CHANGES IN BLOOD AND SPLEEN LYMPHOCYTE POPULATIONS FOLLOWING ANTIGEN CHALLENGE IN IMMATURE MALE CHICKENS

1. The effects of antigen (Ag) injection on the distribution of lympho cyte populations of Cornell K-strain male chickens were studied. 2. Tw o experiments were conducted. In the first, chickens were injected wit h Brucella abortus (BA), a purported T-independent antigen. In the sec ond, chickens were injected with sheep red blood cells (SRBC), a T-dep endent antigen. Peripheral blood lymphocytes (PBL) and spleen lymphocy tes isolated at 0, 3, 6, 9, 12 and 24 h following Ag injection were st ained with monoclonal antibodies (mAb) detecting B-lymphocytes, CD4(+) and CD8(+) cells. 3. B-lymphocytes in the blood or spleen showed no s ignificant changes following either BA or SRBC injection. In contrast, CD4(+) cells were decreased in the blood and increased in the spleen following BA and SRBC injections. CD8(+) cells were decreased in both blood and spleen following BA injection but were unchanged in either b lood or the spleen following SR8C injection. 4. These results indicate that there is a change in both spleen and circulating lymphocyte popu lations, especially T-helper cells, following Ag injection. T-helper c ells are apparently the primary population involved in the initiation of humoral immunity.