Class II major histocompatibility complex (MHC) molecules bind peptides within the endocytic compartment and the class II/peptide complex is expressed at the surface of antigen presenting cells (APC) for inspection by CD4+ T cells. This process is critical to the immune surveillance of the extracellular and endosomal spaces. The long term objective of this proposal is to elucidate the molecular mechanisms and intracellular pathways involved in the formation of class II/peptide complexes within APC. As an approach, EBV-transformed B cell lines (B-LCL) are used as model APC to take advantage of the opportunity they afford to use somatic cell genetics in the dissection of a multi-step pathway. One interesting group of mutant B-LCL are defective in class II-restricted antigen presentation, despite expression of normal class II genes. In these mutants, the majority of class II molecules fail to become loaded with the normal spectrum of naturally processed peptides and are instead associated with fragments of the invariant chain, a class II molecular chaperone. The genetic basis of the defect in these mutants is mutation of the HLA-DMB gene, an MHC linked, relatively non-polymorphic class II-like gene. These results indicate that HLA-DM plays an essential role in the class II antigen presentation pathway in B-LCL, although its specific function is unknown. The primary goal of this proposal is to determine the mechanism of action of HLA-DM in class II restricted antigen presentation.
The specific aims are: (1) to determine whether HLA-DM expression alters trafficking of conventional class II MHC molecules in B lymphoblastoid cells; (2) to investigate the hypothesis that HLA-DM catalyzes release of invariant chain fragments and/or peptide-loading of conventional class II molecules, such as HLA-DR; (3) to determine if HLA-DM directly interacts with conventional class II molecules; (4) to investigate the basis of the temperature sensitive phenotype of a unique DMB mutant The approaches center on using mutant cell lines in biochemical, histological and cell biological assays. In addition, molecular genetic techniques will be used to generate new mutants to investigate the hypothesis that DR and DM directly interact. These studies should contribute to an understanding of a critical step in the class Il antigen presentation pathway and thus may have implications for diseases which involve class II-restricted T cells and for efforts to augment or dampen immune responses in humans.

Agency
National Institute of Health (NIH)
Institute
National Institute of Allergy and Infectious Diseases (NIAID)
Type
Research Project (R01)
Project #
3R01AI028809-11S1
Application #
6093994
Study Section
Allergy and Immunology Study Section (ALY)
Program Officer
Deckhut Augustine, Alison M
Project Start
1989-12-01
Project End
2001-06-30
Budget Start
1999-07-01
Budget End
2001-06-30
Support Year
11
Fiscal Year
1999
Total Cost
Indirect Cost
Name
Stanford University
Department
Pediatrics
Type
Schools of Medicine
DUNS #
800771545
City
Stanford
State
CA
Country
United States
Zip Code
94305
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Lee, Andrew W; Wang, Nan; Hornell, Tara M C et al. (2011) Human cytomegalovirus decreases constitutive transcription of MHC class II genes in mature Langerhans cells by reducing CIITA transcript levels. Mol Immunol 48:1160-7
Hou, Tieying; Macmillan, Henriette; Chen, Zhenjun et al. (2011) An insertion mutant in DQA1*0501 restores susceptibility to HLA-DM: implications for disease associations. J Immunol 187:2442-52
Pashine, Achal; Busch, Robert; Belmares, Michael P et al. (2003) Interaction of HLA-DR with an acidic face of HLA-DM disrupts sequence-dependent interactions with peptides. Immunity 19:183-92
Zarutskie, J A; Busch, R; Zavala-Ruiz, Z et al. (2001) The kinetic basis of peptide exchange catalysis by HLA-DM. Proc Natl Acad Sci U S A 98:12450-5