H-2 Class I molecules are trimeric complexes assembled in the ER and formed by the association of a 42-kDa heavy chain, b2 microglobulin and a short (8-11 AA) peptide. Although there is a profound reduction of H-2 Class I molecules in the b2m targeted mutation mouse, there is still residual expression of functional H2-Db molecules. In contrast, no H2-Db molecules can be detected by indirect immunofluorescence analysis of peripheral T lymphocytes from the H2-Db-/- mouse. A compensatory increase in cell surface expression of other class I molecules was observed resulting in almost unaltered levels of cell surface expression of b2m. This increase cannot be attributed solely to enhanced expression of Q7 or Q9 (the most abundant Class Ib molecules at the surface of T lymphocytes) or to H2-Kb implying that there may be increased cell surface expression of other, unidentified class Ib molecules. This mouse model is a useful tool for evaluating the immunological potential of individual MHC class I molecules and for studying cytolytic T cell education as well as the role of Class Ib molecules.
Origin: C57BL/6 mice deficient in Db were generated by homologous recombination in the laboratory of Dr. Francois Lemonnier of The Institut Pasteur, Paris France. Generation of H2-Db knockout mice: The H2-Db gene was disrupted using an insert containing LacZ and a neo cassette flanked by a 4-kb HindIII-XbaI 5' and 1-kb KpnI-SpeI 3' fragment of the Db gene resulting in the loss of the first three exons. The targeting construct was introduced into a CGR-8 embryonic stem cell of 129/OLA origin. Clones that were confirmed for homologous recombination were injected into B6 blastocysts and germline chimeras were identified. The founders were crossed twice with C57BL/6Ji females and heterozygous N2 offspring were intercrossed to generate the H2-Db homozygous strain. Inactivation of the H2-Db was confirmed by Southern blot analysis on tail DNA and immunofluorescence assay. Subsequently the N2 mice were backcrossed another 10 times to C57BL/6Ji and then intercrossed to produce N12 homozygous H2-Db-/- targeted mutation mice. Six pairs of the N12 homozygous mice were transferred from Dr. Lemonnier to the NIAID repository at Taconic in 2001 where they were embryo transfer derived.
Pascolo S, Bervas N, Ure JM, Smith AG, Lemmonier FA and Pérarnau B. HLA-A2.1-restricted education and cytolytic activity of CD8(+) T lymphocytes from beta2 microglobulin (beta2m) HLA-A2.1 monochain transgenic H-2Db beta2m double knockout mice. J. Exp. Med. 1997 Jun 16;185(12):2043-51.
Perineum B, Saron MF, San Martin BR, Bervas N, Ong H, Soloski MJ, Smith AG, Ure JM, Gairin JE and Lemonnier FA.Single H2Kb, H2Db and double H2KbDb knockout mice: peripheral CD8+ T cell repertoire and anti-lymphocytic choriomeningitis virus cytolytic responses. Eur. J. Immunol. 1999 Apr;29(4):1243-52.