Immune deviation of 2C transgenic intraepithelial lymphocytes in antigen-bearing hosts

The present study examined self-tolerance for T cell receptor (TCR)alpha beta intestinal intraepithelial lymphocytes (iIELs) using the 2C transgenic (Tg) mouse model specific for a peptide antigen (Ag) presented by the class I major histocompatibility complex H-2L(d). Although Tg(+) T cells were largely deleted from the periphery of Ag+ mice, equivalent numbers of Tg iIELs were present in Ag+ compared to Ag- mice. Tg iIELs in Ag- mice contained CD8 alpha beta, CD8 alpha alpha, and CD4(-)CD8(-) subsets, whereas only CD8 alpha alpha and CD4(-)CD8(-) Tg iIEL subsets were detected in Ag mice. Analysis of surface markers revealed that Tg iIELs in Ag+ mice expressed decreased levels of Thy-1 and increased CD45R/B220 as compared to Ag- Tg iIELs. In response to activation with exogenous peptide or immobilized anti-TCR mAb, iIELs from Ag- mice proliferated at high levels and produced interleukin (IL)-2 and interferon (IFN)-gamma, while Tg(+) iIELs from Ag+ mice proliferated at low levels and failed to produce detectable IL-2 or IFN-gamma. Activation of sorted iIEL subsets from Ag- mice revealed that CD8 alpha alpha and CD4(-)CD8(-) subsets produced low levels of IL-2 and IFN-gamma in response to activation with antigen-presenting cells and added peptide or immobilized anti-TCR mAb, while CD8 alpha beta(+) iIELs responded to endogenous levels of peptide. In response to APC and exogenous peptide, sorted iIEL subsets from Ag+ mice produced IL-2 and IFN-gamma, and proliferated at greatly reduced levels compared to corresponding subsets from Ag- mice. Analysis of cytokine mRNA levels revealed that activation in vitro induced IL-2 mRNA only in Ag-, but not Ag+ iIELs, whereas a high level of IL-4 mRNA induction was detected in Tg(+) iIELs from Ag+ mice, and to a lesser degree, from Ag- mice. These data suggest that tolerance for Tg(+) iIELs resulted in the deletion of CD8 alpha beta(+) subsets and the persistence of Tg(+) iIEL subsets with decreased sensitivity to endogenous levels of self-peptide. A comparison of the cytokine profiles expressed by Tg(+) iIEL subsets in Ag- and Ag+ mice suggested that tolerance induction had involved the functional deviation of cells from TC1 (T helper-1-like) to a less inflammatory TC2 (T helper-2-like) phenotype capable of mediating humoral immune responses in the mucosa.