コイ頭腎におけるリンパ球の分布と抗体産生細胞に関する免疫組織化学的研究 Distribution of lymphoid cells and immunohistochemical study on the antibody-producing cells in head kidney of carp (Cyprinus carpio L.)

博士論文

Morphological features in relation to immune response of head kidney, which was considered as major lymphatic organ in carp, were investigated by histological and immunohistochemical techniques. The results obtained in this study are as follows: 1.Number and distribution of lymphoid cells in carp organs considered as lymphatic tissue were histoplanimetrically examined. The number of lymphoid cells in head kidney was next to that of thymus and prominent lymphoid cell aggregations were found around blood vessels in the head kidney. The cellular density of the lymphoid cell aggregations around the blood vessels in head kidney was higher than in the thymus. These results were considered as one of morphological features in association with the immune response in head kidney, and also confirmed the in vitro results that the head kidney of carp was one of the major lymphatic tissues. 2. The morphology and distribution of immunocompetent cells were examin in relation to the architecture of vascular system in carp head kidney. Blood vessels in the head kidney were histologically identified into arteries, sinusoids, conventional veins and portal veins. The arrangement of the blood vessels in the carp head kidney was supposed to be similar to that in the liver of mammals, and might be favourable for trapping foreign materials. Lymphoid cell and pigment containing cell aggregations were exclusively found around the portal veins and the connection between the portal veins and sinusoids. 3. After alum-precipitated bovine serum albumin (AP-BSA) injection, AP-BSA bearing phagocytes and immunoglobulin (Ig) containing cells were immunohistochemically investigated. AP-BSA were initially phagocytosed in and around the sinusoids by macrophages, which gradually aggregated into the pigment containing cell clusters around the portal veins in head kidney. Pyroninophilic cell aggregations were also occurred adjacent to the pigment containing cell clusters in association with the appearance of the AP-BSA in the clusters, . Pyroninophilic cell aggregations consisted of lymphocytes, plasma cells and lymphoblasts in electronmicroscopy, and immunohistochemically immunoreactivity against carp Ig was detected in the rough endoplasmic reticulum of the plasma cells and the lymphoblasts. It is suggested that pyroninophilic cell clusters is areas for lymphocyte proliferations (probably B cell lineage) and might be primitive germinal centers in carp. In the parenchyma of head kidney, Ig containing cells (plasma cells) were increased after the AP-BSA injection, and their morphological changes and migrating features through endothelium were also observed. It is suggested that plasma cells differented in the head kidney migrate into the blood circulation or morphologically changed to produce Ig . Carp head kidney has been considered as a lympho-hematopoietic tissue. Although the parenchyma of head kidney is mainly granulopoietic tissue, aggregations of lymphoid cells and macrophages around the portal veins is phylogenetically sign of division between the lymphatic and the hematopoietic tissues. Morphological features after antigen treatment, such as occurrence of germinal center like structures , Ig producing cell increase and its morphological changes accompanied with the antigen aggregation, suggest that the areas around portal veins are important for immune response in carp head kidney.