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EXPRESSION OF A FUNCTIONAL CHIMERIC lg-MHC CLASS II PROTEIN

Abstract

composed of the a- and ß-chains of the MHC class I1 I-E molecule fused to antibody V regions derived from anti-human CD4 mAb MT310. Expression vectors were constructed containing the functional, rearranged gene segments coding for the V region domains of the antibody H and L chains in place of the first domains of the complete structural genes of the I-E a- and ß-chains, respectively. Celltsr ansfected with both hybrid genes expressed a stable protein product on the cell surface. The chimeric molecule exhibited the idiotype of the antibody MT310 as shown by binding to the anti-idiotypic mAb 20-46. A protein of the anticipated molecular mass was immunoprecipitated witha nti-mouse IgG antiserum. Furthermore, human soluble CD4 did bind to thetr ansfected cell line, demonstrating that the chimeric protein possessed the binding capacity of the original mAb. Thus, the hybrid molecule retained: 1) the properties of a MHC class I1 protein with regardt o correct chain assembly and transport to the cell surface: as well as 2) the Ag binding capacity of the antibody genes used. Thgee neration of hybrid MHC class I1 molecules with highly specific, non-MHC-restricted bindingc apacities will be useful for studying MHC class 11-mediated effector functions such as selection of the T cell repertoire in thymus of transgenic mice

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