Localization of thymostimulin in mammalian thymuses: comparative evaluation.

An anti-thymostimulin (TS) serum was tested on rabbit, guinea-pig, lamb and pig thymuses to study the localization of the hormonal factor. The immuno-peroxidase method, with some modifications, was applied to tissue fixed in Bouin's or in Bouin-PAF liquids and embedded in paraffin wax. Immuno-reactivity was shown in reticulo-epithelial cells in the cortex, in the medulla and in the external cells of the Hassall's corpuscles. The intensity of the immuno-reaction is stronger in pig thymus, whereas in lamb, rabbit and guinea-pig thymuses it is more uniform and pale, but to varying degrees. Comparison with the localization of TS in thymuses of other mammals and man and the problem of species-specificity were discussed.