Identification Of Zebrafish CD4~+ CD8~+ T Cell And It's Response To ISKNV Infection

Mammalian Th cells and Tc cells are defined by their expression of either the CD4 or the CD8 glycoproteins.With CD8 interact specifically with MHC class II,Tc cells can directly kill virusinfected cell;whereas CD4 interact specifically with MHC class II,Th cell cause inflammation and Humoral immune.Zebrafish CD4,CD8αand CD8βwere analyzed by using the bioinformatic software.They have conserved cysteine,and structure are similar to human.Based on bioinformatic result we select peptide with high antigenicity to prepare mouse antibodies of CD8αand CD8β,rabbite antibodies of CD4 , and then purified.Specificity of the antibodys were identified by indirect immunofluorescence (IFA) and western blotting.we have investigated Peripheral blood lymphocytes of zebrafish by using CD4/CD8a antibody IFA and CD4/CD8b antibody IFA respectively.Expression analysis demonstrated that zebrafish CD4+ cell can express CD8αand CD8β.Whereas expression of CD4 was observed only in CD8α-cells.We studied zebrafish CD4+CD8+T cell response by using two antibodys(CD4 and CD8a)IFA after ISKNV infection.CD4+Cd8+T cell proliferate vigorously in the first week of infection.The number of CD4+CD8+T cell is up to the peak by 8 days after infection,and then decreased after 10 days.These results suggested that CD4+CD8+T cell of zebra fish is similar to mammalian CD8+T cell,its response during acute infection can be broken down into three distinct phases:activation and expansion,contraction,and memory.Furthermore,increasing expression of CD4 is earlier than that of CD8,maybe CD4 assist the proliferation and activity of CD4+CD8+ T cells.This was the first time that CD4 and CD8 were identified to express on the same cell in fish.And we studied the function of CD4+CD8+ T cell,which help to know more about fish immune system and adaptive immunity.