Immunological Memory And In Vitro Proliferation Responses Of Lymphocytes Of Tilapia (Oreochromis Niloticus)

The distribution of special ASCs in head kidney, peripheral blood and spleen weremeasured by ELIPOT and the antibody level of fish serum was detected by the ELISA afterprimary and secondary immunization of Tilapia with Human IgG by intraperitoneal injection.In experimental groups, the special ASC were observed on1st day in head kidney afterprimary immunization and the peak of ASC was observed on12thday in headkidney,peripheral blood and spleen; the number of ASCs in head kidney was significantlyhigher than those of the peripheral blood and spleen, and the number of ASC of allexperimental groups were markedly higher than those of the controls’. Compare with theprimary immunization, more ASC were detected in the secondary responses of the headkidney,peripheral blood and spleen, the ASC peak of the secondary response appeared3daysearlier than primary immunization, The head kidney produced the highest number of ASC ofthe tested organs,the peak of ASC in head kidney was2times more than the primaryimmunization;higher level of serum antibody was observed in the secondary immunization byELISA assay.These data suggests that the memory formation had occurred.The head kidneywas the most important immune organ of the fish.The lymphocytes from head kidney,spleen and peripheral blood of Tilapia inexperimental groups were incubated with hunman IgG in vitro,also the control groups, andthe proliferation response was detected by MTT. The proliferation of peripheral bloodlymphocytes showed significantly higher response than the proliferation of lymphocytes ofhead kidney and spleen, especially, none or tiny significant reaction were detected in spleenlymphocytes, ELISPOT technology was used to detect the ASCs in three differentorgans:without the antigen Human IgG, the ASCs of head kidney survived at lease7days, theASCs of peripheral blood and spleen were disappeared on7thday, the life span of ASC ofhead kidney was longer than the other two organs’, indicating that the ASCs of head kidneywere long-lived plasma cells(LPC), the ASCs of peripheral blood and spleen were short-livedplasma(SPC); with the antigen human IgG, none significant proliferation response of ASCwere detected in three organs, on the contrary, the numbers of ASC of head kidney, peripheralblood and spleen were reduce rapidly，and the levels of antibody in the culture medium oflymphocytes of head kidney, peripheral blood and spleen were lower than the situation of without the antigen human IgG, indicating that the lymphocytes couldn’t be stimulatedeffectively by specific soluble protein in vitro; when stimulated with the non-specific antigenLPS, significant proliferative response of ASCs were detected in the lymphocytes of headkidney, peripheral blood and spleen,the proliferation of ASC of lymphocytes of peripheralblood was the most significant(P＜0.05), indicating that high proportion of plasmablasts wereexist in the peripheral blood of fish.In this study, the specific immune response of tilapia had been detected after the primaryand secondary immunization, followed by testing the proliferation and transformation oflymphocytes which were induced by specific and non-specific antigens in vitro.These dataprovided theoretic base for the research and development of humoral immunity memory andimmunology of fish.