Cytotoxic activity in children with insulin-dependent diabetes mellitus

We determined the percentage of circulating natural killer (NK) cells, using the monoclonal antibodies anti-CD57 and anti-CD16, NK cytotoxic activity (lytic units/10(6)) and lymphokine-activated killer (LAK) activity in 25 IDDM patients aged 3-23 years, 12 with disease for < 1 year (Group I) and 13 with disease for > 3 years (Group II). Nine age-matched healthy subjects served as controls. The percentage of CD57+ cells was similar in IDDM patients and controls, while the percentage of CD16+ cells was lower in IDDM patients (P < 0.05) than in controls. NK cell cytotoxic activity was lower in IDDM patients than in controls (P < 0.01), in Group I and II compared with controls (P < 0.005). LAK activity was similar in IDDM patients and in controls. No correlation was found between NK cytotoxic activity and metabolic control, HLA typing, while a negative correlation was found between NK cytotoxic activity and insulin requirement (P < 0.05). The decreased NK cytotoxic activity observed in our patients, in particular in long-standing diabetics, with normal NK cell number, could be due to a qualitative defect of the NK cells, or to a deficient IL-2 and/or TNF-alpha production, or to a immunomodulatory or immunosuppressing effect of insulin.