Isoforms of the nonclassical class I MHC antigen H2-Q5 are enriched in brain and encode Qdm peptide.
Although the human nonclassical class Ib major histocompatibility complex (Mhc) locus, HLA-G, is known to act as an immune suppressor in immune-privileged sites, little is currently known regarding participation of the rodent class Ib Mhc in similar pathways. Here, we investigated the expression properties of the mouse nonclassical Mhc H2-Q5(k) gene, previously detected in tumors and tissues associated with pregnancy. We find that H2-Q5(k) is alternatively spliced into multiple novel isoforms in a wide panel of C3H tissues. Unlike other known class I MHC, it is most highly transcribed in the brain, where the classical class Ia Mhc products are scarce. The truncated isoforms are selectively enriched in sites of immune privilege and are translated into cell surface proteins in neural crest-derived transfected cells. Furthermore, we present data supporting a model whereby Q5(k) isoforms serve an immune-protective role by donating their Qdm leader peptide to Qa-1, in a pathway homologous to the HLA-G leader fragment binding HLA-E and inhibiting CD94/NKG2A-positive cytotoxic cells. In addition, we report a previously unknown homolog of H2-Q5(k) in the C57BL/6 mouse, which encodes Qdm, but is transcribed solely into noncanonical isoforms. Collectively, these studies demonstrate that H2-Q5(k), and its homologous class I-like H2(b) gene may play tissue-specific roles in regulating immune surveillance.
Department of Immunology, The University of Texas Southwestern Medical Center at Dallas, 6000 Harry Hines Blvd, Dallas, TX 75390-9093, USA.
Nora E
NE
Renthal
Paula A
PA
Guidry
Sharmila
S
Shanmuganad
William
W
Renthal
Iwona
I
Stroynowski
D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001921:Brain / Q000276:immunology* / Q000378:metabolism*; D017931:DNA Primers / Q000235:genetics; D005260:Female; D005805:Genes, MHC Class I; D006183:H-2 Antigens / Q000235:genetics* / Q000378:metabolism*; D006801:Humans; D008297:Male; D051379:Mice; D008806:Mice, Inbred AKR; D008809:Mice, Inbred C3H; D008810:Mice, Inbred C57BL; D008969:Molecular Sequence Data; D010455:Peptides / Q000235:genetics* / Q000276:immunology* / Q000378:metabolism; D011247:Pregnancy; D020033:Protein Isoforms / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D014018:Tissue Distribution
D017931:DNA Primers; D006183:H-2 Antigens; D010455:Peptides; D020033:Protein Isoforms; C090580:Qdm protein, mouse; D012333:RNA, Messenger