In situ characterization of mononuclear cells in rheumatoid tissues, using monoclonal antibodies. No reduction of T8-positive cells or augmentation in T4-positive cells.

The reactivity of monoclonal mouse anti-human antibodies specific for mononuclear cell surface antigens were studied by the indirect immunofluorescence technique in frozen synovial tissue sections from patients with rheumatoid arthritis (RA). Most of the proliferating synovial lining cells were positive for HLA-DR antigens and monocyte-specific antigens, since they reacted with the OKIa1 and OKM1. Cells positive for HLA-DR and monocyte antigens were also seen scattered or in small nests in the synovial stroma, probably representing synovial cells or monocytes/macrophages. Some of the HLA-DR-positive cells may also be B lymphocytes or activated T cells. Endothelial cells were also HLA-DR antigen-positive. Monoclonal antibodies with specificity for all T cells (OKT3), for helper/inducer cells (OKT4), and for suppressor/cytotoxic cells (OKT8) reacted with cells often located in follicle-like structures around vessels. Cells with the T4 phenotype tended to be located in the centre of the follicles, whereas the T8 positive cells were more peripherally situated. In most instances fewer cells were positive for the T8 than for the T4 marker. In some instances there was as many T8-positive cells as T4-positive cells. Complete lack of T-lymphocyte subpopulations was not seen.