Do gamma delta T cells play an important role in autoimmune disease?

A T cell subpopulation using an alternative receptor heterodimer (gamma delta T cells) contributes 0.5-10% to the T cell population in the normal peripheral blood. One subset of gamma delta T cells (V gamma 9+/V delta 2+/ C gamma 1) preferentially recognizes mycobacterial antigens, which are the triggering antigens in the rat adjuvant arthritis (AA), an animal model with some similarities with rheumatoid arthritis (RA). Here we summarize data on the prevalence of gamma delta T cells in peripheral blood, synovial fluid and synovial membranes of RA patients which show that gamma delta T cells, in particular the subset reactive with mycobacterial antigens in normal individuals, are rare in all studied compartments. Furthermore, there was no enrichment of gamma delta T cells in the peripheral blood of patients with ankylosing spondylitis or systemic lupus erythematosus, autoimmune diseases with involvement of the joints. In the AA model depletion of the "conventional" alpha beta T cells completely prevented the induction of the disease and very effectively improved ongoing arthritis even though substantial numbers of gamma delta T cells were present in these animals. Taken together, our data do not support the notion of a significant contribution of gamma delta T cells to chronic joint inflammation in the autoimmune diseases studied or in adjuvant arthritis.