Immunoglobulins

produce antibodies

what is the function of plasma cells?

bone marrow and secondary follicles

where are plasma cells located?

die after several days

what is the life span of plasma cells?

glycoproteins

what are immunoglobulins also known as?

humoral immunity

what immunity do immunoglobulins participate in?

extracellular pathogens

what is humoral immunity effective against?

• IgG

• IgM

• IgA

• IgD

• IgE

what are some common classes of immunoglobulins?

<80%

what percent of serum quantity is IgG?

<15%

what percent of serum quantity is IgA?

<5%

what percent of serum quantity is IgM?

<0.2%

what percent of serum quantity is IgD?

trace amounts

how much of serum is IgE?

gamma globulin

what is the most antibody in gamma band when serum is elecrophoresed?

a monomer

what is the basic unit of antibodies?

four

how many polypeptides comprise a basic structure of an antibody?

• 2 heavy chains

• 2 light chains

what are the four polypeptides comprising a basic antibody?

IgG

what is an example of an antibody with a basic structure?

paratope

what is also known as the antigen binding site?

epitopes

what do paratopes bind to?

3

how many pieces comprises papain?

• 2 Fab fragments

• 1 Fc

what are the pieces comprising papain?

two pieces of heavy chain which crystallizes at 4℃

what is Fc?

• opsonization

• complement fixation

what are the important effector functions of antibodies?

• 1 heavy chain

• 1 light chain

what comprises Fab?

disulfide bond

what type of bond occurs in Fab?

antigen-binding

what capacity does Fab have?

binding of Fc portions of the antibody to the Fc receptors on phagoctes

what is opsonization?

• F (ab)₂

• Fc’

what are the components of pepsin?

antigen binding fragment

what is F(ab)₂?

smaller than Fc

what is Fc’?

constant region

what are light chain types based on?

• Kappa

• lambda

what are the types of light chains?

2:1

what is the ratio of Kappa to Lambda in light chains?

only one

how many types of light chains can each Ig molecule have?

variable and constant regions

what are Bence Jones proteins based on?

malignant plasma cells

how are Bence Jones proteins produced in excess?

in the urine of multiple myeloma patients

where are Bence Jones proteins primarily found?

constant regions

what are classes and subclasses of heavy chains determined by?

Ch1, Ch2, Ch3

which constant regions determine class/subclass of heavy chains?

• G (γ)

• M (µ)

• A (⍺)

• D (δ)

• E (ε)

what are the classes of heavy chains?

• IgG1

• IgG2

• IgG3

• IgG4

what are the subclasses of G(γ) heavy chains?

• IgA1

• IgA2

what are the subclasses of A (⍺) heavy chains?

isotype immunoglobulin determinant

what refers to constant region of heavy chain?

• Ch

• Cl

where are isotype immunoglobulin determinants located?

all variants in normal persons

how often do isotype determinants occur?

• quantify Ig classes and subclasses

• characterize B cell leukemia

• help with immunodeficiencies diagnosis

what are the uses of the isotype determinant?

ELISA and Western Blot

what are some example of tests used to quantify Ig classes and subclasses?

allotype determinant

what occurs mainly in constant region of antibodies?

mainly Ch and Cl—Gm groups in humans

where are allotype determinants located?

allelic variants between individuals within a species

how often do allotype determinants occur?

idiotype determinant

what occurs in the variable region of antibodies?

variable regions

where are idiotype determinants located?

specific to each individual immunoglobulin molecule

how often do idiotype determinants occur?

heavy chain between Ch1 and Ch2

what is the hinge region?

very flexible

what is a characteristic of the hinge region?

independently

how do antigen-binding sites work in the hinge region?

a carbohydrate

what is Ch2?

Ch2 domain

where is Ch2 located?

helps Fc receptors on phagocytes recognize Fc unit

what is the function of Ch2?

complement binding site

what type of binding site is Ch2?

• antibody blocks binding of microbe and infection of cell

• antibody blocks binding of toxin to cell receptor

• antibody blocks infection of adjacent cell

how do antibodies neutralize pathogens?

antibodies coat microbes and promote their ingestion by phagocytes

how do antibodies opsonize?

antibody dependent cell cytotoxicity

what does ADCC stand for?

NK cells and other WBCs

which cells function in ADCC?

lysis of microbes and host cells

what does activation of complement result in?

• heavy chain

• predominant Ig

• longest half life—23-25 days

• MW= 150,000

what are some characteristics of IgG?

• provides immunity for newborn by crossing the placenta

• fixes complement

• opsonizes antigen for enhanced phagocytosis

• neutralize toxins and viruses

• antibody-dependent cell cytotoxicity by WBCs

• in the lab

  • participate in agglutination and precipitation reactions

what are the functions of IgG?

IgG2

which IgG subset is least efficient at providing immunity for newborns?

IgG3

which IgG subset is most efficient at fixing complement?

IgG2, IgG4

which IgG subsets are poor mediators of complement fixation?

it is larger

why is IgM better at agglutination than IgG?

precipitation

what reaction is IgG better at than agglutination?

• heavy chain

• macroglobulin

• MW = 900,000

• ~10% of serum Ig

• half life = 10 days

what are some characteristics of IgM?

pentamer

what is the structure of IgM?

5 subunits (monomers) in serum

what is pentamer structure of IgM?

2 heavy and 2 light chains

what does each subunit in a pentamer have?

monomer

what forms on B cell surface?

J chain

what is included in the IgM structure?

glycoprotein link subunits

what is a J chain?

10

how many antigen binding sites does IgM have?

low

what affinity does IgM have?

• intravascular pool and not in body fluids or tissue

• cannot cross the placenta

where is IgM located?

• primary antibody response

• BCR for antigen on mature B cell

• agglutination

• fixes complement

what are some IgM functions?

as long as antigen is present

how long does IgM synthesize during the primary antibody response?

no

does IgM have memory cells?

potent bacterial defense mechanism

what is a product of IgM agglutination?

you only need one immunoglobulin due to its size and conformational changes

why is IgM the best immunoglobulin for triggering classical complement?

mainly in MALT

where is IgA produced?

sub-epithelia tissues

where are IgA secreting plasma cells found?

alpha

what is the heavy chain of IgA?

IgA1

what subclass of IgA is found in serum?

monomer

what is the structure of IgA1?

dimer

what is the structure of IgA2?

mucosal surfaces and body secretions

where is IgA2 found on?

• 2 monomers + J chain

• secretory component

what is the dimer structure of IgA2 comprised of?

epithelial cell

where are secretory component precursors?

binds and transports dimer across the epithelial barrier to mucosal surfaces

what is the function of secretory component precursors?

facilitates transport of IgA to mucosal surfaces and makes dimer more resistant to enzymatic digestion

what is the function of secretory component?

protects mucosal surfaces by neutralization and opsonization/complement activation

what is the function of IgA?

neutralization

what is the major role of IgA?