Mechanisms of Antigen Processing and Presentation in Aging Dendritic Cells

Introduction
 » Goal
 » Specific Aims  

Subprojects
» Aging and Antigen Processing

» Autophagy and Antigen Presentation

» Spectratyping of Aging

» Characterization of lysosomal processing compartments

Members
Laura Santambrogio
Radhashree Maitra Ranjit Sahu              Yuri Naumov

Project 2 will investigate different aspects of antigen processing and presentation during immunosenescence.

In particular we will determine:

•  if the pathways utilized by exogenous and endogenous antigens for delivery to MHC class II compartments are compromised in aging

• the efficiency of MHC class II loading/presentation to T cells.  

• the pathways involved in delivery of self-proteins to MHC class II compartments by MA or CMA as well as exogenous antigens, which enter processing compartments following endocytosis. 

Endogenous and exogenous antigens delivery pathways

We recently were able to elute peptides from MHC class II proteins affinity purified from endosomal compartments. Several of these peptides derived from processed endogenous proteins entering lysosomal compartments through MA or CMA. These sequenced peptides represent the first processed antigens eluted directly from endosomal compartments and not from total cell lysates.

Antigen loading

Efficiency of antigen loading will also be determined in a quantifiable manner using a conformational specific antibody which recognizes specific MHC class II molecules loaded with the relevant peptide. 

Spectratyping

We will determine efficiency of T cell responses in each age group as well as possible differences in T cell clonal selection by Vb and Va spectratyping. Such analysis is particularly important because it would allow the determination of whether an homogeneous quantitative reduction in the T cell repertoire is accountable for the decreased immunological response in aged mice or whether a decrease in selected populations is observed. More importantly T cell spectratyping performed on antigen specific T cells from immunized mice will determine whether the clonal TCR expansion and immunological memory to the immunizing antigens is the same or different in each age group. This information will prove particularly useful in vaccine design for an aging population.

Immunolocalization of HLA-Dr in multilamellar bodies in dendritic cells.

expansion of the autopagic comparment in 22 months old rat dendritic cells

convergence of the autophagic and endocytic compartment in old dendritic cells green: mitotracker red: BSA-Tx Red