Three classes of mouse H-2 messenger RNA distinguished by analysis of cDNA clones

HLA cosmid clones show complete, widely spaced human class I genes with occasional clusters

To understand the organization of the human leukocyte antigen (HLA) gene region and its relationship to the transplantation antigens expressed at the cell surface we have isolated clones containing HLA class I genes from a cosmid library (Grosveld et al., Gene 13, 227, 1981) constructed with the DNA from an individual of defined haplotype. Most of the cosmids contain a single HLA gene in 30-40 kb of human DNA, indicating that human class I genes are rather widely spaced; two contain two genes and one contains three. Most of these genes appear to be complete; the double or multiple genes are found in the same orientation. Differences in restriction maps are evident but some common features are observed in particular in the 5' half of these genes.

Tissue-specific expression of an unusual H-2 (class I)-related gene

Sequence analysis of mouse H-2 cDNA clones has suggested the existence of an unusual class of H-2 (class I)-related antigens that, unlike the classical membrane-associated molecules, retains only the extracellular portion and is likely to be secreted. The expression of this class of H-2-related mRNA is tissue restricted; it is detectable in liver but not in brain, kidney, testis, thymus, or spleen. In the liver, its accumulation represents about one-fourth of all the H-2 (class I)-specific transcripts. This class of transcripts is present in mice of different inbred strains, but the level of expression differs markedly among them. A model is presented in which such a soluble form of the H-2 antigen would play the role of a blocking factor in maintaining peripheral inhibition of H-2 recognition. This would ensure tolerance of the H-2 molecule as a self antigen while permitting it to act as a guidance molecule for the associative recognition of viral and tumor antigens by cytotoxic T cells.