Specific B lymphocyte suppression by infectious bursal agent (Gumboro disease virus) in chickens.

Chickens infected experimentally with infectious bursal agent (IBA) during embryonation or early after hatching show a severe depression of bursa-dependent lymphoid components, and associated immune functions. Data presented here and elsewhere show that the degree of B cell suppression correlates with the time of infection. This would be compatible with a virus-induced block in B lymphocyte differentiation. Accordingly, the virus may be cytopathic for early (bursal) but not late (circulating) B lymphocytes or, more likely, the virus inactivates those non-lymphoid bursal cells mediating lymphocyte differentiation.