EFFECTS OF GONADAL-STEROIDS AND THEIR ANTAGONISTS ON THE HUMORAL IMMUNE-RESPONSE OF IMMUNE-SELECTED BROILER CHICKS

The effects of gonadal hormones, testosterone (Te) and estrogen (E(2)) as factors in the development of the immune system in two lines, high response (HC) and low response (LC), of broiler chickens divergently selected for early or late immune maturation were studied. For this pu rpose, plasma Te and E(2) levels were tested and correlated with immun e response. Also, the effects of exogenous administration of gonadal s teroids testosterone propionate (TP), dihydrotestosterone (DHT), and e stradiol S-benzoate (EB), and the nonsteroidal androgen antagonist flu tomide (Flu) and anti-estrogen tamoxifen (Tam) on the immune system we re studied. Male chicks of the LC line had a higher level of endogenou s Te during first 30 d posthatch. The administration of TP or DHT had no noticeable effect on the humoral immune response, whereas DHT suppr essed growth of the bursa of Fabricius of both sexes of HC line. No di fferences in the endogenous E(2) level were observed between sexes in either line. Administration of EB inhibited comb and testicle growth a nd enhanced significantly the humoral immune response to Escherichia c oli and sheep erythrocytes (SRBC). The anti-androgen Flu and anti-estr ogen Tam strongly inhibited humoral immune response to E. coli and SRB C antigen, whereas no effects on comb and testicle growth were observe d. The experimental results suggest that gonadal hormones have similar principal posthatch effects in avian as in mammals; however, the gona dal steroids prehatch effects and the genetic-physiological-environmen tal effects require further study.