA-dependent substrate phosphorylation. Lastly, we found that the defect of PKA-dependent protein phosphorylation in active SLE T cells could not be reversed by culturing the cells in culture medium supplemented with 10% AB serum for 24 hr. In conclusion, (a) deficient cAMP-inducible, PKA-dependent phosphorylation in SLE T cells is not reversible by culturing cells in vitro; (b) there is no evidence to support the concept that serum factors, including IC and IFN-α, can induce a defect of PKA-dependent protein phosphorylation in normal T cells. © 1993 Academic Press, Inc.