Spectrin localizations in the chicken bursa of Fabricius at different stages of development

Before and after hatching, light microscopic and ultrastructural observations of spectrin were performed immunohistochemically in the chicken bursa of Fabricius. Before hatching, the frequency of spectrin-positive cells was very low. Among the spectrin-positive cells spectrin was mostly detected in patchy or diffuse form in the cytoplasm and rarely seen at surface membranes. Although cortical lymphocytes were spectrin-negative, numerous medullary lymphocytes were spectrin-positive after hatching. In the medullary spectrin-positive cells, staining intensity was uniform. Spectrins showed ultrastructural heterogeneity after hatching. Although a new type of spectrin localization associated with surface membranes was observed, this type of spectrin localization was not prominent. The increased number of spectrin-positive cells, uniform staining intensity and the localization of spectrin associated with surface membranes seem to coincide with B cell differentiation.