Learning Objectives

• Identify the cells that are antigen-presenting cells (APC)
• Identify cells that express MHC I and/or MHC II molecules
• Compare and contrast antigen processing and presentation associated with MHC I and MHC II molecules
• Describe the role of antigen presenting cells in the activation of T cells with emphasis upon the role of the MHC molecules
• Describe the significance of immunological tolerance and how is it achieved

Major Histocompatibility Complex (MHC)

• in humans, what is MHC is also known as?
• what is the function of the MHC?
• what locus encodes the α and β chains of MHCI/II?
• what genes encode MHCI vs MHCII?
• compare the structural characteristics of MHCI/II?
• what does polygeny vs polymorphism mean? how do these $\uparrow$ MHC diversity?
• how many different types of MHC molecules can a cell express?
• what is the significance of polymorphism at a population level?
• what cells express MHCI vs MHCII molecules?

Endogenous & Exogenous Antigen

• what is antigen processing?
• what is endogenous vs exogenous Ag? why is this distinction important?