Variable expression of major histocompatibility complex class II in the domestic cat

This paper describes the characterisation of six independently produced monoclonal antibodies (mAbs) specific for non-polymorphic determinants of feline major histocompatibility complex (MHC) class II. One mAb is an anti-sheep class II which cross-reacts with the cat and five have been produced in response to immunisation with purified feline immunodeficiency virus. Despite their independent source all the mAbs have identical reactivities, immunoprecipitating two complex groups of polypeptides 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 revealed the complexity of feline class II mass and charge and implied the expression of multiple class II loci in the cat. Furthermore, it was demonstrated that distinct cell populations expressed a distinct range of class II variants. This suggesting either the differential expression or the distinct post-translational modification of lymphocytes from different sites. The mAbs have also been used for the detailed examination of the cellular distribution and tissue localisation of MHC class II in the cat.