Module 2: Antigens and antibodies

Question 1

antigen

Answer 1

a variety of large molecular structures that can interact with an antibody or a t cell receptor

Question 2

immunogens

Answer 2

antigens that are recognized by a persons immune system as foreign or abnormal and which therefore cause an immune response
Not all antigens are immunogens

Question 3

tolerogens

Answer 3

antigens for which an individual developed tolerance in contrast to an immunogen which evokes an immune response.
Self antigens are usually tolerated

Question 4

Allergens

Answer 4

antigens that elicit production of IgE antibodies instead of IgM/IgG of normal immune response

Question 5

Antigenicity

Answer 5

potency of an antigen

Question 6

Hapten

Answer 6

chemically active substance with LOW molecular weight that is unable to induce an immune response by itself but when conjugated with a carrier molecule, it becomes immunogenic

Question 7

heterophile antibodies

Answer 7

endogenous antibodies present in human serum that may interfere with various immunoassays

Question 8

Heterophile antigens

Answer 8

an antigen common to more than one species

ex. exposure to e coli early in life initiates anti B production in blood group A and O individuals

Question 9

epitope

Answer 9

epitope of an antigen is the exact structural component either on or within an antigen with which an antibody reacts

AKA antigenic determinant

Question 10

Carrier region

Answer 10

regions on the antigen structure to which antibody is not formed

Question 11

Specificity

Answer 11

exact anatomic and molecular characteristics of the epitope that enables it to be recognized and classified

Question 12

9 factors affecting ability of antigen to evoke an immune response

Answer 12

Chemical nature of antigens (proteins/IgG are best; polysaccharides/IgM less immunogenic; lipids, nucleic acids and inorganic substances not immunogenic)

Chemical complexity

Molecular size

Structural conformation of the molecule

Ionic charge (high charge could decrease immunogenicity)

Foreignness

Route, dosage, frequency of exposure to immunogen

Genetic composition of host (age, health)

Adjuvants

Question 13

Adjuvants

Answer 13

agents that can be administered with antigen that enhance the immune response

not immunogenic on their own

Question 14

2 ways antibodies are produced by b lymphocytes and secreted through the exocytosis pathway

Answer 14

Membrane bound

Secreted form

Question 15

Membrane bound antibody production

Answer 15

antibody serve ad the b cell antigen receipt (site on b cell which will bind with corresponding antigen)
If they make contact with specific antigen, B cell differentiates and becomes an antibody forming plasma cell

Question 16

Secreted form antibody production

Answer 16

plasma cells secrete free antibody into the blood or lymph

Secreted ab promote phagocytosis, neutralize antigens and activate complement

Question 17

2 types of light chains

Answer 17

kappa

lambda

Question 18

5 kinds of heavy chains

Answer 18

differentiate the class of antibody

IgM mu chains
IgG gamma chains
IgA alpha chains
IgD delta chains
IgE epsilon chains

Question 19

domains

Answer 19

loops of about 110 amino acids in the heavy and light chains

Question 20

constant domains of heavy chains

Answer 20

have the same amino acid sequence for all antibodies in a class

Question 21

constant domains of light chains

Answer 21

have the same amino acid sequence for either kappa of lambda light chains

Question 22

Variable domains (VH and VL)

Answer 22

have amino acid sequences that are specific to the epitope of the antigen that induced antibody production

Question 23

function of variable light domain

Answer 23

determines antibody specificity

site of antigen binding

Question 24

function of constant light domain

Answer 24

determines if chain is kappa or lambda

orientates antibody during antigen binding

Question 25

function of variable heavy domain

Answer 25

determines antibody specificity | site of antigen binding

Question 26

function of constant heavy 1 domain

Answer 26

orientates antibody during antigen binding

Question 27

function of constant heavy 2 domain

Answer 27

involved in complement activation

Question 28

function of constant heavy 3 domain

Answer 28

involved in phagocyte binding

Question 29

Fab (fragment antigen binding) fragment

Answer 29

consists of entire light chain and half of heavy chains NH2 (amino) end of the antibody Site that recognizes and binds antigen (epitope)

Question 30

Fc fragment (fragment crystallizable)

Answer 30

consist of other half of heavy chain COOH end Functions: Complement activation Macrophage attraction when coating an antigen Placenta expresses Fc receptors; allow binding of maternal IgG molecules for transport across placenta to baby May be labeled for in vitro detection of antigen

Question 31

Isotypes

Answer 31

different classes and sub classes of antibodies and are defined by differences in the constant domains of the heavy chains

Question 32

Allotypes

Answer 32

antibodies that are products of allelic genes

Question 33

Idiotope

Answer 33

the unique amino acid sequence found in variable region of heavy and light chains of antibody AKA Complementarity determining region CRD, hypervariable region HVR

Question 34

Idiotype

Answer 34

the sum of the unique amino acid sequences found in the variable domain of the H and L chains of an antibody at or near the antigen binding site

Question 35

About IgG

Answer 35

Heavy chains: 2 gamma chains (monomer) Crosses placenta? yes Function: opsonization, complement activation, neonatal immunity Isotypes: IgG1, IgG2, IgG3, IgG4 Binds complement? yes, esp. IgG1 and IgG3

Question 36

About IgM

Answer 36

Heavy chains: 10 mu chains (pentamer) Function: 1st antibody produced by newborn, activates complement, acts as naive b cell antigen receptor Binds complement? yes

Question 37

About IgE

Answer 37

Heavy chains: 2 epsilon chains (monomer) Function: immediate hypersensitivity, parasitic infections Binds complement? no

Question 38

About IgA (serum)

Answer 38

Heavy chains: 2 alpha chains (monomer) Function: mucosal immunity, found in colostrum Isotypes: IgA1, IgA2

Question 39

About IgA (secreted)

Answer 39

Heavy chains: 4 alpha chains (dimer) Function: mucosal immunity Isotypes: IgA1, IgA2

Question 40

About IgD

Answer 40

Heavy chains: 2 delta chains (monomer) | Function: Naive b cell antigen receptor, increased in some auto-immune diseases

Question 41

IgA makes up about __% of the antibody we produce everyday and is produced in the _____________

Answer 41

70% | mucosal lymphoid tissue

Question 42

IgA use in the body

Answer 42

transported through epithelial cells to the lumen of the GI or resp tracts Secreted IgA recognizes antigen and binds to it, preventing it from adhering and entering through the epithelium also, Opsonization leads to phagocytosis

Question 43

The first line of defence against bacteria and viruses is

Answer 43

secretory IgA | Secretory component helps antibody resist breakdown by proteolytic enzymes of the GI tract

Question 44

what is a babys immunity before they produce IgG themselves

Answer 44

``` IgG from mom through placenta After birth, IgA in maternal milk First 6 months: maternal IgG levels decline as baby begins their own immunoglobulin synthesis IgM starts 3 months before birth IgG starts 3-6wks after birth ```

Question 45

Meconium

Answer 45

dark green mucilaginous substance of the intestine in full term infant Consists of intestinal gland secretions and some amniotic fluid (contains IgG)

Question 46

Colostrum

Answer 46

thin milky fluid of the mammary gland produced a few days before and after parturition (contains IgA)

Question 47

Polyclonal response

Answer 47

many different antibodies derived from B cells which have recognized different epitopes on the antigen Normal B cell immune response to and antigen is polyclonal

Question 48

Monoclonal antibodies

Answer 48

antibodies derived from a single B cell clone, and that only recognize only one epitope of an antigen

Question 49

Polyclonal antibody production facts

Answer 49

``` Mixture of various B cell clones inexpensive Short process to make Produces large amounts of non-specific Ab Recognizes many epitopes on antigen Batch to batch variability ```

Question 50

Monoclonal antibody production facts

Answer 50

``` Single types of B cell clone Expensive Long process to make Produces large amounts of specific Ab Only recognizes one epitope No batch to batch variability ```