TCR gene expression in lymphoid and mucosal tissues of Xenopus laevis (VET1P.1122)

Abstract γδ T cells are a small subset of T cells that are considered to function as a bridge between innate and adaptive immunity. Because these cells are relatively few in number in most laboratory animals, except during the fetal period and in mucosal tissues, it is difficult to clearly delineate the functions of γδ T cells. In order to begin to characterize the γδ T cell populations in Xenopus laevis, previous work from this lab established a semi-quantitative RT-PCR method of analysis of TCR γ and TCR β gene expression in X. laevis thymus and spleen. We have extended these studies to evaluation of expression of TCR γ, β, α and δ transcripts in the thymus and spleen as well as the skin, intestine and lungs of young adult X. laevis. Based on evaluation of TCR transcript levels by RT-PCR, γδ T cells are likely to be abundant in the mucosal tissues evaluated, and the levels of TCR γ are higher in the X. laevis thymus and spleen than expected for adult humans or mice. We suggest that X. laevis is a γδ T cell “high” organism, perhaps related to the position of frogs as relatively early in the evolution of the adaptive immune response. Evaluation of expression of other T cell-related genes including the RAG genes and other genes involved in T cell development and function is ongoing. These results point to the use of X. laevis as a uniquely powerful laboratory animal model for studies of the evolution, development and function of γδ T cells.