APPEARANCE OF T-CELLS IN THE BURSA OF FABRICIUS AND CECAL TONSILS DURING THE ACUTE-PHASE OF INFECTIOUS BURSAL DISEASE VIRUS-INFECTION IN CHICKENS

Groups of 3-wk-old specific-pathogen-free chickens were inoculated int raocularly with two virulent and, one vaccine strain of infectious bur sal disease virus (IBDV). During the acute phase of infection, the bur sa of Fabricius and cecal tonsil were examined by immunohistochemistry for IBDV antigen and T cell. With all three viruses examined, the inf ection resulted in the appearance of viral antigen in the bursa accomp anied by tile presence of CD3+ cells. The CD3+ cells were predominantl y TCR2+ and appeared at the site where viral antigens were present. Th e CD3+ cells continued to persist in the bursa after most of the IgMcells and IBDV antigen-positive cells had disappeared. Similar appeara nce of CD3+ cells was noted following viral antigen accumulation in th e germinal centers of cecal tonsils in virulent IBDV-infected chickens . These results demonstrated that infection with IBDV resulted in exte nsive viral replication in the bursa and the cecal tonsils with an ass ociated accumulation of T cells, The role these T cells may play in ti le pathogenesis of IBDV infection remains to be established.