Hypothalamic-immune interactions: neuromodulation of natural killer activity by lesioning of the anterior hypothalamus.

Placement of bilateral electrolytic lesions in the preoptic-anterior hypothalamic area (AHT) of Fischer 344 rats results in decreased splenic NK activity as compared to control and normal animals. Animals with AHT lesions have a decrease in NK activity 4 and 7 days after lesion placement, with a return to normal activity by day 14. Fractionation of spleen cells on glass bead columns results in nonadherent and adherent cell fractions with NK activity. AHT lesions affect NK activity only in the adherent cell fraction. The removal of macrophages from this cell fraction did not restore NK activity. Moreover, this NK activity is not the result of cytotoxic macrophages. Hypophysectomy decreases NK activity in lesioned and non-lesioned animals, suggesting the influence of pituitary factors. These data indicate that the anterior hypothalamus is capable of modulating the cytotoxic activity of NK cells. Thus, neuroimmunomodulation may be a potential factor in susceptibility to some disease states such as viral infections and neoplasia.