B-CELLS AND T-LYMPHOCYTE SUBSETS OF THE HEAD-ASSOCIATED LYMPHOID-TISSUES OF THE CHICKEN

The head-associated lymphoid tissues of the chicken, composed of the h arderian gland and the conjunctiva-associated lymphoid tissue (CALT), were studied to determine whether changes occurred in lymphocyte subpo pulations as chickens age from 1 week to 8 weeks. The B cells and subp opulations of T-lymphocytes of the head-associated lymphoid tissues we re identified using in situ immunohistochemical staining. Monoclonal a ntibodies specific for various lymphocyte surface antigens were used. The concentration of T-lymphocytes, particularly CD3(+) and CD4(+) cel ls, within the harderian gland increased with age, whereas the concent ration of B cells remained the same. B-lymphocytes were observed withi n the germinal centers of the CALT of 4-week-old birds. The T-lymphocy tes within the CALT surrounded the B-cell-rich germinal centers. CD3() T-lymphocytes were the predominant cell population in all age groups examined. Increasing concentrations of CD3(+), CD4(+), and CD8(+) T-l ymphocytes mere observed within the CALT as chicks developed from 1 we ek to 4 weeks of age. Finally, no changes were observed in lymphocyte populations within the CALT as chicks developed from 4 weeks to 8 week s of age.