Hormones and the immunological capacity. V. Modification of growth hormone-producing cells in the adenohypophysis of neonatally thymectomized germ-free mice: an electron microscopical study.

An electron microscopical study has been carried out to evaluate the effect of neonatal thymectomy on the hypophysis of germ-free mice at different times after the operation. The results fully confirm the previous findings in neonatally thymectomized, conventional mice. Also neonatal thymectomy in germ-free mice results in degranulation of growth hormone-producing cells in the anterior pituitary gland. A large number of these cells show an enlarged endoplasmic reticulum with formation of cisternae and loss of hormone granuli. This alteration of growth hormone-producing cells is similar to that observed in other cells of the hypophysis after removal of other target glands such as thyroid or gonads. The changes in the growth hormone-producing cells in neonatally thymectomized germ-free mice occur even in the first days after birth, when the number of differentiated growth hormone-producing cells is still very low. Some thymectomized germ-free mice showed symptoms of the wasting syndrome but the alterations in their hypophysis were not more pronounced than those observed in thymectomized germ-free but nonwasting mice. The data fit well our suggestion that the perinatal thymus is under hypophysial control and that immunological maturation depends on endocrine function.