Study On Basic Immunity Of The Bullhead Catfish, Pelteobagrus Fulvidraco

Three different isolating methods were applied to find the best way to purify serum IgM from the bullhesd catfish, Pelteobagnts fulvidraco in the present study. The purity and molecular weight of the serum IgM were determined, and then the rabbit polyclonal antisera were prepared with the purified IgM. In addition, the microstructure and ultrastructure of the peripheral blood cells and the thymus of the bullhead catfish were observed and described. All these results would benefit for the further study of the immunology of the bullhead catfish.In the purification of the serum IgM from the immunised and non-immunised fish, three kinds of affinity chromatographic column were used. They were mannan-binding protein (MBP) affinity chromatographic column, TG affinity chromatographic column and immunoaffinity chromatographic column. Among them, MBP affinity chromatographic column and immunoaffinity chromatographic column were effective to obtain abundant IgM with high purity, but the latter needed long immuised time. TG affinity chromatographic column was also an effective method for purifying but with low quantity of IgM outcome.By SDS-polyacrylamide gel electrophoresis (SDS-PAGE), the molecular weight of the IgM H chain and IgM L chain was determined, the value being 72.4kD and 29.9kD, respectively. Rabbit anti-bullhead catfish IgM polyclonal antisera were produced by immunizing rabbit with the purified IgM. Titre of the polyclonal antisera were measured by using sandwich ELISA. Total serum protein and the concentration of IgM of the normal sera of bullhead catfish were determined by using the Coomassie blue dye binding method of Bradford and sandwich ELISA, the values being 17.57mg/ml and 1.16mg/ml, respectively. The percentage of IgM in the total serum protein was 6.60% .On the stained peripheral blood smears of the bullhead catfish, seven types of blood cells were recognized. They were erythrocyte, thrombocyte, lymphocyte, monocyte. neutrophil, basophil and eosinophil. Moreover, the granulocytes could be classified into two types.The thymus of the bullhead catfish located at the back of the gill chamber, inside the opercular epithelium and outside the epioticopharyngoclavicularies. A well-developed thymus of the fish can be divided into three parts: the outer zone, middle zone and inner zone. The outer zone was made up of reticular cells, columnar cells and mucous cells; while the middle zone was characterized with larger number of deeply stained and compacted lymphocyte, In the middle and inner zones, there were several HassalFs corpuscles, which were made up of two or more endothelial cells surrounding an empty chamber or a mast cell. Some small holes on the thymus membrane could be obseryed, which might be responsible for the antigen ingestion. The thymus of 1-year-old fish was supported by connective trabecula, and that of 2-year-old fish showed apparently degenerating. The thymus of the 3-year-old fish just remained a specially degenerated structure.