ABSTRACT
Immunologists face a thought-provoking question in considering natural killer (NK) cells and disease. NK cells activity probably plays no role as a mediator of antigen-associated killing or lymphokine production in such infections as malaria or toxoplasmosis, or in skin disorders like psoriasis or pemphigus vulgaris. In chronic viral infections or autoimmune diseases of viral etiology, NK cells may play a role. Virus-transformed cells can induce Interferon and thereby elevate NK cell activity. Bacterial and parasitic infections cause an early increase in NK cell activity, but chronicity may depress it. In primary syphilis, NK cell activity is normal or elevated; in secondary, latent, and lipoidal Ab-positive syphilis it is reduced. NK cell activity in syphilis thus is activated by disease but is depressed by disease progression. In acute and chronic active hepatitis B virus infection, there have been several reports that acute hepatitis patients have normal NK cell activity and antibody-dependent cellular cytotoxicity.
