Lymphopenia in Sjögren's syndrome with rheumatoid arthritis: relationship to lymphocytotoxic antibodies, cryoglobulinemia, and impaired mitogen responsiveness.

Lymphocyte subpopulation studies in 21 patients with Sjögren's syndrome and rheumatoid arthritis revealed an absolute lymphopenia and a normal percentage of T- and SIg-cells. In one patient, a large percentage of lymphocytes bore both IgG and IgM; after cell trypsinization only IgM was resynthesized. This surface IgM was capable of binding human IgG, suggesting that the presence of multiple classes of immunoglobulins on the surface of these lymphocytes was due to surface rheumatoid factor activity. Profound lymphopenia was associated with high concentrations of cryoglobulins and the presence of lymphocytotoxic antibodies. These antibodies were broadly reactive, causing cytotoxicity of T- and SIg-cells from normal subjects, from viral and lymphoproliferative disease subjects, from different organs, and SIg-cells from human lymphoblastoid cell lines. Lymphocyte transformation after phytohemagglutinin and pokeweed mitogen stimulation was impaired in comparison to normal subjects. Warm washing of the lymphocytes and purification to greater than 80 per cent T-cells did not restore mitogen responsiveness to normal, suggesting that cell coating by an antibody and diminished responder cell number were inadequate explanations for the impaired transformation.