Neonatal and adult recent thymic emigrants produce IL-8 and express complement receptors CR1 and CR2

22 Sep 2017

The maintenance of peripheral naïve T lymphocytes in humans is dependent on their homeostatic division, not continuing emigration from the thymus, which undergoes involution with age. However, post-thymic maintenance of naïve T cells is still poorly understood. Previously we reported that recent thymic emigrants (RTEs) are contained in CD31+ CD25− naïve T cells as defined by their levels of signal joint T-cell receptor rearrangement excision circles (sjTRECs). Here by differential gene expression analysis followed by protein expression and functional studies, we define that the naïve T cells having divided the least since thymic emigration express complement receptors (CR1 and CR2) known to bind complement C3b- and C3d-decorated microbial products and, following activation, produce IL-8 (CXCL8), a major chemoattractant for neutrophils in bacterial defense. We also observed IL-8-producing memory T cell subpopulation co-expressing CR1 and CR2 with a gene expression signature resembling that of RTEs. The functions of CR1 and CR2 on T cells remains to be determined but we note that CR2 is the receptor for Epstein Barr virus, which is a cause of T cell lymphomas and a candidate environmental factor in autoimmune disease.