Immunohistochemical characterisation of lymphoid subpopulations and CD34+ cells in the lymphoid tissue of rabbit appendix
Objectives: The cecal appendix is present in 50 mammalian species, including the domestic rabbit. According to current data, it carries out many functions, the main of which is its role as a component of peripheral (secondary) organs of hemo and lymphopoiesis. In addition, some studies reported the appendix may function as an equivalent of the avian bursa of Fabricius and be a source for the development of B cells in mammals.
For the determination of the cecal appendix's exact functions as an organ of hemo and lymphopoiesis, immunohistochemical studies of its lymphoid tissue are necessary. They enable the identification of its cellular composition and analysis of its role in hematopoiesis. Therefore, the aim of our study was to establish the content and localization of hematopoietic stem cells and lymphoid subpopulations in the domestic rabbit cecal appendix.
Materials and Methods: Cecal appendix tissue samples were collected from four 4-months-old Pannon White male rabbits. For immunohistochemical studies, monoclonal antibodies CD3, CD10, CD20, and CD34 (DAKO, Denmark) were used.
Results: We found that lymphoid tissue of the rabbit appendix contains CD34+ cells. They are predominantly in the germinal centers of secondary lymphoid nodules and also appear in the domes of lymphoid nodules and diffuse lymphoid tissue. We found a few CD34+ cells in the walls of the crypts in the mucosa. CD20+ cells (B cells) predominated among the lymphoid subpopulations in the nodular form of lymphoid tissue. It also contained many CD10+ cells (precursors of T cells and B cells), which were mainly concentrated in the germinal centers of secondary lymphoid nodules. In the diffuse form of lymphoid tissue, the vast majority of cells expressed the CD3 marker (T cells).
Conclusions: The presence of CD34+ cells in the lymphoid tissue of the rabbit appendix may indicate hematopoietic stem cells.