Although it is known that bats harbor load of bacteria and viruses without manifesting any apparent sign of the diseases, much is not known about their immune system and immune responsiveness. So, the present study aims at investigating the lymphoid organs of two common species of bats from Egypt Rousettus aegyptiacus and Taphozous nudiventris. The parameters studied were determination of lymphoid organs weights and total count of lymphocytes in different lymphoid organs, T and B lymphocytes blastogenesis in cultures, and the histological structure of the lymphoid organs. The results revealed that the mean lymphoid organs weights including thymus, spleen, peripheral lymph nodes (PLN) and mesenteric lymph nodes (MLN) of female R. aegyptiacus and T. nudiventris are higher than those of male R. aegyptiacus and T. nudiventris. The total number of mononuclear cells in the thymus, spleen, PLN, MLN and bone marrow (BM) of female R. aegyptiacus and T. nudiventris are also higher than those of male R. aegyptiacus and T. nudiventris. The T cell mitogen (Con A) and the B-cell mitogen (LPS) induce marked blastogenic responses in both genders of R. aegyptiacus and T. nudiventris. Histologically, the thymus gland is a lobulated organ enclosed in connective tissue capsule, each lobule consists of outer cortex and inner medulla, the cortex of each lobule contains numerous lymphocytes and macrophages, while the medulla contains fewer lymphocytes. The spleen is characterized by the presence of numerous aggregations of lymphatic nodules; these nodules constitute the white pulp, surrounding the lymphatic nodules is a diffuse meshwork that forms the red pulp. The PLN and MLN have the same structure; they consist of a cortex and medulla. The cortex contains lymphocytes that are aggregated into lymphatic nodules; in the medulla, the lymphocytes are arranged as irregular cords of lymphatic tissue while the medullary sinuses course between these cords.
Thymus, spleen, lymph nodes, bone marrow, mitogen, histology