Histological observation and innate immune barrier study of head kidney of Pelteobagrus vachelli

To investigate the histological structure and immune function of head kidney of Pelteobagrus vachelli, we used hematoxylin-eosin (HE) staining and modified James staining to observe its microscopic structure, and applied trypan blue vital staining to locate its immune barrier site. The results show that the head kidney of P. wallichii consisted of capsule, lymphoid zone, granulocytic zone, anterior interrenal tissue, reticular fibers and collagen fibers, and collagen fibers were only visible at the periphery of blood vessels. Trypan blue was mainly distributed in endothelial cells around sinusoids and some free melanin macrophages, showing an increasing trend with time. Results suggest that endothelial cells of red pulps and free macrophages form the innate immune barrier of head kidney.