lecture 6

Question 1

adaptive immune system is optimized to recognize

Answer 1

microbial macromolecules

Question 2

best antigens are

Answer 2

large, complex, stable, foreign proteins

Question 3

small molecules of less than 5000Da

Answer 3

are usually poor antigens

Question 4

small molecules may be made antigenic by linking them to

Answer 4

large proteins (carrier)

small molecules are haptens

Question 5

haptens

Answer 5

small molecules used as antigen carriers/antigenic - carrying small molecules by linking together

Question 6

epitopes

Answer 6

specific areas on the surface of foreign molecules that cells of adaptive immune system can use BCR/TCR to recognize

Question 7

five classes of immunoglobulins

Answer 7

IgG, IgM, IgA, IgE and IgD

all originate as B cell antigen receptors (BCRs) that are shed/secreted into body fluids

Question 8

IgG

Answer 8

predominant immunoglobulin serum
mainly responsible for systemic defense

blood, tissue, colostrom (predominant Ig) (13.5 mg/mL in serum)
memory responses!
opsonization (binds pathogens and toxins to host cells!)
complement activation
antibody dependent cellular cytotoxicity (ADCC)
neonatal immunity
binds phagocytes vie Fc receptors
secondary/memory responses

2 binding sites

Question 9

IgM

Answer 9

large immunoglobulin
mainly produced during primary immune response

blood only (1.5 mg/mL in serum)
first response to antigen
aggregates microbes and large antigens
complement activation
part of naive B cell antigen receptor

pentameric w J chain
10 binding sites

Question 10

IgA

Answer 10

produced on body surfaces
responsible for defense of intestinal & respiratory tract

blood, milk, mucosal surfaces (tears, saliva, gut, lungs) (3.5 mg/mL in serum)
prevent entry of pathogens
mucosal immunity

monomeric form in serum
dimeric form has 4 binding sites

Question 11

IgE

Answer 11

small quantities in serum
responsible for immunity to parasitic worms & allergies

blood and tissues (0.05 mg/mL in serum)
defend against helminthic/ectoparasites
allergy responses/immediate hypersensitivity
IgE + antigen complex activates mast cells and basophils to release vasoactive substances (histamine and serotonin)
2 binding sites

Question 12

IgD

Answer 12

found on surface of immature lymphocytes

part of BCR

Question 13

antigen

Answer 13

part of a pathgen/foreign molecule that is recognized by the immune system

Question 14

antigen recognition

Answer 14

soluble molecules (antibodies)
receptors for antigens are on B and T cells, these are antibodies

Question 15

immunogen

Answer 15

substance that induces immune response when injected into a host

Question 16

affinity

Answer 16

binding strength of an antibody for antigen

Question 17

avidity

Answer 17

accumulated strength of multiple affinities of individual binding interactions

Question 18

direct binding

Answer 18

antibodies recognize/bind exogenous antigens
resting b cell w Ig receptor -> encounter w antigen and binds -> stimulates B cell gives rise to antibody secreting plasma cells for beating out pathogen

Question 19

indirect binding

Answer 19

T cells recognize endogenous antigens using TCR

A. phagocytes w ingested microbes in vesicles (CD4+ effector T cells -> microbe) -> cytokine secretion -> a. Macrophage activation - killing of ingested microbes b. inflammation
B. infected cell w microbes in cytoplasm (bind to CD8+ T cells) -> kill infected cell!

Question 20

heteroantigen

Answer 20

foreign to body
infectious agent (living or dead)
environmental antigens
pollens
chemicals/drugs

Question 21

alloantigen

Answer 21

tissues or cells from a genetically dissimilar member of same species

Question 22

xenoantigen

Answer 22

tissues derived from a differnet species

Question 23

autoantigen

Answer 23

self or hosts own tissue

Question 24

foreign

Answer 24

not self or related

Question 25

molecular size

Answer 25

at least >1000 Da or 1kDa | best immunogens are 100kDa or bigger

Question 26

complexity

Answer 26

complex glycoproteins w tertiary structure | not simple repeating polysaccharides, lipids or nucleic acids

Question 27

strutural stability

Answer 27

not easily degraded (toxins) but not inert (plastics, silicon implants, tattoo dyes)

Question 28

BEST ANTIGENS ARE

Answer 28

FOREIGN, COMPLEX AND LARGE

Question 29

properties of antigens that detemine potency

Answer 29

foreign, large (>1kDa), complex, stable, route of administration, amount of antigen, host genetic makeup

Question 30

epitope

Answer 30

discrete site on antigen recognized by antibodies (host) or T cell receptors) may involve elements of the primary, secondary, tertiary or quaternary structure also called antigenic determinants

Question 31

antibody and t cell receptors recognize different epitopes on

Answer 31

the same antigen

Question 32

viral antigens examples

Answer 32

Rabies virus's immunodominant antigen | G glycoprotein spikes -> 400kDa has 16kDa immunodominant epitope

Question 33

bacterial antigens example

Answer 33

``` Pilli (F antigens) capsule (K) cell wall (O) flagellum (H) gram negative -> LPS gram positive has more peptidoglycan ```

Question 34

haptens

Answer 34

small antigenic molecules that can bind to antibody but are NOT immunogenic dont elicit immune responses unless BOUND to a carrier protein ex: drugs, hormones, toxins (too small) penicillin + albumin (carrier)

Question 35

major autoantigens of host cells

Answer 35

blood group antigens (erythrocytes) major histocompatility complex cluster of differentiation molecules (CD)

Question 36

MHC

Answer 36

expressed by all nucleated cells | imprtant for tissue recognition, transplantation medicine, antigen processing and presenting in adaptive immunity

Question 37

cluster of differnetiation molecules (CD)

Answer 37

molecules of biological function that define cell subsets | indentified by monoclonal antibodies

Question 38

immunoglobulin structure

Answer 38

antigen binding site w variable domains hinge region light chain heavy chain

Question 39

biological effector functions of antibodies

Answer 39

mediated by the binding of the Fc region (tail/heavy chain): 1. Fc receptors expressed by phagocytes, NK cells, Mast cells 2. plasma proteins -> complement proteins

Question 40

IgY

Answer 40

immunoglobulin found in yolk | bird version of IgG (memory responses)

Question 41

antibodies can bind in

Answer 41

linear or conformational epitopes (folded

Question 42

multivalent antigens

Answer 42

w different epitopes - requires all different antibodies | w same epitope and antibody

Question 43

antibodies are flexible due to

Answer 43

hinge region of strucutre | can be widely or closesly spaced