Suppression of murine allergic contact dermatitis by CTLA4Ig. Tolerance induction of Th2 responses requires additional blockade of CD40-ligand.

Blockade of costimulation through the B7-CD28 pathway by CTLA4Ig can lead to Ag-specific T cell tolerance. Most models studied to date involve a Th1-dependent response. To investigate whether the tolerizing effects of CTLA4Ig might vary depending upon the cytokine nature of the immune response, we studied its effects on contact hypersensitivity (CHS) in response to two allergens. In BALB/c mice, both 2,4-dinitrofluorobenzene (DNFB) and FITC induce CHS. However, the DNFB response is Th1-predominant, while the FITC response is Th2 predominant. CTLA4Ig treatment during primary sensitization induced long-lasting unresponsiveness to DNFB, with 88% and 76% inhibition of primary (first challenge) and secondary (re-sensitization and re-challenge) CHS, respectively. In contrast, CTLA4Ig inhibited primary CHS to FITC by over 82% but had little effect on secondary CHS. Consistent with its effects on CHS, the suppressive effect of CTLA4Ig on Th2 cells was short-lived in FITC-sensitized mice, while Th1-like cytokine-secreting cells remained reduced in DNFB-sensitized mice, even when the animals were rechallenged with DNFB. The addition of anti-CD40L Ab to CTLA4Ig was able to induce long-lasting unresponsiveness to FITC, indicating the ability of cells mounting this Th2 response to receive costimulatory signals through either pathway. In conclusion, CHS can be mediated by both Th1 and Th2 cells, and the ability of CTLA4Ig to lead to long-standing nonresponsiveness in this model depends on the nature (i.e., cytokine profile) of the immune response.