Replacement of murine by human CD4 and introduction of HLA-DR17 in mice: Atriple-transgenic animal model to study human MHC II-CD4 interaction in situ

Functional studies with monoclonal antibodies (mAbs) against human surface molecules in situ are restricted for ethical reasons. On the other hand, ex perimental results obtained from in vitro assays might be of limited releva nce to the in vivo situation. Therefore, advanced animal models using human transgenic epitopes may be of value. To study the influence of anti-human CD4 mAbs on the MHC class II-CD4-interaction in situ, we combined by select ive breeding endogenous (murine) Cd4 deficiency with transgenic expression of human CD4 and HLA-DR17 (alpha and beta chain) in one mouse stock: TgN(HL A-DR17 alpha/beta) 1Dkfz - TgN(hCD4)1Lit - Cd4(tm1Lit) Animals suitable for further breeding were primarily selected based on flow cytometric data, an d testcrosses to identify the various genotypes (homo- or heterozygosity) f or the different surface molecules. In selected individuals, flow cytometry was supplemented with PCR-based analysis of genomic DNA. Therefore, primer s were selected to amplify transgenes, endogenous Cd4, and the targeting ve ctor leading to its inactivation (Cd4-knock out). Here we present flow cyto metrical and PCR analyses of the founder strains and the distribution of th e transgenes within the progeny. Using TgN(HLA-DR17 alpha/beta)1Dkfz TgN(hC D4)1Lit - Cd4(tm1lit) mice we will establish animal models of immunopathoge nic diseases in order to examine therapeutic efficiencies of anti-human CD4 and/or HLA-DR mAbs.