Anergy in vivo: down-regulation of antigen-specific CD4+ Th1 but not Th2 cytokine responses

Efficient immunologic tolerance, defined as antlgen-speclflcunresponslveness, can be peripherally induced by the l.v. Injectionof syngenelc splenocytes coupled with antigen using ethylenecarbodilmlde (ECDI). We have previously reported that unresponslvenessinduced via l.v. Injection of syngenelc splenocytes coupledwith intact, UV-lnactlvated Theiler's murine encephalomyelitisvirus (TMEV-SP) resulted in ‘split tolerance’. Bothvtrus-speclflc delayed-type hypersensltlvlty and lgG2a levelswere inhibited, whereas lgG1 levels were increased when comparedwith sham tolerized controls. In the present report we demonstratethat tolerance induced by l.v. Injection of TMEV-coupled splenocytesresulted in antigen-specific inhibition of T cell proliferation,as well as IL-2 and IFN- production in response to both wholeTMEV and the immunodomlnant viral epitope. Additionally, toleranceinduction resulted in abrogation of T_h1 -derived IL-2, IFN-and LT/tumor necrosis factor-ß (TNF-ß)]cytokine mRNA expression in response to In vitro stimulationwith UV-inactlvated TMEV as determined by reverse transcrlptasepolymerase chain reaction. In contrast, expression of T_h2-derived(IL-4, IL-6 and IL-10) cytokine mRNA was not affected in tolerizedmice. Tolerance functioned directly at the level of CD4⁺ T_h1cells at both the induction and effector limbs as depletionof CD8⁺ T cells both prior to in vivo tolerizatlon or in vitroculture had no effect on inhibition of T_h1-specific responses.The mechanism of In vivo tolerance induction appeared to beanergy of CD4⁺ T_h1 cells since IL-2, IFN- and LT/TNF-ßmRNA expression as well as virus-specific prollferatlve responsescould be restored by addition of rlL-2 to In vitro culturesof tolerant, CD4⁺ T_h1 populations. These results suggest thatin vivo ‘split tolerance’ Induced by l.v. Injectionof ECDI-flxed, antigen-coupled splenocytes involves anergy ofTMEV-speclflc, CD4⁺ T_h1 lymphocytes and concomitant primingof T_h2 cells. The induction of antlgen-speclflc, in vivo anergyhas important implications in the design of therapeutic strategiesfor immunopathologic diseases mediated by T_h1 lymphocytes, especiallyT cell-mediated autoimmune disorders.