Expression of T-cell receptor alpha-chain genes in transgenic mice.
To examine the influences responsible for shaping the T-cell repertoire in vivo, we have introduced T-cell receptors of defined specificity into mice. In this report, we analyze transgenic mice carrying a T-cell receptor alpha-chain gene from a pigeon cytochrome c-reactive T-cell line. A variant of this construct, which has the immunoglobulin heavy-chain enhancer inserted into the JC intron, was also introduced into mice. Addition of the enhancer increased the steady-state level of transgene-encoded mRNA three- to fivefold in cultured T cells, leading to a two- to threefold increase in surface expression. In vivo, the difference between these two constructs was even more significant, increasing the number of transgene-positive cells from approximately 5 to 70% and the T-cell receptor surface density two- to threefold. Surprisingly, while surface expression of either type of transgene was limited to T cells, we found little tissue specificity with respect to transcription. In T cells expressing the alpha chain from the enhancer-containing construct, immunoprecipitation with a 2B4 alpha-specific monoclonal antibody revealed the expected disulfide-linked dimer. Costaining of these T cells with the 2B4 alpha-specific monoclonal antibody versus anti-CD3 indicated that expression of the transgene-encoded alpha chain precludes expression of endogenous alpha chains on the majority of cells; in contrast, 2B4 alpha-chain expression from the construct lacking the enhancer is inefficient at suppressing endogenous alpha-chain expression. In mice of the enhancer lineage, Southern blot analysis indicated suppression of endogenous alpha-chain rearrangements in T-cell populations, consistent with the observed allelic exclusion at the cellular level. Interestingly, newborn, but not adult, mice of this lineage also showed an increase in retention of unrearranged delta-chain loci in thymocyte DNA, presumably resulting from the suppression of alpha-chain rearrangements. This observation indicates that at least a fraction of alpha:beta-positive T cells have never attempted to produce functional delta rearrangements, thus suggesting that alpha:beta and gamma:delta T cells may be derived from different T-cell compartments (at least during the early phases of T-cell differentiation).
Berg
L J
LJ
Department of Microbiology and Immunology, Stanford University School of Medicine, California 94305.
Fazekas de St Groth
B
B
Ivars
F
F
Goodnow
C C
CC
Gilfillan
S
S
Garchon
H J
HJ
Davis
M M
MM
D000483:Alleles; D000818:Animals; D015139:Blotting, Southern; D005434:Flow Cytometry; D005796:Genes; D046911:Macromolecular Substances; D051379:Mice; D008815:Mice, Inbred Strains; D008822:Mice, Transgenic; D011544:Pseudogenes; D011948:Receptors, Antigen, T-Cell / Q000235:genetics*; D013601:T-Lymphocytes / Q000276:immunology; D014158:Transcription, Genetic; D014162:Transfection
D046911:Macromolecular Substances; D011948:Receptors, Antigen, T-Cell