Absence of B stem cells in spleens of chickens fed the androgen analog mibolerone.

Bursa-derived stem cells in the spleens of chickens treated with the androgen analog mibolerone or with cyclophosphamide and in the spleens of untreated controls were examined by a transplantation technique. Spleen cells from syngeneic donors 2-20 weeks old were transferred to syngeneic cyclophosphamide-treated recipients, and the immunocompetence of the recipients was tested 5 weeks after the transfer by antigenic stimuli with sheep erythrocytes and Brucella abortus. Spleens of mibolerone-treated chickens failed to reconstitute the immunologic capability of cyclophosphamide-treated recipients in a manner similar to spleen cells from normal donors. Spleens of cyclophosphamide-treated donors did not contain stem cells. Stem cells were detected in the spleens of untreated controls as young as 2 weeks old; activity was highest after the 13th week of age.