Extensive deletions in the Q region of the mouse major histocompatibility complex.

By use of Southern blot analyses and low copy number probes, the fine structure of the Q region of the mouse major histocompatibility complex was studied in more detail. With a probe recognizing the even-numbered genes Q4, Q6, and Q8, it was evident that Q4 and/or the regions flanking Q4 are polymorphic, whereas Q6 and Q8, and their flanking regions are nonpolymorphic. Perhaps the most noteworthy finding is that at least two strain haplotypes, H-2k and H-2f, possessed extensive deletions in the Q region. The most striking deletion was found in the H-2f haplotype, where the Q1 through Q9 genes appear to be missing. Because of these extensive deletions the functional importance of the Q region is questioned.