Effects of hypophysectomy on DNCB-induced contact sensitivity in rats

Cell-mediated immunity in hypophysectomized (HYX) and non-hypophysectomized (NHYX) rats was assessed by measuring lymph node weight and lymph node cellular proliferation responses to cutaneous application of the skin sensitizer dinitrochlorobenzene (DNCB). Differences were found in the lymph node weight assay, with the responses of the HYX rats being significantly lower than the responses of the NHYX rats. There were, however, no significant differences as measured by the lymph node cellular proliferation assay. An explanation for these contradictory results was sought by examining dose-responsiveness to DNCB. It was found that, over a range of doses of DNCB, HYX rats showed a linear dose-response relationship in terms of both lymph node weight and lymph node cellular proliferation. No dose-responsiveness was observed in NHYX rats. Since HYX rats required a greater degree of antigenic stimulation to achieve a response level equivalent to that of NHYX rats, it may be concluded that HYX rats are immunodeficient at lower antigen levels.