Peculiarities of lymphocytes emigration from newborn thymus
Keywords:thymus, lymphocytes, lymphatic vessels, mast cells
Introduction. Mechanisms of mass lymphocytes’ emigration from thymus are still unclear. The process of lymphocytes migration and mechanisms, which provide it, form one of the important problems of immunomorphology.
Aim of the work: to establish the peculiarities of newborn thymus structure and to reveal pathways and mechanisms which provide lymphocytes’ emigration from thymus.
Materials and methods. Morphological, histological and histochemical analyses of 160 rats’ thymuses from birth up to the 7th day after birth were conducted and discussed. The animals were handled according to the European Commission Directive (86/609/EEC). The profound microscopic analysis of cell contents, lymphatic vessels morphology in morpho-functional areas of rats’ thymuses during the first week after birth in 4 hours interval was carried out. All quantitative results were estimated by the statistic methods.
Results. It is settled that thymus specific density tightly depends on the quantity of degranulated mast cells, absolute quantity of microcirculatory vessels, especially of lymphatic ones. The index of specific density, lymphocyte-epithelial index change wavy during the first week after birth every 12 hours. These changes are followed by the changes of extracellular matrix structure, absolute quantity of small lymphocytes in thymic cortex and lymphocytes’ adhesive properties. The key periods are: from 0 till 2, from 12 till 16, and from 108 till 120 hours after birth. At that time discrete migration of lymphocytes from the thymus occurs through paravasal lymphatic vessels. After temporal edema reduction, lymphatic vessels turn to be empty, their quantity decreases.
Conclusion. Therefore, emigration of lymphocytes from thymus takes place through lymphatic vessels on the top of periodical short-term local edema.
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