Antigenic Re-activation of Murine Th1 Lymphocytes Enhances their Capacity to Induce Ocular Inflammation, but Reduces their Expression of the Chemokine Receptor CXCR3

Abstract

Abstract: : Purpose: Chemokine receptors and their ligands are critical in the selective recruitment of effector T cells during inflammation. CXCR3 is a marker for activated and memory Th1 cells in both humans and mice and plays a major role in pathogenic processes mediated by these cells. Upregulation of CXCR3 and its ligands was previously found in mouse eyes developing Th1-mediated inflammation (Foxman et al., J Immunol, 2002, 168: 2483). The present study compared the expression of CXCR3 by Th1 cells, at various stages of activation in vitro, with the cells’ capacity to induce ocular inflammation. Methods: Naïve Th cells expressing TCR specific to hen egg lysozyme (HEL) were isolated, activated/polarized in vitro to Th1, expanded by IL-2 (to become "memory cells") and re-activated by HEL, as well as tested for their capacity to induce ocular inflammation in transgenic mice expressing HEL in their lens as detailed in Kim et al. (IOVS, 2002, 43:758). CXCR3 expression was determined on cells by flow cytometry and its mRNA expression was examined by RT-PCR. Results: Naive Th cells expressed little CXCR3 and did not induce ocular inflammation at the tested numbers. Activation, along with Th1 polarization of naive cells, increased profoundly both their CXCR3 expression and immunopathogenicity. Subsequent incubation with IL-2 further elevated the CXCR3 expression, but reduced the cells’ pathogenicity. Unexpectedly, re-activation of the memory Th1 cells reduced dramatically their CXCR3 expression, but augmented substantially their immunopathogenicity, to levels higher than those of primarily activated cells. The changes in CXCR3 levels on the Th1 cells were in accord with the levels of its mRNA transcript. Conclusions: These observations shed new light on the relationship between activation of Th1 lymphocytes, their expression of CXCR3 and their capacity to mediate inflammation. Of particular interest is the finding that re-activation of Th1 cells reduces their CXCR3 expression, but enhances their capacity to induce immune-mediated ocular inflammation.

Keywords: inflammation • flow cytometry • uveitis-clinical/animal model