Lecture 6 - Antigens & MHC Flashcards
what are antigens
a foreign substance that will bind to MHC receptors
What are MHC
a set of genetic loci that helps immune cells differentiate foreign from self
What limits the innate immune system’s efficacy
Limited specificity, less potent, lacks memory
What cells express PRRs
innate immune cells
How is the adaptive immune system specific
employs antigen-specific lymphocytes (B and T)
How is the adaptive immune system systemic
targeted and reaches all parts of the body versus local responses
How does the adaptive immune system have memory
once exposed to an antigen, the animal will make a stronger and more immediate response to it via antibodies and memory cells
Epitope
site on an antigen recognized by specific receptors
Immunogens
antigens that induce an immune response after binding
T/F: ALL immunogens are antigens but NOT ALL antigens are immungoens
True
What makes an antigen “good”
the ability for it to be recognized by the immune cells
Whata are the characteristics of a “good” antigen
Large, complex, moderate degradability, foreign
What are microbial agents
bacterial or viral antigens
What are non-microbial agents
cell-surface, food-derived, inhaled, injected, etc.
what are autoantigens
a trigger that is self (autoimmune)
What are haptens
small, non-immunogenic proteins/molecules used to stimulate an immune response after binding to carrier proteins
What is an Antigen Presenting Cell
immune cell which presents antigens on their cell surface for the activation of T cells
What cell is the bridge between the innate and adaptive immune systems
dendritic cells
What cells are APCs
Dendritic cell, B cell, Macrophage
What do the dendritic processes contribute to in DC cells
adhesion and communication with T cells, antigen trapping
What are the four classes of DCs
- Classical
- Follicular
- Langerhans
- Plasmacytoid
What does Classical DC do
detect and capture antigens in the local environment and migrate to the lymph (The Golden Trio)
What does the Langerhans Cells do
detect antigens present in microbes of the skin and create a local response
What do Follicular DCs do
present antigens to B cells to activate them
What do Plasmacytoid DCs do
Release Type I and Type III interferons to trigger viral infection response
Pinocytosis
drink/intake of soluble material
T/F: Macrophages present antigens to naive t cells
False - present to already activated T cells
Identify APCs for exogenous antigens
DC
What is AG processing
native antigen is trimmed into smaller immunogenic fragments by the intracellular machinery of APCs
Activated (mature) DCs express high levels of what
MHC molecules and chemo secretions
Class I MHC
Most immune cells
present to cytotoxic T cells (C8)
Class II MHC
B cells, macrophages, DCs, T cells
present to helper T cells (C4)
What is the structure of MHC Class I
alpha chain (3 domains) bound to B2-microglobulin
T/F: MHC Class I binds shorter antigens than Class II
True
What is the structure of MHC Class II
alpha and beta chains
Summarize how exogenous antigens become presented and recognized
1 - APCs endocytose
2- digested by proteases
3- antigens binds to MHC class II endosomally
4 - carried to cell surface
5 - recognized by T helper cells
Summarize how endogenous antigens are presented and recognized
1 - antigens are fragmented by ubiquitination
2 - pass into ER lumen
3 - bind to MHC Class I
4 - carried to cell surface
5 - recognized by cytotoxic T cells
Summarize exogenous antigens
- bacteria, allergens
- captured and degraded by APC
- MHC II presents
- CD4+ (helper) T cells
Summarize endogenous antigens
- viruses, tumors
- processing by affected cell
- MHC I presents
- CD8+ (cytotoxic) T cells
What is cross-presentation?
When dendritic cells present exogenous antigens with MHC class I
What are superantigens?
Bind to outer edge of MHC-TCR complex
T cells are stimulated in non-specific way - CD4+ T cells produce large amounts of cytokines
T/F: too little MHC creates autoimmune conditions
False - too many
What are the two components of MHC genes
- multiple gene families (no rearrangements)
- Gene polymorphism (variable alleles)
T/F: MHC heterozygous individuals respond to a greater range of antigens
True
How many different MHC are there to provide resistance to disease and autoimmune effects
6
