Ultrastructure of apoptotic T lymphocytes and thymic epithelial cells in early postnatal pig thymus

The thymus is a primary lymphoid organ that provides the microenvironment required for the development of T lymphocytes. Thymic epithelial cells (TECs) are among the most critical components in the thymic microenvironment supporting thymocyte selection and maturation. Apoptosis is primarily a physiologic process that plays a major role during the development of T lymphocytes. The first purpose of this study was to examine morphological changes in apoptotic thymocytes by transmission electron microscope in piglets. The second purpose was to reveal the morphological typology of TECs in piglets. Tissue samples of the thymus were taken from healthy Yorkshire race pigs of two different age groups (7 days and 1 month). Ultrastructurally, apoptotic lymphocytes showed similar morphologies, but they also had differences in distribution. In both groups a high density of apoptotic and proliferating thymocytes was found in the cortex. The rate of apoptotic thymocytes in the cortex and medulla increased with age, respectively. It was observed that the TECs had various morphological subtypes in both the cortex and the medulla. A similar cellular distribution pattern of TECs was seen in both groups. It was concluded that the morphological diversity in the TECs may be related to the form-function relationship and the metabolic process.

Keywords:

Pig, ultrastructure, thymus T lymphocyte, thymic epithelial cells,

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