MHC Flashcards
BCR
recognizes and binds to free antigen that is part of a larger pathogen or toxin
BCR complexes
- ITAMS
- CD19, CD81, CD21
ITAM
Igalpha
Igbeta
- transduce signals
CD19
transmit and relay signals to cell interior
CD81
transmit and relay signals to cell interior
CD21
transmit and relay signals to cell interior
TCR
recognizes and binds to both antigen-derived peptide and MHC to which peptide is bound
- Peptide sources can be from endogenously or exogenously processed antigens
TCR subunits
alpha and beta each have a constant region and variable region
Major histocompatibility complex
- binding groove of a cell-surface protein
- how TCR recognizes pieces of antigen
MHC
peptide made within the cell—> MHC molecule—>surface
MHC Class 1 and class 2
- membrane-bound glycoprotiens that are related in both structure and function
- Antigen-presenting molecules
- Form stable complexes with peptide ligands
- Display antigen on cellular surface for TCR engagement
- NEED PEPTIDE
Nucleated cells
MHC class 1
APCs or phagocytic cells
MHC class 2
MHC class 1
- Ig family (immunoglobulin domain=sticky domain_
- two peptides (larger transmembrane alpha chain and smaller beta2-microbglobulin protein)
- 8-10 amino acids
MHC class 2
- Ig superfamily
- heterodimeric transmembrane protein (alpha chain and beta chain)
- 13-18 amino acids
MHC class 1 functions
- Present peptide to CD8+ T cells (CTLs)
- Peptides derived from endogenous intracellular proteins
- Some amino acids anchor the peptide into the groove
- Other amino acids are available to interact with the TCR
MHC class 2 functions
- Usually derived from exogenous extracellular processed antigens
- Present antigen peptides to CD4+ T cells
- Anchor amino acids residues
Nature of peptide-binding groove for MHC class 1
closed at both ends
Nature of peptide-binding groove for MHC class 2
open at both ends
Role of MHC class 1
- Presents intracellular antigen peptides
- includes self-protein
- Provides a way for “checking” that cells are self and generally healthy
- Can show which cells have been infected with viruses or are abnormal and display those peptides on class 1 and activate CTLs
Where is MHC class 1 expression found?
Throughout the body essentially on all nucleated cells
Role of MHC class 2
- presents extracellular antigen peptides
- More restricted, generally found on cells involved in immune responses
- help direct responses against threats- things that shouldn’t be in our systems- and display those peptide and class 2 and activate th cells
MHC class 2 expression is primarily restricted to?
Antigen presenting cells
- macrophages
- B cells
- Dendtritic cells
Genetic regulatory components: transcriptional promoters that drive transcription during times of infections, _____ are core components transcriptional activators
PRRs
Viral interference: viruses like to shut down MHC class ____ expression because it targets the cells they’re in for destructions
1
Cytokine-mediated signaling: some cytokines like _______ and ________ can drive up MHC expression
Type 1 interferons
TNF pro-inflammatory
Drive Down
Antihistamines, steroids
MHC alleles
- co-dominantly expressed
- both maternal and paternal are expressed in offspring
- individuals express MHC alleles inherited from both parents
MHC allele diversity
- provides flexibility in responding to immune changes
- makes transplantation particularly difficult
MHC restriction
- T cells are restricted to recognizing peptides presented in the context of self-MHC alleles
