MHC class II molecules are loaded with their peptide cargo in endosomal compartments. This process is catalyzed by the class ll-like molecule, HLA-DM (DM; H2-M in mice). HLA-DO (DO; H2-O in mice), an MHC-encoded, class ll-like molecule, associates with DM both during and after transport to endosomal compartments. Intriguingly, unlike all other components of the class II processing pathway, DO expression is restricted to B cells and thymic epithelial cells. It is now clear that DO modifies the peptide loading activity of DM. Less clear is the net effect of DO; DO can promote or inhibit class II peptide loading depending on the experimental system. The restricted expression of DO/H2-O to B cells has led us to hypothesize that H2-O exerts its affects predominantly on antigens (Ags) internalized via the B cell receptor (BCR). Our preliminary data shows that BCR ligation causes rapid dissociation of H2-O from H2-M and, also a dramatic compartmentalization of free H2-M with the internalized BCR. Focusing the critical components of Ag presentation within one compartment clearly suggests a mechanism by which H2-O substantially enhances class II presentation only after the BCR engagement of the BCR with Ag. Such an """"""""Ag focusing"""""""" mechanism would appear to be critical for T-dependent B cell immune responses, particularly for B cells expressing low affinity BCR. These concepts will be directly examined in this application.
In aim 1 we will 1) confirm and extend our studies examining H2-O dissociation from H2-M in BCR-ligated cells; 2) identify the subcellular compartments to which H2-O and H2-M traffic; and 3) examine the impact that H2-O dissociation has on class II presentation.
In aim 2, we will determine the role H2-O plays in T cell-dependent immune response in vivo. The effect of H2-O expression on T cell-dependent, antigen specific antibody responses and germinal center formation will be examined. We will also study the impact of H2-O on somatic hypermutation, affinity maturation and B cell positive selection. The proposed studies will elucidate the role of H2-O in the class II antigen-processing pathway in vivo, during immune responses. These studies are relevant for tumor immunity, autoimmunity and vaccine development.

Agency
National Institute of Health (NIH)
Institute
National Institute of Allergy and Infectious Diseases (NIAID)
Type
Research Project (R01)
Project #
5R01AI061484-03
Application #
7175420
Study Section
Cellular and Molecular Immunology - B (CMI)
Program Officer
Gondre-Lewis, Timothy A
Project Start
2005-02-15
Project End
2010-01-31
Budget Start
2007-02-01
Budget End
2008-01-31
Support Year
3
Fiscal Year
2007
Total Cost
$432,844
Indirect Cost
Name
Sloan-Kettering Institute for Cancer Research
Department
Type
DUNS #
064931884
City
New York
State
NY
Country
United States
Zip Code
10065
Denzin, Lisa K; Khan, Aly A; Virdis, Francesca et al. (2017) Neutralizing Antibody Responses to Viral Infections Are Linked to the Non-classical MHC Class II Gene H2-Ob. Immunity 47:310-322.e7
Porter, Gavin W; Yi, Woelsung; Denzin, Lisa K (2011) TLR agonists downregulate H2-O in CD8alpha- dendritic cells. J Immunol 187:4151-60
Yi, Woelsung; Seth, Nilufer P; Martillotti, Tom et al. (2010) Targeted regulation of self-peptide presentation prevents type I diabetes in mice without disrupting general immunocompetence. J Clin Invest 120:1324-36
Draghi, Nicole A; Denzin, Lisa K (2010) H2-O, a MHC class II-like protein, sets a threshold for B-cell entry into germinal centers. Proc Natl Acad Sci U S A 107:16607-12
Deshaies, Francis; Diallo, Djibril A; Fortin, Jean-Simon et al. (2009) Evidence for a human leucocyte antigen-DM-induced structural change in human leucocyte antigen-DObeta. Immunology 127:408-17
Fallas, Jennifer L; Yi, Woelsung; Draghi, Nicole A et al. (2007) Expression patterns of H2-O in mouse B cells and dendritic cells correlate with cell function. J Immunol 178:1488-97
Tran, An X; Whittimore, Judy D; Wyrick, Priscilla B et al. (2006) The lipid A 1-phosphatase of Helicobacter pylori is required for resistance to the antimicrobial peptide polymyxin. J Bacteriol 188:4531-41