Antigen Flashcards
Any molecular structure that when introduced is capable of Antibody reaction
Antigen
The capacity of the immune system to react to foreign or non-self objects is due to?
Major Histocompatibility Complex
Responsible for the molecular weight of the antigen
Carrier Portion
Important determinant as to whether an antigen can elicit or induce immune response
Carrier Portion
Responsible for the specificity of the antigen
Epitope
Interacts the with Fab portion of the antibody
Epitope
Other term for the part of antigen that is responsible for specificity of antigen
Determinant
Portion of the antibody where antigen binds
Antigen Binding Fragment (Fab)
What are the two (2) properties of antigen?
- Immunogenicity
- Antigenicity/Specificity
What are the three (3) factors that affect the immunogenicity of the antigen?
- Foreignness
- Size
- Chemical Complexity
Dictates the level of immune response
Foreignness
What are the four (4) antigen types in terms of foreignness?
- Autoantigen
- Alloantigen
- Heteroantigen
- Heterophile Antigen
Antigen that comes from the host species; does not induce immune response
Autoantigen
Disorder when the immune system attacks normal antigen in the body
Autoimmune disorder
Antigen that comes from the other member of the host species; may induce immune response
Alloantigen
Antigen type that causes transfusion associated reactions
Alloantigen
Antigen derived from other species (i.e. animals, plants, microorganism); capable of eliciting immune response
Heteroantigen
Type of antigen that is present in the microbial cell surface during infection
Heteroantigen
Type of antigen that is derived from unrelated species but are identical or closely related in structure
Heterophile Antigen
This type of antigen causes cross reaction with the antibodies that are produced by the immune response
Heterophile Antigen
Rich source of antigens
Graft
Other term for Graft
Tissue Transplant
Why is tissue typing important prior to transplantation?
Because graft or tissue transplant is a rich source or antigens. When a tissue is transplanted, it is capable of eliciting immune response; and the more antigen present, the greater the immune response.
How is graft differentiated?
Based on the source if tissue
What are the four (4) types of Graft?
- Autograft
- Isograft/Syngraft
- Allograft
- Heterograft/Xenograft
Graft type that comes from the host itself/ patient’s own body
Autograft
Graft type that is derived from identical individuals
Isograft/Syngraft
Graft type that is derived from non-identical individuals
Allograft
This is the most common tissue transplantation done in the hospitals
Allograft
Most common tissue/organ transplanted
Kidney
Most common liquid tissue/body fluid transfused
Blood
Type of graft that is derived from other species (i.e. plants, animals)
Heterograft/Xenograft
The factor of antigen immunogenicity dictates the number of epitopes present in the antigen
Size
Unit size of the antigen
Daltons
Antigen that has less than 10,000T molecular mass
Haptens
Molecular weight of immunogenic antigen
> 10,000 Da
Molecular weight of non-immunogenic antigen
< 10,000 Da
What is the molecular mass of Albumin?
30,000 to 60,000
Good antigen, stable antigen
Albumin
Excellent antigen; highly complex antigen
Hemocyanin
Molecular mass of hemocyanin
100,000 to millions Da
How can a hapten be immunogenic?
Hapten must have a carrier in order for it to become immunogenic
The best and strongest antigen
Protein
Why is protein the best and strongest antigen? (3 answers)
Because the peptide bonds that bind amino acids are covalently bonded which makes them highly stable.
Does not easily dissociate in plasma
Has longer circulation life
Overall chemical structure
Chemical Complexity
Why are nucleic acids, lipids, and amino acids least immunogenic?
They easily dissociate in the circulation
The ability to react specifically with the antibody or cell
that caused it to be produced
Antigenicity/Specificity
Why are antigens used in the laboratory as reagents?
Because target antibodies detected in the serum or plasma can specifically bind with these antigens
An incomplete antigen
Hapten
Most common carrier of hapten in the circulation
Albumin
Any substance that can induce an immune response
Immunogen
True or False: All antigen are immunogenic.
False. Not all antigens are immunogenic, because antigen may be an incomplete antigen which prevents them from inducing immune response.
True or False: All immunogens are antigenic.
True. An immunogen will always elicit immune response
Most fatal Hypersensitivity reaction
Type 1 Hypersensitivity
A special class of immunogen that induces
hypersensitivity reactions
Allergen
What happens during hypersensitivity reaction?
Immune response is exaggerated that it damages the tissue.
Substances added to an immunogen to enhance immune response
Adjuvants
Cause the immunogen to have greater immune reactivity
Adjuvants
Actions of Adjuvants (3)
▪ Prolongs the retention time of the immunogen in the body
▪ Increases the effective size of immunogen
▪ Stimulates the influx of macrophage and/or lymphocytes
Example of an adjuvant: A water in oil emulsion of Mycobacterium butyricum or Bordetella pertussis culture
CFA (Complete Freunds Adjuvants)
Bacteria present in CFA
M. butyricum and/or B. pertussis
Most commonly used adjuvant in clinical setting
Aluminum adjuvants
Examples of Adjuvants (3):
CFA
Lipopolysaccharide
Aluminum adjuvants
The strength of the attraction between an epitope and the antigen combining site of the antibody
Affinity
Refers to the strength of interaction between
complex antigens and antibodies
Avidity
Difference between avidity and affinity
the interacting part of the Antigen and Antibody
Simple interaction between a single epitope of antigen and Fab portion of antibody
Affinity
Sum total of strength of reaction between multiple epitopes of the antigens – involves complex antigens
Avidity