Effect of androgens on the ontogeny of humoral immunity in chickens.

Steroids have significant influences on the immune system of birds and mammals, and the Food and Drug Administration should consider them in the regulatory review process. As discussed here, androgens have different effects depending on dose and the timing of administration. If given in sufficient amount during the critical time of bursal development, androgens may delay or permanently impair development of humoral immunity. If given after the bursa has developed, androgens apparently cause precocious migration without precocious maturation. Possibly, the cells fail to mature because of the absence of additional signals such as the immune modulating peptide hormones elaborated by reticuloepithelial cells of thymus and bursa. Even though the FDA requires that drugs for use in domesticated animals be tested in the species for which approval is being requested, chickens provide us with an inexpensive and useful experimental animal for preliminary studies of a drug's effect on the ontogeny of humoral and cellular immunity.