MODULE 3 - ANTIGENS AND ANTIBODIES Flashcards
(50 cards)
These are molecules that generate an immune response; foreign molecular structures.
Antigen or immunogen
It is the ability of a molecule to be recognized by an antibody or lymphocyte.
Antigenicity
What are the major components of bacterial surface?
- Cell wall
- Capsule (K antigens)
- Pili (F or K antigens)
- Fimbriae and flagella (H antigens)
Differentiate the peptidoglycan layer of gram positive and gram negative bacteria.
- Gram (+) - largely composed of peptidoglycan
- Gram (-) - layer of peptidoglycan is thin covered by an outer membrane consisting of lipopolysaccharide
Bacterial lipopolysaccharides in gram-negative bacteria are also called ?
Endotoxins
These are highly immunogenic proteins and stimulate the production of antibodies called _____.
Exotoxins/antitoxins
When exotoxins/antitoxins are treated with formaldehyde; it will lose its toxicity but retains its antigenicity and thus it will be modified and called ?
Toxoids
In virus, these are good antigens and are highly capable of provoking antibody formation.
Capsid proteins
Give some examples of non-microbial antigens.
- Food (allergen)
- Inhaled dusts
- Snake bite/mosquito bite
Compare the size of good antigen and poor antigen.
- Good antigen - large proteins (>1000 Daltons)
- Poor antigen - smaller proteins (<1000 Daltons)
Compare the complexity of good antigen and poor antigen.
- Good antigen - more complex carbohydrates (e.g. cell wall antigens of gram (-) bacteria)
- Poor antigen - simple polysaccharides (e.g. starch, glycogen)
Compare the degradability of good antigen and poor antigen.
- Good antigen - not readily degraded (e.g. microbial nucleic acid)
- Poor antigen - rapidly degraded (e.g. mammalian nuclei acid)
Compare the size of structural stability of good antigen and poor antigen.
- Good antigen - structurally stable
- Poor antigen - no fixed shaped (e.g. flagellin)
What are the factors that significantly influence the antigenicity of molecule?
- Size
- Complexity
- Dose
- Route of administration
- Host genetics
- Chemical stability
- Foreignness
Why can’t steel bones and plastic heart valves elicit an immune response?
- Due to molecular uniformity and inertness
- These polymers cannot be degraded and processed by cels
These are sites on the surface of an antigen that stimulates a specific immune response.
Epitopes or antigenic determinants
Small molecule that cannot initiate an immune response unless it is bound to an immunogenic carrier molecule.
Haptens
Give some example of haptens.
- Antibiotic penicillin (small nonimmunogenic molecule) → forms “penicilloyl” group when degraded in the body → bind to serum proteins such as albumin → penicilloyl-albumin complex → penicilloyl hapten → recognized as foreign epitope in some individuals → antibodies response and cause allergic reaction
- Resin of poison ivy plant called urushiol → binds to protein it comes in contact (e.g. skin proteins of person who rubs against the plant) → modified skin proteins → regarded as foreign → attacked my lymphocytes → allergic contact dermatitis
The antigenic molecule to which the haptens are attached is called the ?
Carrier
These are instances that identical or similar epitopes can be found on apparently unrelated molecules.
* Antibodies directed against one antigen may react unexpectedly with an unrelated antigen.
* Antibodies directed against a protein in one species may also react in detectable manner with homologous or similar protein in another species.
Cross-reactivity
They bind to specific antigens and facilitates removal by phagocytes, activate complement and neutralize the activity of the antigen.
Antibodies
Once B cell response is triggered, the receptors are shed into the surrounding fluids, where they act as _____.
antibodies
Antibodies are composed of 2 pairs of protein. What are these?
Heavy and light chain
The heavy and light chain of antibodies are linked together by ?
Disulfide bond
