CD4+ T-lymphocytes require two signals to become activated--antigen receptor (TcR) occupancy and an antigen-presenting cell (APC)-derived costimulus. The latter may be provided by B7.1 (CD80) or B7.2 (CD86) on APC interacting with CD28 on T-cells. We have studied the expression of these costimulatory molecules in rheumatoid and osteoarthritic synovial membrane. Very few B7.1-positive cells were seen in synovial tissue from either established or early rheumatoid disease, or in rheumatoid arthritis (RA) or osteoarthritis (OA) synovia at arthroplasty. In contrast, B7.2 was readily detected in rheumatoid synovia, predominantly in the lining layer, in a pattern of expression that corresponded to the presence of CD68-positive macrophages. Only occasional B7.2-positive cells were seen in OA synovia. The presence of B7.2 but the relative lack of expression of B7.1 may be partly responsible for the observations of 'frustrated' T-cell activation or T-cell hyporesponsiveness in the rheumatoid synovium.

Objectives-To examine the distribution offour annexins in non-inflamed rheumatoid arthritic and osteoarthritic synovial tissue. Methods-Frozen sections were stained with monoclonal antibodies (MAb) specific for annexins-I, -II, -IV, and -VI, and for cell lineage related markers including CD68 and CD14 (macrophages), prolyl hydroxylase (fibroblasts), and CD3 (T cells).

We have investigated whether the skin-homing T lymphocytes identified by the cutaneous lymphocyte antigen (CLA) are increased in the synovial membrane of patients with psoriatic arthritis. Twenty-six synovial samples (13 psoriatic arthritis, seven rheumatoid arthritis, six osteoarthritis) were obtained from involved knees. Lesional skin biopsies were taken from nine of the patients with psoriatic arthritis and six patients with psoriasis alone. All samples were single- and dual-stained for CLA and CD3 (to identify T lymphocytes) using HECA-452 (anti-CLA) and anti-CD3 monoclonal antibodies. E-selectin expression was also determined. The percentage of dual-stained lymphocytes was significantly greater in psoriatic skin than in synovium (P < 0.001) and similar between psoriatic and rheumatoid synovium. There was no significant difference in the percentages of CLA-positive cells in psoriatic skin in patients with psoriatic arthritis compared with psoriasis alone. The intensity of endothelial E-selectin expression was significantly greater in skin psoriasis than in synovium (P < 2 x 10(-5)), and rheumatoid synovium had significantly greater expression than psoriatic synovium (P < 0.05). However, there was no significant correlation between E-selectin expression and the percentages of CLA-positive lymphocytes. This study provides further evidence that the CLA antigen is enriched on skin-homing lymphocytes. Conversely, the link between skin and joint inflammation in psoriatic arthritis does not seem to be explained by increased trafficking of CLA T cells to psoriatic synovium.

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