Analysis of human T cell and B cell responses against U small nuclear ribonucleoprotein 70-kd, B, and D polypeptides among patients with systemic lupus erythematosus and mixed connective tissue disease

Objective. To analyze T and B cell reactivity with U small nuclear RNP (snRNP) 70-kd, B, and D polypeptides among patients with connective tissue disease (CTD) and to examine the functional characteristics of snRNP-reactive T cell clones. Methods. We used an snRNP enzyme-linked immunosorbent assay and immunoblotting to characterize antibodies in patients' sera, We used human recombinant fusion proteins 70 kd, B, and D to stimulate and clone snRNP-reactive T cells from CTD patients, We analyzed the cell surface phenotype, antigenic specificity, and cytokine profiles of T cell clones. Results. Patients showed T cell responsiveness to snRNP polypeptides that paralleled their autoantibody reactivities. A total of 256 clones were generated, and clones were identified which were specific for the 70-kd, B, or D polypeptides. Clones expressed a T helper cell phenotype, and were found to produce substantial quantities of both interleukin-4 (IL-4) and interferon-gamma, and lesser quantities of IL-2 and IL-6, Conclusion. These results show that CTD patients have clonable circulating snRNP-reactive T cells that parallel the specificity of snRNP-reactive antibodies in their sera, The snRNP-reactive T cells exhibit a helper cell phenotype and produce cytokines which are important in B cell help and differentiation.