PHYLOGENETIC STUDIES ON IMMUNE RESPONSE .3. AUTORADIOGRAPHIC STUDIES ON LYMPHOID SYSTEM OF AUSTRALIAN ECHIDNA TACHYGLOSSUS ACULEATUS

  • 1 January 1967
    • journal article
    • research article
    • Vol. 13  (4) , 339-+
Abstract
In the Australian echidna Tachyglossus aculeatus, a close relative of the extinct ancestors of higher mammals, the lymphoid organs were investigated by means of autoradiographic studies after the injection of H3-thymidine and I125-labelled flagellar antigen of Salmonella adelaide. The histology of organs from echidnas injected with colloidal carbon was studied in parallel. Each lymph nodule in the echidna represents a single lymphoid follicle comparable to a cortical follicle in lymph nodes of higher mammals. Studies on lymph nodules of echidnas injected with H3-thymidine revealed the presence of highly active germinal centers, usually one per nodule. Antigen became localized first around the entire nodule; later on it was found within the germinal center or in its peripheral parts. Often a germinal center was eccentrically located, in which case the labelled antigen formed the typical germinal center cap known to be characteristic of secondary follicles in the rat lymph node. A significant uptake of antigen was also seen in the appendix, the Peyer''s patches of the gut and in the Hassall''s corpuscles of the thymus. Findings for the echidna lymph nodule are discussed with respect to their possible significance in the evolutionary development of the multi-follicular lymph node of higher mammals.