CD34-POSITIVE EARLY HUMAN THYMOCYTES - T-CELL RECEPTOR AND CYTOKINE RECEPTOR GENE-EXPRESSION

CD34, a stem cell marker, has been shown to be expressed on human CD3( -)CD4(-)CD8(-) (triple-negative; TN) thymocytes. Phenotypic and functi onal analyses suggest the following differentiation sequence: CD34(+)1 (-)3(-)4(-)8(-) --> CD34(+)1(+)3(-)4(+/-)8(-) --> CD34(-)1(+)3(-)4(+)8 (+/-) --> CD34(-)1(++)3(-)4(+)8(+). In this report, we examined cytoki ne receptor gene expression on these subsets by reverse transcription- polymerase chain reaction analysis (RT-PCR). We were able to detect in terleukin-7 receptor (IL-7R), c-kit and IL-2R gamma in all CD34(+) thy mocyte subsets, consistent with previous functional studies. We found IL-1R, granulocyte/macrophage colony-stimulating factor receptor-alpha and IL-LCR transcripts in CD3(-) and CD34(+) subsets. Secondly, we in vestigated T cell receptor (TCR)-delta and -beta gene rearrangement an d transcription in CD34(+) thymocytes. Our results show that a full-le ngth TCR-delta transcript and the recombination activating genes RAG-1 and RAG-2 mRNA were already expressed in the CD34(+)1(-) subset. Matu re V beta-containing TCR transcripts were also detected in the CD34(+) 1(+) subset: but not in the CD1(-) fraction. Furthermore, PCR analysis of D-J beta gene rearrangements showed that greater than or equal to 70% of CD34(+)1(-) cells are in a TCR beta germ-line configuration, al though D-J beta recombination had already started in this population.