Lecture 8 - Triggers of Adaptive Immunity Flashcards
2 Rs of adaptive immunity
recognize and respond to almost all foreign macromolecules present in invading microbe
Antigens
foreign macromolecules in invading microbe
Antigenicity
inherent capacity of molecule to be recognized by immune system
Microbial antigens (3)
- bacterial antigens
- viral antigens
- fungi, protozoan parasites, arthropods, helminths
Non-microbial antigens
- cell surface antigens
- autoantigens
Examples of bacterial antigens
- peptidoglycans
- lipotechoic acid
- LPS
- lipoproteins
- capsular antigens (K)
- Pili (F)
- flagellar antigens (H)
- porins
- HSP
- exotoxins
- bacterial nucleic acids
Viral structure
nucleic acid surrounded by protein layer
Capsid
viral protein layer that surrounds nucleic acid core
Capsomere
subunits that make up capsid
What are good viral antigens
capsid proteins
What type of viral antigens can provoke adaptive immunity
viral proteins expressed on the surface of infected cells
What are other microbial antigens that can trigger adaptive immunity
structural components of many fungal pathogens, protozoan parasites, arthropods, and helminths
Microbial antigenicity vary and the adaptive response triggered ….
may not always be sucessful in protecting animal / eliminating invader
Non microbial antigens specific examples
- FOOD may trigger immune response and cause allergic reaction
- inhaled dust may have pollen grains
- blood-group antigens (glycoproteins)
- tissue graft reejction in genetically different individuals is triggered by histocompatibility antigens
- autoantigens
Autoantigens
induce autoimmune response, thyroglobulin, myelin, mitochondrial proteins, ect
3 characterisitics of best antigens
large, complex, and foreign
What reduces antigenicity
excessive or insufficient stability
Ability of an antigen to elicit immune response also depends on:
- route of administration
- amount of antigen adminstered
- genetic makeup of immunized animal
What antigens have the greatest antigenicity
large
What can increase the intensity of the immune response
greater the difference between foreign antigen and animal’s own antigens
Why do animals not recognzie self proteins
B-cells and T-cells that have the potential to recognize the self-proteins are eliminated from the body
What is directly proportional to its antigenicity
structural complexity
What specific antigens tend to be poorly antigenic
large repeating polymers such as lipids, nucleic acids, and carbohydrates
Why do flexible molecules such as flagellin and gelatin make poor antigens
BCR and antibodies cannot recognize unstable molecules that change conformation
How to increase antigenicity of flexible molecules
stabilizing by cross-linking
Why are antigens that are enzymatically broken down too quickly not antigenic
not enough time for recognition by BCRs and to be presented by APC
Why are simple polysaccarides such as starch and glycogen poor antigens
readily digested
In order to elicit an immune response, a molecule must
be degradable within APCs
Why are plastics and stainless steel generally NOT antigenic
large organic molecules that make up plastics form uniform repeated polymers which are very inert
What happens to inert molecules
cannot be broken down and presented to TCR to initiate an immune response
In general, what makes best antigens
large, complex proteins
What can large polysaccarides be complexed with to be highly antigenic
proteins
What immune response do glycoproteins illicit
antibodies are directed specifically against the polysaccharide moiety of the molecule
Why are lipids and nucleic acids poor antigens
readily degradable
What nucelic acids are antigenic
in nucleoproteins bc the NA is lined to the carrier nucleoprotein
Epitope/antgenic determinant
specific regions on large molecules against which immune responses are directed
immunodominant epitope
in a complex protein molecule, multiple epitopes are recognized by the immune system.
There is about 1 epitope per __ kDa of protein
5
If small molecules are chemically linked to a large protein molecule, ….
new epitopes will be formed on surface of large molecule and the complex will trigger immune response
Haptens
small molecules that can function as epitopes only when bound to other larger molecules
Carrier
antigenic molecule to which the haptens are attached
Toxic component of poison ivy that can bind to any protein it contacts
urushiol
PAthway of poison ivy allergiy contact dermatitis
- urushiol binds with skin proteins of person who rubs against plant
- modified skin proteins are treated as foreign and attacked by lymphocytes
- allergic contact dermatitis
Cross-reactivity of antigens
Identical or similar epitopes may sometimes be found on apparently unrelated molecules. Antibodies directed against one antigen may thus react with an unrelated antigen.
examples of cross-reactivity of antigens
- bacterial or food antigen carrying epitode for blood group glycoprotein
- Brucella abortus and some strains of Yersinia enterocolitica
- Feline infectious peritonitis (FIP) and virus of pig transmissible gastroenteritis (TGE)
