Detection and localization of autofluorescent substances in thymus tissue of sheep

An oxygenated sterol was detected by chemical analysis of sheep thymus lipid extracts. It was characterized as 7 beta-hydroxycholesterol, which is well known for its biological activity. Using fluorescence microscopy, attempts were made to correlate this substance to particular histological structures of the thymus tissue. Microscopy revealed an intense yellow-green primary fluorescence distributed throughout the entire thymic parenchyma, which was predominant in the cortico-medullary junction, the vicinity of the Hassall's bodies and the subcapsular space. This indicated an accumulation of the fluorogenic substance in special tissue structures of sheep thymus. This result can be assumed as specific for the thymus, since such primary fluorescence was absent from other simultaneously investigated organs, such as the adrenal.