ANTI-CANDIDIAL ACTIVITY OF NATURAL-KILLER (NK) AND LYMPHOKINE-ACTIVATED KILLER (LAK) LYMPHOCYTES IN-VITRO

The natural cytotoxic effects of peripheral blood lymphocytes (PBL) on Candida stellatoidea and several other Candida species were examined by a colony forming inhibition (CFI) assay. Peripheral blood mononucle ar cells (PBMC), were incubated with C. stellattoidea yeast cells. Aft er the incubation period the colony-forming ability of the yeast was s ignificantly reduced. In similar experiments, six different Candida sp ecies (C. albicans, C. krusei, C. stellatoidea, C. tropicalis, C. pseu dotropicalis, C. guillermondii) were used as target cells. There was n o statistically significant difference in the anticandidial activities of PBL against the Candida species used. It was demonstrated that a f raction of lymphocytes, natural killer cells (NK), had the major natur al anti-candidial activity by using anti-Leu M1 (CD 15) and anti-Leu 1 1b (CD 16) monoclonal antibodies (mAbs) plus complement (C'). It was o bserved that inhibition of colony-forming ability of C. stellatoidea w as significantly (78-96%) reduced when anti-leu 11b plus C' were used. In addition, the colony formation inhibition capacity of NK cells was increased by recombinant human interleukin-2 (rhIL-2) while anti-inte rferon-gamma (IFN-gamma) had no effect. Besides the fact that: NK cell s are among those responsible for natural immunity against Candida spe cies, this colony forming inhibition assay performed with C. stellatoi dea yeast cells as target and monocyte-depleted PBMC as effector cells , is a simple method to assess NK cell activity.