HLA-G*0105N null allele encodes functional HLA-G isoforms.
Expression of the nonclassical HLA class I antigen, HLA-G, is associated with immune tolerance in view of its role in maintaining the fetus in utero, allowing tumor escape, and favoring graft acceptance. Expressed on invasive trophoblast cells, HLA-G molecules bind inhibitory receptors on maternal T lymphocytes and NK cells, thereby blocking their cytolytic activities and protecting the fetus from maternal immune system attack. The HLA-G gene consists of 15 alleles, including a null allele, HLA-G*0105N. HLA-G*0105N presents a single base deletion, preventing translation of both membrane-bound (HLA-G1) and full-length soluble isoforms (HLA-G5) as well as of the spliced HLA-G4 isoform. The identification of healthy subjects homozygous for this HLA-G null allele suggests that the HLA-G*0105N allele may generate other HLA-G isoforms, such as membrane-bound HLA-G2 and -G3 and the soluble HLA-G6 and -G7 proteins, which may substitute for HLA-G1 and -G5, thus assuming the immune tolerogeneic function of HLA-G. To investigate this point, we cloned genomic HLA-G*0105N DNA and transfected it into an HLA-class I-positive human cell line. The results obtained indicated that HLA-G proteins were indeed present in HLA-G*0105N-transfected cells and were able to protect against NK cell lysis. These findings emphasize the role of the other HLA-G isoforms as immune tolerogeneic molecules that may also contribute to maternal tolerance of the semiallogenic fetus as well as tumor escape and other types of allogeneic tissue acceptance.
Le Discorde
Magali
M
Service de Recherches en Hémato-Immunologie, CEA-DSV-DRM, Institut d'Hématologie, Hôpital Saint-Louis, Paris 75010, France. teyssier@dsvidf.cea.fr
Le Danff
Caroline
C
Moreau
Philippe
P
Rouas-Freiss
Nathalie
N
Carosella
Edgardo D
ED
D000483:Alleles; D017398:Alternative Splicing; D003601:Cytotoxicity Tests, Immunologic; D004247:DNA / Q000235:genetics; D005260:Female; D005822:Genetic Vectors; D006680:HLA Antigens / Q000235:genetics* / Q000276:immunology*; D059951:HLA-G Antigens; D006801:Humans; D007108:Immune Tolerance; D007150:Immunohistochemistry; D007694:Killer Cells, Natural / Q000276:immunology; D016297:Mutagenesis, Site-Directed; D011247:Pregnancy; D020033:Protein Isoforms; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014162:Transfection; D020298:U937 Cells
D006680:HLA Antigens; D059951:HLA-G Antigens; C420206:HLA-G*01:05N antigen; D020033:Protein Isoforms; D012333:RNA, Messenger; D004247:DNA