Immunologic aspects of psoriasis. III. Fc-gamma-receptor bearing mononuclear cells in peripheral blood.

An anti-IgG activity has previously been reported at the cellular level in patients with psoriasis. This activity was demonstrated by the so-called 'rheumatoid' rosette test. In the present work the nature of 'rheumatoid' rosette-forming cells was studied in comparison with other EA rosette techniques. The use of purified cell populations showed that the lymphocytes participating in the 'rheumatoid' rosette phenomenon were lacking conventional T and B cell membrane markers, and were thus referred to as null cells. Such mononuclear cells bearing a receptor for the Fc part of IgG were able to act as killer cells to IgG-coated target cells. The cytotoxic activity was mainly restricted to a small proportion of lymphocytes forming 'rheumatoid' rosettes which had a high avidity for EA complexes. Such cytotoxicity could contribute to the aetiology of lesions in psoriasis.