Unique biochemical properties of human leukocyte antigen-E allow for a highly specific function in immune recognition.
OBJECTIVE
Does a correlation exist between the expression of human leukocyte antigen (HLA) class Ia and HLA-E and what is its biological significance?


METHODS
HLA-E transcripts were detected by reverse transcriptase-polymerase chain reaction. Metabolically labeled HLA-E heavy chains were immunoprecipited and analyzed by one-dimensional isoelectric focusing. Mouse RMA-S cells defective with regard to transporter associated with antigen processing (TAP) function were transfected with HLA-E and human beta 2-microglobulin to investigate TAP dependence of the cell-surface expression of HLA-E.


RESULTS
HLA-E is transcribed regardless of the down-regulation of polymorphic HLA class Ia expression. HLA-E is transported to the cell surface in the absence of TAP-controlled peptide loading. In human cells, the amount of HLA-E protein is very low regardless of the presence of correct peptide ligands.


CONCLUSIONS
HLA-E regulates immune functions in cells that have down-regulated the expression of polymorphic HLA-class Ia molecules, either by preventing harmful natural killer cells from attacking targets that have physiologically decreased HLA-class Ia expression or by activating effector cells against virus-infected and tumor cells with impaired HLA-class Ia expression.
Weiss
E H
EH
Institut für Anthropologie und Humangenetik, Ludwig-Maximilians-Universität, München, Germany.
Cannich
A
A
Sprinks
M
M
Fernandez
N
N
Ulbrecht
M
M
D000818:Animals; D000911:Antibodies, Monoclonal; D006680:HLA Antigens / Q000096:biosynthesis / Q000235:genetics / Q000276:immunology*; D015395:Histocompatibility Antigens Class I / Q000096:biosynthesis / Q000235:genetics / Q000276:immunology*; D006801:Humans; D007525:Isoelectric Focusing; D051379:Mice; D011233:Precipitin Tests; D012333:RNA, Messenger / Q000032:analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012680:Sensitivity and Specificity; D014162:Transfection; D000097625:HLA-E Antigens
D000911:Antibodies, Monoclonal; D006680:HLA Antigens; D015395:Histocompatibility Antigens Class I; D012333:RNA, Messenger; D000097625:HLA-E Antigens