Plasma cell quantitation in the gland of Harder during infectious bursal disease virus infection of 3-week-old broiler chickens.

Histopathologic changes in the gland of Harder (GH) and bursa of Fabricius (BF) were studied during and after infection of 3-week-old broiler chickens with a pathogenic strain of infectious bursal disease virus (IBDV). Plasma cell (PC) necrosis in the GH was seen from 5 to 14 days postinoculation (PI), BF follicular necrosis was observed from 1 to 7 days PI. PC numbers within the GH, counted for 28 days after inoculation, declined and were reduced (P less than 0.01) by 51% at 7 days after inoculation, which coincided with PC necrosis and heterophil infiltration. After 14 days PI, however, PC numbers were equal to those in uninfected controls. Since the GH is a major antibody-producing site in the paraocular area, the reduction in PC number at 7 days PI might indicate compromise of local immunity in the paraocular region and upper respiratory tract associated with IBD.