Dominant negative suppression of major histocompatibility complex genes occurs in trophoblasts.
BACKGROUND
Polymorphic class I and II major histo-: compatibility complex (MHC) genes are not transcribed in trophoblasts although many immune system cells express these genes constitutively. To study the molecular biology of MHC suppression for the purposes of potential transgenic animal development, we examined the effect on MHC expression in B cells by fusing them with trophoblasts.


METHODS
Trophoblasts and B cells with separate selection markers were fused with polyethylene glycol. After growth in double selection media, the hybrids were analyzed for HLA-A, -B, -C, -DR, -DP, and -DQ expression by fluorescence-activated cell scanning and class I and II mRNA by Northern blotting. Class II promoter activity in trophoblasts was then analyzed by transfection of a lethal reporter construct and subsequently, the class II transactivator.


RESULTS
Class I and II surface antigens and their corresponding mRNA were completely suppressed in the hybrids. The lethal reporter construct demonstrated that class II suppression resulted from lack of activation of the class II promoter. This in turn was caused by lack of functional class II transactivator.


CONCLUSIONS
These data indicate that dominant negative trophoblast factors, either directly or indirectly, suppress expression of the MHC genes. If these factors can be cloned, the potential exists for developing transgenic animals that cannot express MHC or peptide antigen to T cell receptors through the MHC system.
Coady
M A
MA
Department of Surgery, Yale University School of Medicine, New Haven, Connecticut 06510, USA.
Mandapati
D
D
Arunachalam
B
B
Jensen
K
K
Maher
S E
SE
Bothwell
A L
AL
Hammond
G L
GL
D015870:Gene Expression; D005799:Genes, Dominant; D005805:Genes, MHC Class I / Q000276:immunology*; D005802:Genes, MHC Class II / Q000276:immunology*; D015395:Histocompatibility Antigens Class I / Q000096:biosynthesis / Q000235:genetics; D000949:Histocompatibility Antigens Class II / Q000096:biosynthesis / Q000235:genetics; D006801:Humans; D006822:Hybrid Cells / Q000276:immunology / Q000378:metabolism; D007371:Interferon-gamma / Q000494:pharmacology; D011401:Promoter Regions, Genetic; D012313:RNA / Q000235:genetics; D012333:RNA, Messenger; D015534:Trans-Activators / Q000502:physiology; D014158:Transcription, Genetic; D014327:Trophoblasts / Q000276:immunology*; D014407:Tumor Cells, Cultured
D015395:Histocompatibility Antigens Class I; D000949:Histocompatibility Antigens Class II; D012333:RNA, Messenger; D015534:Trans-Activators; D012313:RNA; D007371:Interferon-gamma