Ultrastructural and functional changes of the mouse thymus following treatment with an antiserum specific for thymic epithelial cells

The effects of a rabbit antiserum (ATRES) specific for thymic epithelial cells (TREC) on the ultrastructure of thymus, on the serum levels of thymic factor(STF), and on the sensitivity of spleen rosette-forming cells to azathioprine were studied and compared in mice. Low and high doses of ATRES were employed. Following administration of ATRES, specific alterations of TREC but not of thymocytes and parallel decreases in STF and sensitivity to azathioprine were observed. These changes were more severe and of longer duration using high doses of ATRES. Complete morphologic recovery of TREC and normalization of STF levels and of sensitivity to azathioprine occurred simultaneously and earlier with low doses of ATRES than with high doses. The results of this study seem to indicate that a strict relationship exists between the morphologic state of TREC and STF production, since the integrity of the former seems necessary for a normal output of the latter, thus confirming that TREC are the site of STF production. The mechanisms by which ATRES affects TREC morphology, STF levels, and spleen cell sensitivity to azathioprine are discussed.