Normal T cell selection occurs in CD205-deficient thymic microenvironments.

The thymus imparts a developmental imprint upon T cells, screening beneficial and self-tolerant T cell receptor (TCR) specificities. Cortical thymic epithelial cells (CTEC) present self-peptide self-MHC complexes to thymocytes, positively selecting those with functional TCRs. Importantly, CTEC generate diverse self-peptides through highly specific peptide processing. The array of peptides utilized for positive selection appears to play a key role in shaping TCR repertoire and influencing T cell functionality. Whilst self-peptide diversity influences T cell development, the precise source of proteins generating such self-peptide arrays remains unknown, the abundance of apoptotic thymocytes failing thymic selection may provide such a pool of self-proteins. In relation to this notion, whilst it has been previously demonstrated that CTEC expression of the endocytic receptor CD205 facilitates binding and uptake of apoptotic thymocytes, the possible role of CD205 during intrathymic T cell development has not been studied. Here, we directly address the role of CD205 in normal thymocyte development and selection. Through analysis of both polyclonal and monoclonal transgenic TCR T-cell development in the context of CD205 deficiency, we demonstrate that CD205 does not play an overt role in T cell development or selection.