Antigens Flashcards
What is an antigen?
A molecule or part of a molecule recognized but he immune system
Immunogen
An antigen that evokes a specific immune response
Tolerogen
An antigen that creates does not lead to immune response though it should, immunologic tolerance
Type of Antigens
1) Endogenous
2) Exogenous
Endogenous Antigens
1) Autoantigens - a normal protein or molecule that is recognized by the body in an immune response - self antigen
2) Alloantigens - An antigen that is tissue specific and only present in one individual from a species (i.e. MHC/HLA)
3) Intracellular Pathogens - viruses, bacteria, etc.
Epitope
The part of the antigen that touches either the antibody or the MHC/HLA complex that is presenting it
T-Dependent Ags vs T-Independent Ags
T-Dependent - Antigen that requires help from B and T Cells to initiate an antigen response
T-Independent - Antigen that does not requires help from B and T cells to initiate a response (typically polysaccharides and lipids)
What portion of epitopes are recognized by T Lymphocytes?
The primary AA sequence are recognized by TCRs, not the free peptides
What are gamma/delta T-lymphocytes?
T cell that reside in the epithelial/muscosal areas of the body
Key features:
1) Can recognize DAMPS
2) Don’t discriminate on MHC/HLA class
3) Recognize lipid Ags
Immunodominant epitopes
Specific peptides out of many that can oknly be presented to the T cell to stimulate an immune response
Haptens
Molecules that need a carrier protein to induce an immune response - important for drugs (i.e. penicillin causes allergic rxn only when it interacts with proteins in the body)
What are superantigens?
Antigens that results in an excessive immune response (hyperactive) - examples include food poisoning and toxic shock syndrome bacteria
