Abstract
By selective labeling of juvenile chicken bursal cells with colloidal fluorescein isothiocyanate in situ, the emigration rate of bursal lymphocytes to the periphery was estimated at approximately 0.84% and 0.96% of the peripheral blood lymphocyte (PBL) and splenic B cell pool per hour, respectively. Emigrant bursal cells were found primarily in blood and spleen, with very small numbers migrating to thymus, bone marrow, and gutβassociated lymphoid tissues. Emigrant bursal cells expressed high levels of both major histocompatibility complex class II antigen and the Ov alloantigen, a phenotype found on a population comprising approximately 4% of bursal cells from which the bursal emigrants may be derived. Surgical bursectomy at 3 weeks of age revealed that peripheral blood B cells could be divided into three distinct populations. Specifically, 60% of the peripheral blood B cells were short lived with a halfβlife of about 30 h in the blood. These cells accounted for the great majority of emigrants from the bursa to the peripheral blood. Approximately 35 % of PBL B cells had a halfβlife of 12 days following bursectomy and comprised cells which did not divide in the periphery. Consequently, we propose that physiological differences between this population and the majority of bursal emigrants are established intrabursally. The remaining PBL B cells, whose relative proportion increases with age from about 5 % of PBL B cells at 2β3 weeks of age, are short lived and are being continually produced from (a) postβbursal site(s) of B cell production.