Decreased natural and antibody-dependent cellular cytotoxic activities in intravenous drug abusers.

Peripheral blood lymphocytes from 14 adult male patients admitted to the hospital with complications of intravenous drug abuse (IDA) were examined for natural killer (NK) and antibody-dependent cellular cytotoxic (ADCC) activities, lectin-dependent cellular cytotoxicity, and interferon (IFN)- and interleukin 2 (IL-2)-induced NK activity. Serum was also assayed for circulating interferon levels and soluble factor(s) capable of suppressing the cytotoxic potential of allogeneic lymphocytes from healthy donors. IDA patients demonstrated significantly decreased levels of NK and ADCC activities compared to age- and sex-matched healthy controls. The lectin, phytohemagglutinin, could significantly enhance the cytotoxicity of IDA lymphocytes; however, activity was not completely restored to normal levels. IDA sera demonstrated a significant inhibitory effect on the NK and ADCC activities of normal allogeneic lymphocytes, and these sera contained negligible levels of circulating IFN. Although the NK activity of IDA lymphocytes could not be restored completely to normal levels by either IFN-alpha or IL-2, the percentage enhancement of cytotoxicity was remarkably higher in IDA patients with significantly reduced NK activity than that observed using PBL from patients with near normal NK activity. The ability of IFN or IL-2 to enhance the decreased cytotoxicity of PBL from drug abusers suggests a novel therapeutic approach to the management of the complications of IDA.