Impairment of MHC class I transcription in a mutant bovine B cell line.
To better define the regulation and expression of bovine major histocompatibility complex (MHC) antigens, the bovine B lymphoblastoid cell line, BL3, was exposed to gamma-irradiation and surviving cells were immunoselected for MHC class I antigen loss. The resulting class I expression loss variant, BL3.1, was characterized at both the protein and genetic levels to ascertain the nature of the defect. Microfluorimetry analysis revealed a 3--5-fold surface density reduction of all class I products on BL3.1 cells relative to the parental BL3 cells. This decreased surface expression was specific for MHC class I and not for MHC class II or the non-MHC-linked gene product, immunoglobulin (Ig). Northern and quantitative slot blot analyses demonstrated a corresponding diminution of class I RNA in BL3.1 suggesting a transcriptional level defect. Nuclear run-off and transcription inhibition experiments confirmed no post-transcriptional changes while Southern blot analysis provided no evidence for alterations within or near the class I genes. To help elucidate the mechanism of altered class I expression, the parent, BL3, and variant, BL3.1, were cultured with factors known to enhance MHC class I transcription. Interferon (IFN)-gamma, lipopolysaccharide (LPS), and activated peripheral blood lymphocyte (PBL) supernatant cultured with both cell lines induced MHC class I transcription and surface expression 2--3-fold greater than the untreated controls. It is likely, therefore, that a genetic alteration outside of the class I genes has occurred within BL3.1 impairing expression of MHC class I.
Harms
J S
JS
Department of Veterinary Science, University of Wisconsin-Madison 53706.
Splitter
G A
GA
D000818:Animals; D001402:B-Lymphocytes / Q000276:immunology*; D015152:Blotting, Northern; D002417:Cattle; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D015536:Down-Regulation; D005434:Flow Cytometry; D015870:Gene Expression; D005805:Genes, MHC Class I; D015395:Histocompatibility Antigens Class I / Q000235:genetics*; D009154:Mutation; D012150:Polymorphism, Restriction Fragment Length; D012333:RNA, Messenger / Q000235:genetics; D014158:Transcription, Genetic
D015395:Histocompatibility Antigens Class I; D012333:RNA, Messenger