Natural killer cell activity in patients with pulmonary tuberculosis and in healthy controls

Natural killer (NK) cell activity of freshly isolated peripheral blood mononuclear cells (MNC) or cells stimulated for 72 h with 10 micrograms/ml of a sonicate antigen of Mycobacterium tuberculosis H37Rv were studied in healthy responder and non-responder controls, as detected by lymphocyte proliferation with specific antigen, and in patients with pulmonary tuberculosis. K-652 cells were used as targets in a 4 h 51Cr release assay. MNC from patients exhibited a significant decrease in NK function as compared with responder controls (p less than 0.02). NK activity in responder individuals was highest 72 h after incubation with antigen. Non-stimulated cells were not cytotoxic. MNC from healthy responder and non-responder subjects incubated for 72 h with antigen yielded a significant increase in the percentage NK cytotoxicity at all effector/target ratios studied (p less than 0.01) as well as in the number of lytic units per culture (p less than 0.004). However, this increase was higher in responder individuals as compared to non-responder subjects (p = 0.02). The response to antigen was not significant in the group of patients although a net increase was also observed in the whole group. Only 4 of 9 patients exhibited significant increased responses after antigenic stimulation, 3 showed moderate responses, 1 did not respond and in a further patient a decrease was observed. The decreased NK activity could be secondary to abnormalities in the production of lymphokines by tuberculous patients. Although the role of non-specific cytotoxic cells in tuberculosis is unknown, their alterations could contribute to the pathogenesis of the disease.