Regulation of natural killer activity in vivo. III. Effect of hypophysectomy and growth hormone treatment on the natural killer activity of the mouse spleen cell population.

Spleen natural killer (NK) activity against YAC tumor cells was reduced in female C57BL/6J mice hypophysectomized at 3 weeks and sacrificed 4-8 weeks later. Proportions of null cells and of target binding cells in spleens from hypophysectomized and sham operated mice were significantly different. Administration of ovine growth hormone (GH) (100 microgram/day, i.p. for 10 days) resulted in a marked recovery of NK activity in hypophysectomized mice. NK activity by spleen cells from hypophysectomized or sham operated mice (with or without GH treatment) was mediated by non-T, non-B lymphocytes.