CD83 expression influences CD4+ T cell development in the thymus

T lymphocyte selection and lineage commitment in the thymus requires multiple signals. Herein, CD4(+) T cell generation required engagement of CD83, a surface molecule expressed by thymic epithelial and dendritic cells. CD83-deficient (CD83(-/-)) mice had a specific block in CD4(+) single-positive thymocyte development without increased CD4(+)CD8(+) double- or CD8(+) single-positive thymocytes. This resulted in a selective 75%-90% reduction in peripheral CD4(+) T cells, predominantly within the naive subset. Wild-type thymocytes and bone marrow stem cells failed to differentiate into mature CD4(+) T cells when transferred into CD83(-/-) mice, while CD83(-/-) thymocytes and stem cells developed normally in wild-type mice. Thereby, CD83 expression represents an additional regulatory component for CD4(+) T cell development in the thymus.