Antigens Flashcards
What two types of lymphocytes are antigen-presenting cells, and where are they each produced?
T cells (thymus gland) and B cells (bone marrow)
Where do antigen-proteins reside on bacterial, viral, protozoal and helminthic organisms?
On the surfaces
What is an antigen?
A (foreign) substance that is capable of eliciting an immune response/antibody generation, and capable of binding to an antibody
What do immunogenicity/antigenicity mean?
Immunogenicity: the ability of an immunogen to induce a strong immune response
Antigenicity: the ability of an antigen to be specifically recognized by antibodies generated from the induced immune response
What features make an ideal antigen?
- Large in size
- More chemically complex (AA seq., protein structure)
- Increased stability/rigid structure
- Increased degradability
- Increased foreignness (self antigen v. non-self antigen; furthest away evolutionarily)
What occurs if the [antigen] is too low?
Lymphocytes will be unresponsive –> “tolerance” by the I.S.
What occurs if the [antigen] is too high?
“Paralyzation” of the I.S. –> failure to produce an I.R.
What is the importance of booster shots with regard to the specificity of antigen-antibody binding?
This binding process is HIGHLY SPECIFIC; any changes to the chemical structure or physical shape of the antigen will PREVENT binding. Booster shots help to maintain the integrity of the introduced antigen so an I.R. can be created.
What is the relationship between antigenic epitopes and immune responses?
Antigenic epitopes are regions of specific AA sequence present on an antigen that each correspond to a specific lymphocyte’s antigen receptor
Describe the penicillin example discussed in class.
Penicillin –> breaks down into “Pencilloyl” // a hapten (small-molecule antigen)
Non-Allergic People: albumin ( a large-molecule blood protein) does NOT have the right shape to bind to Pencilloyl –>
Allergic People: albumin DOES have the right shape to bind to Pencilloyl –> becomes a large antigen –> a new antigenic epitope forms atop the Pencilloyl // hapten –> an I.R. is induced
Why does cross reactivity occur among antigenic epitopes?
Antigenic epitopes have short AA sequences,
Why does cross reactivity occur among antigenic epitopes?
An antibody may bind to an antigen different from the one it was raised to do so with, due to structurally similar but different epitopes among antigen molecules (related or un-related in nature).
E.g., epitopes on a walnut v. pecan; banana v. latex)
What are pros and cons to cross-reactive epitopes? What is “molecular mimicry”?
Pros: broad-spectrum immunity by the less-specific antibody
Cons: risk of the less-specific antibody attacking the body’s own self-antigens (molecular mimicry)
What happens if the immune response fails to come down once an antigen has been eliminated?
Chronic inflammatory disease
