Activation of Natural Cytotoxic Activity In Vitro with Lymphocytes from Patients with Multiple Sclerosis

Natural killer (NK) cells are defined as lymphocytes with the capacity to lyse certain tumor cells and virus-infected cells without prior immunization (Herbermann and Holden, 1978). These cells constitute a heterogeneous subset of the lymphoid cell population. It has been demonstrated that interferon (IFN) plays an important role in the regulation of NK activity (Ortaldo et al., 1983). Recently, it has been demonstrated that interleukin-2 (Il-2) can also enhance NK cell activity (Grimm et al., 1983; Devos et al., 1984). Furthermore Il-2 has an important role in the regulation of IFNγ production (Kawase et al., 1983). This was confirmed with pure recombinant Il-2 by Svedersky et al., 1984 and by ourselves. Although the role of the endogenously produced IFNγ in the augmentation of NK activity by Il-2 has been a controversial issue, there is increasing evidence that the enhancement of NK activity by Il-2 is only partly mediated by IFNγ (Svedersky et al., 1984; Braakman et al., manuscript in preparation). Although the precise mechanisms by which NK activity are regulated remain to be established it is attractive to hypothesize that NK cells play a significant role in the natural resistance against virus infections. Among the immunoregulatory abnormalities in MS patients it has been reported that NK activity is decreased (Benczur et al., 1980; Hauser et al., 1981; Uchida et al., 1982, and Neighbour et al., 1982) and that IFN production is impaired (Neighbour and Bloom, 1979, and Benczur et al., 1980).