The presence of CD5LOW+NK cells in normal controls and patients with pulmonary tuberculosis.

CD5 antigen is present on all normal alpha beta T cells and some B cells. Human NK cells do not usually express CD5 antigen, but we found a subset of CD5LOW+ (low density of CD5) NK cells in some patients with pulmonary tuberculosis. Unlike CD5-NK cells, most CD5LOW+NK cells had HLA-DR. We observed few CD5LOW+NK cells in the normal controls and some in the large granular lymphocyte (LGL) population purified by Percoll density centrifugation. Sorted CD5LOW+NK populations were LGL. The CD5LOW+NK cells had high lytic activity on K562 cells in a 4-h 51chromium release assay. Our results indicate that there is a previously unidentified subset of NK cells.