Distribution of anti-keratins and anti-thymostimulin antibodies in normal and in Down's syndrome human thymuses.

The localization of three monoclonal (A,B,C) anti-cytokeratin antibodies and of an anti-thymostimulin antibody were studied in normal children's thymuses, aged from 2 months to 10 1/2 years and in Down's children thymuses, aged from 5 months to 6 1/2 years. Two anti-cytokeratins were positive in the thymus: the anti-B was found in the epithelial cells of all thymic zones, the anti-C only in the external cells of Hassall's corpuscles. The distribution and the intensity of immuno-reactions were the same in normal and in Down's thymuses. The distribution of anti-thymostimulin was superimposed to the distribution of anti-cytokeratin B and was similar in normal and in the youngest Down's thymuses, whereas in the 6 1/2 years-old Down's thymuses there was a loss of anti-TS reaction in the subcapsular zone. A relationship between the reduction of anti-thymostimulin immuno-reaction and the beginning of an eventual loss of T-lymphocyte differentiation was supposed.