RESUMO
This experiment compared the histological characteristics and distribution of CD3 and CD79a among yak lymph nodes, hemal nodes and spleen. The three organs from ten clinically healthy newborn and adult yaks were studied using histology and immunohistochemistry. The yak hemal nodes, which consisted of blood sinuses, lymphoid follicles, diffuse lymphoid tissue and lymphoid cords, appeared to share the histological characteristics of the spleen and lymph nodes: the lymphoid follicles of the hemal nodes were much like those of the lymph nodes, which were not surrounded by the central artery and periarteriolar lymphoid sheath. The lymphoid cords of the hemal node, which contained many erythrocytes, were much like the splenic cords. The sinuses of the hemal nodes had a similar structure to the lymph sinuses of the lymph nodes but were engorged with erythrocytes rather than lymph as in the lymph nodes. Interestingly, the splenic sinuses of yak were of two different types: the sinuses with obvious endothelial cells or those consisting of reticular cells. The CD3+ cells were mainly located in the paracortex area and medulla of the lymph nodes, the diffuse lymphoid tissues of the hemal nodes, and the periarteriolar lymphoid sheaths and red pulp of the spleen. Most CD79a+ cells were mainly detected in the lymphoid follicles of all examined lymphoid organs. The results suggested that although the three organs had specific characteristics, in some respects, they had similar organizational structural characteristics and immune functions. These may be useful to better understand the relationship between the morphology and function of these organs and provide useful references for normal yak lymphoid organs.