Further serological and RFLP analysis of the MRL-+/+ and MRL-lpr/lpr mice.

During their ageing, MRL-lpr/lpr mice (H-2k) suffer from progressive lymph node enlargement, associated with the development of several acute autoimmune lesions. The primary effect and location of the lpr mutation is unknown. However, a minority of the lymphoid cells of some MRL-+/+, as well as MRL-lpr/lpr mice, express 'alien' H-2d antigenic specificities. In the course of the investigation of the origin of the latter, we have carried out the genotyping of the MHC of several MRL-+/+ and MRL-lpr/lpr mice using the Southern blotting technique and employing a variety of MHC class I and class II probes, and restriction enzymes known to discriminate between the d and the k haplotypes. None of the results obtained so far suggests the contribution of genuine H-2d genes to the MHC of the MRL-+/+ and MRL-lpr/lpr mouse strains. Alternative hypotheses for the generation of the 'alien' epitopes are discussed.