The use of T cell subtyping to distinguish rheumatoid arthritis from systemic lupus erythematosus.

The use of T cell subtyping to distinguish rheumatoid arthritis (RA) from systemic lupus erythematosus (SLE) was evaluated. We determined the distribution of IgG Fe receptor T cells (TG), IgM Fc receptor T cells (TM), and T cells lacking Fc receptors (Tnull) in 17 patients with RA and 7 patients with SLE. All RA patients including 3 antinuclear antibody positive-rheumatoid factor negative cases had normal numbers and percentages of TG, TM, and Tnull, whereas all SLE patients had a relative and absolute deficiency of TG. This TG lymphopenia was a better discriminator for SLE (7 of 7 SLE, 0 of 17 RA) than anti-DNA antibodies, hypocomplementemia, circulating immune complexes or total number of T cells.