Abstract

During the maturation stages of thymocytes, apoptosis plays a crucial role for the production of immunocompetent T cells. On the other hand, changes of glycosylation may influence both T cell signaling and T cell development. Carbohydrate molecules are not only energy sources of the cells, but they can also responsible for the recognition phenomena such as protein targeting and cell to cell interactions. Therefore, glycosylation of cell surface proteins or lipids controls critical T cell processes, such as T cell death. Sialic acids, terminal sugar of the glycan motifs, are primarily responsible for the cellular interactions. In the present study, we purposed to determine of the cell surface carbohydrate alterations and the possible relationships of apoptosis with these alterations in the thymocytes from different periods of embryonic and newborn thymic tissues. Our terminal deoxynucleotidyltransferase-mediated dUTP nick end labeling (TUNEL) staining indicated that the thymocyte apoptosis is increased after the day 16of embryonic development and it proceeds in neonatal period. In addition, the surface density of sialic acids were decreased in newborn thymi when compared to embryonic tissues. These results indicated that, there is a significant relationship between cell surface sialic intensities and apoptosis. Thus, in the embryonic development, pathways which responsible for the thymocyte apoptosis may different from those of the newborn period due to masking effects of sialic acids. However, after the birth, sialic acid intensities were highly diminished in the thymocytes and, therefore they may undergo to apoptosis by another pathway(s), such as galactin-1 induced pathway.