Quantifying IFN-g and IL-10 Production During Graft Versus Host Response Following Treatment with TCDD

2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is a potent immunosuppressant and prototypic ligand for the aryl hydrocarbon receptor (AhR). It has been shown that suppression is primarily dependent upon AhR expression in the CD4⁺ T-cell. In a graft-versus-host (GvH) response, treatment with TCDD suppresses a cytotoxic T-lymphocytes (CTL) response by Day 10, concurrent with a T-regulatory like phenotype in the CD4⁺ T-cell, observed on Day 2. The phenotype in the CD4⁺ T-cell was characterized by expression of CD25, CTLA-4, and CD62L^low, and secretion of IL-10, an immunosuppressive cytokine. TCDD-mediated suppression may be due to the induction of this T-regulatory cell, which leads to altered cytokine production. In addition to IL-10, IFN-g also plays an important role in T cell differentiation. A review of pertinent literature shows that TCDD may alter the production of these two cytokines. Previous experiments have measured the effects of TCDD on cytokine production only on day 2 of a GvH response. We were therefore interested in seeing if changes in cytokine production persist through day 3, when the Treg phenotype is still evident. We tested supernatants from several prior GvH experiments to determine levels of these cytokines using enzyme-linked immunosorbent assays (ELISA). The results of these assays indicate no significant difference in IL-10 cytokine production between day 2 and day 3 and a significant difference in IFN-g in which cytokine production increased from day 2 to day 3. Identification of altered cytokine production following exposure to TCDD will provide addition insight to the TCDD-mediated immunosuppression seen in a GvH model.