A Viral Long Terminal Repeat Expressed in CD4⁺CD8⁺ Precursors Is Downregulated in Mature Peripheral CD4^-CD8⁺ or CD4⁺CD8^- T Cells

Abstract

The long terminal repeat from a thymotropic mouse mammary tumor virus variant, DMBA-LV, was used to drive the expression of two reporter genes, murine c-myc and human CD4, in transgenic mice. Expression was observed specifically in thymic immature cells. Expression of c-myc in these cells induced oligoclonal CD4+ CD8+ T-cell thymomas. Expression of human CD4 was restricted to thymic progenitor CD4- CD8- and CD4+ CD8+ T cells and was shut off in mature CD4+ CD8- and CD4- CD8+ T cells, known to be derived from the progenitor double-positive T cells. These results suggest the existence of similar and common factors in CD4+ CD8- and CD4- CD8+ T cells and support a model of differentiation of CD4+ CD8+ T cells through common signal(s) involved in turning off the expression of the CD4 or CD8 gene.

Specific Expression of the Human CD4 Gene in Mature CD4+ CD8- and Immature CD4+ CD8+ T Cells and in Macrophages of Transgenic Mice

“…As a negative control, an equivalent amount of RNA from nontransgenic mouse spleen was used. RNase-protected fragments were fractionated on 8% denaturing polyacrylamide gels (27).…”

“…The antibodies used in this study, phycoerythrin (PE)-coupled anti-human CD4 antibody Leu3a (Becton Dickinson), fluorescein isothiocyanate (FITC)-coupled antibody anti-murine CD4 GK 1.5), biotin-coupled anti-murine CD8 antibody Ly2, and FITC-coupled antimurine CD3 antibody 145-2C11, were previously described (27). The cell suspensions obtained from lymphoid organs were stained with antibodies as previously described (27). Detection of biotinylated antibodies was facilitated by using PE-avidin (Southern Biotechnology) as a second-step reagent.…”

“…Detection of biotinylated antibodies was facilitated by using PE-avidin (Southern Biotechnology) as a second-step reagent. Cells were analyzed on a FACScan (Becton Dickinson) as described previously (27).…”

“…The transgene DNA used for microinjection was excised as a 18.5-kbp EcoRI fragment. DNAs, purified by preparative agarose gel electrophoresis, were banded on CsCl as previously described (4,27).…”

“…Production of transgenic mice. One-cell (C57BL16 x C3H)F2 embryos were collected, microinjected, and transferred into pseudopregnant CD1 females essentially as described previously (4,27). The presence of the transgene was confirmed by Southern hybridization with tail DNA, using CD4 cDNA as a probe.…”