Analysis of humoral immune response of animals exposed to bacterial antigens

From the Aeromonas hydrophila strain, five different types of antigens such as heat killed antigen, whole cell antigen, heat killed antigen with antiserum, whole cell antigen with antiserum and nucleotide antigens were prepared and injected into the experimental fish (Catla catla) groups for the study of immunomodulation. Analysis of immunogenicity of antigens against the fish Catla catla was estimated. The A. hydrophila produced β hemolytic pattern on the blood agar plate. B lymphocyte counts using rosette forming assay revealed a significant decrement in pathogens exposed fishes as compared to controls. Fishes exposed to pathogenic strains (1/10(th) sublethal concentration) for 3 weeks showed a reduction in PFC. The effect or pathogenic antigens in direct spleenic plaque forming cells (1 g M producing cells) showed a reduction in the secondary plaque forming cell in the first 3 weeks and a time- and dose-dependent decrease in primary and secondary PFC response. A remarkable observation enhancement in B cell production due to immune complex of antigens was noted in the present study. The enhancement of this type of immune responses confirms the potential of immune complexes to be used as vaccines.