W3.2 Flashcards
Immune response influences - Route of entry
Possible routes of entry:
- Oral route
- Subcutaneous route
- Intramuscular route
- Intravenous route
- Respiratory route
- Genitourinary route
- Ex. entry by gut = IgA; entry through skin = IgG
- Initial response mounted in spleen or lymph
Immune response influences - Genetic predisposition
Linked to major histocompatibility complex (MHC) and the receptors generated during T- and B-cell development
- MHC is a system of genes that code for cell-surface molecules that play an important role in antigen presentation
Epitopes
“Only a portion of the immunogen is recognized by the immune system
- antigenic determinant or epitope
- most protein immunogens have multiple epitopes “
T vs B Epitopes
”- Epitopes recognized by B cells may differ from those recognized by T cells
- T cells only recognize an epitope (linear) as part of a complex formed by the MHC proteins; immunogen must be degraded by the antigen-presenting cell (APC)
- B cell can recognize both linear and discontinuous/conformational epitope”
Linear Epitopes and T cells
”- the epitopes recognized by T-cell receptors are often buried
- the antigen must first be broken down into peptide fragments
- the epitope peptide binds to a self molecule, an MHC molecule
- the T-cell receptor binds to a complex of MHC molecule and epitope peptide “
Haptens
”- Small substance (antigen) that by itself does not initiate an immune response (not an immunogen); can be immunogenic by conjugation to a suitable carrier
- Once antibody production is initiated; can bind to antibody
A natural example of a hapten
Poison Ivy
Hapten importance in the lab
Synthetic (conjugate) vaccines
Adjuvant
Substance administered with the immunogen to increase the immune response
How adjuvant acts
“Acts by inducing a local response, attracts a large number of immune system cells to site
- Increases the size of the immunogen (multi-molecular aggregates)
- Prolongs the existence of the immunogen (traps antigen at injection site)
- Increases recruitment and activation of antigen-presenting cells (targets PRR on phagocyte -> release of cytokines)
Autoantigens
belong to the host; do not elicit an immune response under normal circumstances (autoimmune disease)
Alloantigens
“From other members of the host’s species; elicit an immune response
- Tissue transplants; blood transfusions”
Heteroantigens
From other species (animals, plants or microbes); elicit an immune response
Heterophile abs
- Antibodies reacting against Antigens that exist in unrelated plants or animals
- Heterophile antibodies often cross-react with other Ags (i.e. anti-bacterial polysaccharide Abs cross-react w human blood group A and B antigens)
- Sometimes heterophile antibodies can bind to animal Abs used in immunoassays giving false positive results
- EBV infection results in formation of large numbers of heterophile Abs (used diagnostically
