VARIABLE EXPRESSION OF MAJOR HISTOCOMPATIBILITY COMPLEX CLASS-II IN THE DOMESTIC CAT

This paper describes the characterisation of six independently produce d monoclonal antibodies (mAbs) specific for non-polymorphic determinan ts of feline major histocompatibility complex (MHC) class II. One mAb is an anti-sheep class II which cross-reacts with the cat and five hav e been produced in response to immunisation with purified feline immun odeficiency virus. Despite their independent source all the mAbs have identical reactivities, immunoprecipitating two complex groups of poly peptides of M(r) 33 to 36.000 (MHC class II alpha chains) and M(r) 28 to 31,000 (MHC class II beta chains). Immunoblot analysis showed them to be beta chain-specific. One and two-dimensional electrophoresis rev ealed the complexity of feline class II mass and charge and implied th e expression of multiple class II loci in the cat. Furthermore, it was demonstrated that distinct cell populations expressed a distinct rang e of class II variants. This suggesting either the differential expres sion or the distinct post-translational modification of lymphocytes fr om different sites. The mAbs have also been used for the detailed exam ination of the cellular distribution and tissue localisation of MHC cl ass II in the cat.