Assessment of CD4 expression by early T precursor cells and by dendritic cells in the human thymus
Sotzik, F.; Rosenberg, Y.; Boyd, A.W.; Honeyman, M.; Metcalf, D.; Scollay, R.; Wu, L.; Shortman, K.
Journal of Immunology 152(7): 3370-3377
1994
ISSN/ISBN: 0022-1767 PMID: 7511645 Document Number: 436247
The adult mouse thymus contains a minute population of early lymphoid precursor cells that express moderate levels of CD4. We searched for a corresponding population of early T precursors in the infant human thymus, by first depleting the majority of more mature thymocytes, then using immunofluorescence and flow cytometry to analyze cells bearing a range of early T lineage markers. No discrete population of early T precursors expressing CD4 was observed, in contrast to the murine thymus. Most putative very early human thymocytes were CD4-8-3-1-2-lo044+34+ 7-hi class I MHC-hi class II MHC-. However, a distinct population of human thymic dendritic cells expressing high levels of CD4 was isolated. These were CD4-hi8-3-1-2-44+34-7- class I MH Chi class II MHC-hi, and lacked markers of B cells, NK cells, or myeloid cells. They were large cells that exhibited dendritic morphology after brief periods of culture, and they were efficient stimulators of allogeneic T cells. The biologic implications of CD4 expression by thymic dendritic cells are discussed.