Impairment of Natural Killer Cell Activity in Indian

Indian kala-azar patients have normal numbers of peripheral blood NK cells but impaired functional activity due to decreased binding and lysis of target cells. This impairment of NK activity could not be corrected by exogenous recombinant human alpha or gamma interferon. However, recombinant human interleukin 2 was able to restore this activity by augmenting conjugate formation and lysis of target cells. Kala-azar (KA) is the visceral form of leishmaniasis and is caused by the intracellular parasite Leishmania donovani. Visceral leishmaniasis is associated with many immunolog-ical dysfunctions involving T cells. Natural killer (NK) cell activity has received little attention in human visceral leish-maniasis. NK cells are defined as the CD16+ CD3- subset of peripheral blood mononuclear cells (PBMC) which lyses tumor cells, virus-infected cells, and certain normal cells without presensitization (17). NK cell activity has been proposed as an important mechanism in control of tumor growth, in regulation of hematopoiesis, and in host defens