NATURAL-KILLER-CELLS PARTICIPATE IN THE EARLY DEFENSE AGAINST LEISHMANIA-MAJOR INFECTION IN MICE

In this study the role of natural killer (NK) cells in the course of e xperimental Leishmania major infection was investigated. NK cells in g enetically resistant C57BL/6 mice were depleted by in vivo administrat ion of anti-asialo-GM1 or anti-NK1.1 antibodies. A marked exacerbation of the infection was found in the NK-depleted mice within the first t wo weeks of infection. Both the local tissue swelling and the number o f parasites in the lesions were significantly higher than in normal an imals. Lymph node cells taken from infected NK-depleted mice released less interferon-gamma (IFN-gamma) when cultured in vitro. As an altern ate approach we have used poly I:C treatment in order to activate NK c ell activity in vivo in BALB/c mice, which are genetically susceptible to L. major infection. Poly I:C treatment led to milder symptoms and to a significantly lower parasite burden in the early course of infect ion. Lymph node cells from infected and poly I:C-treated BALB/c mice r eleased higher amount of IFN-gamma in vitro than cells from control mi ce. These data show that NK cells are active participants in the non-s pecific phase of anti-leishmanial activity in the control of parasite multiplication early in the course of L. major infection in mice.