AGE-RELATED PATTERNS OF CHANGES IN THE SPLENIC WHITE PULP IN HETEROTYPIC STRESS: EXPERIMENTAL IMMUNOHISTOCHEMICAL STUDY

The effect of exposure to chronic heterotypic stress on the spleen was studied in Sprague-Dawley rats (n=48) of different age groups (infantile and peripuberal periods of ontogenesis) using immunohistochemical methods. Immunohistochemical reactions were performed on histological sections of the spleen using the antibodies against markers of lymphoid and dendritic cells, proliferation and apoptosis, with subsequent image analysis. The study demonstrated that in the infantile heterotypically stressed animals the morphometric parameters of populations of both T-(CD4+, CD8+, CD90+) and B-cells (CD20+) in the spleen were reduced more than in the peripuberal rats. In both age groups this reduction was more significant in heterotypic stress group compared to the homotypic stress-exposed animals. The number of the OX-62+ dendritic cells decreased only in the peripubertal rats exposed to stress, with insignificant differences between homo- and heterotypic stress groups, while the number of the follicular dendritic cells was reduced in both ages with significant differences between homo- and heterotypically stressed groups. Thus, heterotypic stress-induced immunomorphological changes in the spleen have different age-related pattern compared to those induced by the homotypic stress. This may be associated with diverse hypothalamo-hypophyseo-adrenal axis activation patterns in immature animals of various age groups exposed to different types of stress.

spleen, stress, early postnatal development, immunohistochemistry, image analysis