Effect Of FADD Deficiency On T Cell Function In Mesenteric Lymph Nodes

Fas-associated death domain protein(FADD)is an adaptor molecular known to transmit apoptotic signal induced by death receptors.At present,the function of FADD in mediating the apoptotic signaling pathway has been widely studied,but the non-apoptotic function of FADD remains elusive.The aim of this paper is to study the effects of FADD on peripheral T cellIn the present study,we produced the Cre/loxP-mediated CD4+T cell-specific FADD knockout mice(CD4-FADD mice),and geneotyped them by PCR and western blot.The ratio of CD4+ or CD8+T cells in the thymus and lymph node of CD4+T cell-specific FADD knockout mice was examined by flow cytometry.To further explore the function of FADD in T cell immunity,we analyzed and compared the T cell subsets and activation status in lymph node between CD4+T cell-specific FADD knockout mice and control mice via enteritis model.Lymphocytes were isolated from mesenteric lymph nodes and co-treated with PMA(5 ?g/ml)?Ionomycin(500ng/ml)for 4 hours.The ratio of activated T cells expressing CD69,and the ratio of Th1 or Th2 subsets were analyzed by flow cytometry.First,we identified CD4-FADD mice by PCR.The results of western blotting showed that the protein level of FADD was significantly decreased in the thymus of CD4-FADD mice,and FADD was almost absent in peripheral lymph nodes of them.The size of thymus,the number of T cells in thymus and the subpopulations of T cells in thymus of CD4-FADD mice did not change,indicating that T cells in CD4-FADD mice developed normally.There was no significant difference in the ratio of CD4+T cell between the CD4-FADD mouse and its control.The control mice had slightly more CD8+T cells in lymph node than that of CD4-FADD mice.In the enteritis model,the inflammatory symptoms of CD4-FADD mice were lighter than the control mice.The ratio of CD4+T cell of WT mice decreased significantly while the ratio of CD8+T cell had no change.The ratio of CD4+T cell of CD4-FADD mice did not change while the ratio of CD8+T cell increased.The results indicated that FADD deficiency would affect the function of mesentery peripheral T cells in TNBS-induced enteritis model.We further demonstrated that the enteritis model resulted in a decrease in the naive T cells(Tn)but an increase in effector T cells(Te).The decrease of Tn in CD4-FADD mice was 13%,while the rate of WT mice was 29%.Finally,FADD knockout resulted in a decrease in the ratio of CD69+T cells in lymphocytes from CD4-FADD mice than WT mice after the stimulation with PMA/Ionomycin.At the same time,we found that Thl and Th2 differentiation was significantly inhibited in FADD KO mice,but no obvious change in the ratio of Th1/Th2 between lymphocytes from two mice was observed.In conclusion,we speculate that FADD deficiency has no obvious effect on the proliferation of CD4+T cells.However,it may block the activation and differentiation of mature T cells and affect their responses to inflammatory stimulation.We also examined the ratio of CD4+T cells expressing cytokines in spleen T cells This would help to further understand the effect of FADD deficiency on T cell function.