Lymphocyte subsets in a large cohort of patients with systemic lupus erythematosus.

In search of markers of disease activity in patients with SLE we have investigated blood lymphocyte subsets from a large cohort of patient. Seventy-one patients were studied using a well-defined panel of fluorescent monoclonal antibodies which recognize the major T, B and NK lymphocyte subsets and activated cells. Flow cytometry was used with standard automated software. Overall, SLE patients were lymphopenic. The proportion of activated T cells was increased and NK cells were decreased in both proportion and absolute numbers (P < 0.001). This decrease was more pronounced in the more active patients. None of the T cell activation markers was shown to distinguish different degrees of disease activity. However, the percentage of NK cells was significantly reduced in active disease states (P < 0.01). Decreased numbers of NK cells could potentially reduce the resistance of SLE patients to infectious organisms.