军曹鱼黏膜免疫组织发育的形态学研究

Morphological studies on development of mucosal immune tissues in cobia Rachycentron canadum

运用组织学及组织化学的染色方法,对出膜后第l^44天(days post-hatch,dph)的军曹鱼(Rachycentron canadum)黏膜免疫组织的发育过程进行研究。结果显示,白细胞在黏膜免疫组织出现的时间顺序由早到晚依次为鳃、皮肤、胃、肠,同大量抗原接触鱼体组织时白细胞出现的时间顺序相符。军曹鱼胃固有层中丰富的白细胞说明胃可能在黏膜免疫中发挥着很大的作用。黏液细胞最早出现在胃;其后是皮肤和肠道;鳃最晚。在胃肠、皮肤内的黏液细胞几天后就可分泌中性至酸性黏液物质,且分泌量随鱼体分发育而增多,但在鳃组织内,黏液的分泌早于黏液细胞的出现。在采样的时间段里,黏膜免疫组织未发现浆细胞,可能是由于B细胞还没有发育成熟并具备免疫功能。从白细胞在军曹鱼黏膜组织内发育及分布的状况,可见黏膜组织具有完成免疫应答的细胞基础。

Methods of histology and histochemistry were applied to study the development of the mucosal immune tissues in cobia （Rachycentron canadum）, from the first to the 44th day post-hatchery （dph）. The results showed that the leucocytes appeared in mucosal immune tissues in the order of gill, skin, stomach and intestine. At 3rd dph, macrophage-like cells were first detected in the base of gill filament and lamella, and 3 days later, macrophages or lymphocytes appeared in the lamina propria of stomach and the epidermis dermis of skin. However, only a few lymphocytes were found in the lamina propria of intestines after 9th dph. When the fish were exposed to a great deal of antigen, the leucocytes appeared in the mucosal immune tissues followed the same time order as above. Abundant leucocytes distribution in gastric lamina propria suggested stomach play an important role in mucosal immunity just like intestines. The mucous cells were first observed in stomach at 6th dph, but they were not observed in skin and intestines until 8 days later, and the gill was the last mucosal immune tissues where mucous cells appeared. In addition, a large number of mucous cells like gland on the base of gill lamella were observed at 44th dph. It was proved by AB-PAS staining that mucous cells in stomach began to secrete mucus 3 days later than those cells appeared. Similarly, the mucus was secreted much later in skin and intestines. Unlike stomach, skin and intestines, the mucus had been secreted before the mucous cells appeared in gill lamell. The neutral or acidic mucus was detected on the base of gill lamell at 34th dph, but the mucous cells were not found then. The quantity of mucus increased gradually with the development of the fish. Plasma cells were not observed in mucosal immune tissues among the samples we collected. Although B lymphocytes were not mature, the mucosal tissues had possibly acquired immunity. It was suggested that the mucosal tissues possess the cell base of immune response according to the development of leucocytes distribution in them.