Antigens

Question 1

What does the Innate Immune System Recognize

Answer 1

a limited number of conserved PAMPs such as microbial nucleic acids or lipopolysaccharides in the bacterial cell wall

Question 2

What can the adaptive immune system respond to?

Answer 2

almost all of the foreign macromolecules present in an invading microorganism

Question 3

Antigens

Answer 3

substance specifically binds to antibodies or a cell surface receptor of B and T cells

Question 4

Characteristics of Antigens

Answer 4

molecules that trigger adaptive immune responses. They are either large proteins, glycoproteins, or lipoproteins. Many different antigens can be found in a single microorganism.

Question 5

Bacterial Antigens

Answer 5

Capsule (K antigens), Pili (F antigens), Flagellum (H antigens), Cell Wall (O antigens)

Question 6

Bacterial Toxins

Answer 6

toxic proteins secreted by bacteria or released into the surrounding environment when they die. Toxins are highly immunogenic proteins and stimulate the production of antitoxins

Question 7

Viral Antigens

Answer 7

nucleic acids, capsids, or matrix proteins

Question 8

Where are viral antigens expressed?

Answer 8

on the surface of the host cells

Question 9

Other microbial antigens

Answer 9

animals may be invaded by fungi, protozoan, parasites, arthropods, and helminths.

Question 10

Non-microbial antigens

Answer 10

food, inhaled dust. Foreign molecules may be injected directly into the body through a snake or mosquito bite or by a veterinarian

Question 11

Histocompatability Antigens

Answer 11

the cell surface proteins that trigger graft rejection

Question 12

Autoimmune Responses

Answer 12

immune responses against normal body components

Question 13

Autoantigens

Answer 13

antigens that induce autoimmunity. Can include hormones (thyroglobulin), structural components (basement membranes), complex lipids (myelin), intracellular components (mitochondrial proteins, nucleic acids, nucleoproteins), cell surface proteins (hormone receptors)

Question 14

Tumor Antigens (Neoantigens)

Answer 14

produced as a result of tumor-specific mutation during the malignant transformation of normal cells

Question 15

Superantigens

Answer 15

cause non-specific activation of T cells resulting in polyclonal T cell activation and massive cytokine release.

Question 16

What produces superantigens?

Answer 16

pathogenic viruses and bacteria, as a defense mechanism against the immune system

Question 17

Characteristics of good antigens

Answer 17

large, complex, stable, foreign

Question 18

What make the best antigens?

Answer 18

foreign proteins

Question 19

Carbohydrates

Answer 19

Simple polysaccharides are not good antigens because they are often degraded before the immune system has time to respond to them. More complex carbohydrates may be effective antigens, especially if bound to proteins

Question 20

Lipids

Answer 20

poor antigens because of their wide distribution, relative simplicity, structural instability, and rapid metabolism. When linked to proteins or polysaccharides, they can trigger immune responses

Question 21

Mammalian Nucleic Acids

Answer 21

poor antigens because of their relative simplicity and flexibility and because they are rapidly degraded

Question 22

Microbial Nucleic Acids

Answer 22

have a different structure with many unmethylated CpG sequences. Can stimulate potent immune responses

Question 23

Stainless Steel and Plastic

Answer 23

not antigens because they are inert and non-degradable.

Question 24

What is the ability to stimulate an immune response determined by?

Answer 24

route of administration, amount of antigen administered, and genetic makeup of the immunized animal

Question 25

Epitopes

Answer 25

prominent structural features on the surface of foreign molecules that are recognized by the immune system. Molecules will possess many different epitopes

Question 26

Immunogens (complete antigens)

Answer 26

Antigens that are able to generate immune response by themselves. These are usually proteins, peptides, or polysaccharides with high molecular weight

Question 27

Haptens (incomplete antigens)

Answer 27

antigens which are unable to generate the immune response themselves. Can be immunogenic if coupling with carrier proteins. Low molecular weight and non-protein substances

Question 28

Carrier Molecule

Answer 28

non-antigenic component that helps in provoking the immune response

Question 29

Cross-Reaction

Answer 29

Antigens directed against one antigen unexpectedly reacts with another apparently unrelated antigen. Results from the presence of shared epitopes on different antigens

Question 30

Cross-Reaction Example

Answer 30

antisera to bovine serum albumin cross-react strongly with sheep and goat serum albumin but weakly with serum albumin from other mammals

Question 31

How do superantigens bind non-specifically?

Answer 31

by cross-linking to the MHC and T cell receptor. This induces a signaling pathway that results in the proliferation of the cell and production of cytokines