3 - Antibody Structure and Function Flashcards by Marian Pacho

what are the four parts of polypeptide chains

2 identical heavy chains (H)
2 identical light chains (L)

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what are the parts of polypeptide chains held together by

disulfide bonds (dashed lines)

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the two antigen binding sites are formed by what

variable (V) domains on H and L chain

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enzymatic digestion with Papain (upside down V) consist of what

two F(ab) fragments; one Fc fragment

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ezymatic digestion w/ Pepsin (<->) consist of what

one F(ab’)2 (Fab’s tied together); pieces of Fc

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what are the two activities of immunoglobulin domains

antigen binding (H+L); effector function (H only)

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intrachain disuldies form immunoglobulin fold-domains. where?

2 in L chain
4-5 in H chain

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both chains have ___ variable (V) domain and ___ constant (C) domains

one; one or more

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flexibility on immunoglobulin is provided by what

hinge region

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H chain has binding sites for what

Fc receptor and complement (effector function)

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in ig, can the antibody be membrane-bound (surface of B cell) or secreted?

YES!

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sequencing analysis of antibodies is feasible using what

antibody purified from malignantly transformed antibody-producing B cells (plasmacytes) (Plasmacytoma and multiple myeloma)

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each B malignancy produces one molecular specicies of antibody, and often excess light chain called what

Bence-Jones proteins

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sequencing reveals reveal ___ hypervariable regions of antibodies within each domain. these are also called what?

3; CDRs - complementarity determining regions

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crystallographic analysis reveals domain structure of what

antibodies

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CDRs interact w/ antigen and this does what?

determines the shape of binding site

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T/F: the shape of the binding site does not define what antigens can be bound

FALSE! it largely defines what can be bound!

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binding of CDR and antibody uses lock and key or induced fit model

induced fit - CDR is not rigid but somewhat flexible; side chains of AA are too

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what non-covalent force originates from attraction between opposite charges

electrostatic

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what non-covalent force originates from hydrogen shared between electronegative atoms

hydrogen bonds

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what non-covalent force originates from transient polarization of electron clouds oppositely polarize neighboring clouds

Van der Waals

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what non-covalent force originates from packing of hydrophobic groups to exclude water at interface. also involves van der waals forces

hydrophobic interactions

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T/F: antigens w/ similar shape may be able to bind to same antibody

TRU

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is cross reactivity advantageous or disadvantageous? examples?

both
- antibody cross reacts w/ a new strain of virus
- antibody generated against a virus that cross-reacts to self

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what is the determinant of an antigen recognized by a single antibody binding site (e.g. Fab)

epitope

what is a small molecule incapable of stimulating an immune response by itself; must be conjugated to carrier protein

Hapten

what is an antigen capable of stimulating an immune response by itself

immunogen

what is the concept used to generate vaccines

Hapten

what are the major classes of Ig/isotypes

Ig G, A, M, E, D G = 1-4 A = 1-2

are immunoglobulins named based on heavy chain

YES

T/F: both H:L chain combinations are possible, but not in the same Ig molecule

TRUE

what are the different heavy chains

mu, delta, gamma (1-5), alpha (1-2), epsilon

what are the different light chains

kappa and lambda

which ig are monomers

Ig D, G, and E

which ig is a dimer (secreted) and monomer (serum)

IgA

which ig is a pentamer

IgM

which ig contain J chains

IgA and IgM

which ig has a secretory component due to transport thru mucosal epi

IgA

what are the protective fn of antibody

1. neutralization 2. opsonization "coating" 3. complement activation

what is the prevention of bacterial, viral, or toxin adherence

neutralization

what facilitates phagocytosis and promotes antibody dependent cell-mediated cytotoxicity (ADCC)

opsonization - coating

what enhances opsonization and lyses some bacteria

complement activation

what binds Fc and IgG (preferings IgG1) bound to antigen

Fc- gamma receptors

what are examples of Fc-gamma cells

1. macrophages 2. dendritic cells 3. neutrophils 4. NK cell 5. eosinophil

what binds to Fc of free IgE (mast cells) or IgE bound to antigen (eosinophils)

Fc-episilon receptors

what are examplses of Fc-epislon cells

1. eosinophils 2. mast cell 3. basophil

have Fc receptors also been reported for IgA and IgM

yeah

do Fc receptors promote phagocytosis or antibody-dependent cell-mediated cytotoxicity (ADCC) of antaibody-coated targets

yes

IgM distribution

blood and lymphatic fluid (intravascular; too big to cross epi)

IgM serum concentrations

~1 ml/mL

IgM antigen affinity and specificity

low to moderate

key roles of IgM

1. complement activation 2. antigen aggregation and agglutination (10 antigen binding sites) 3. antibacterial activity (w/ complement)

what is the aggregation of particular antigen (e.g., RBC and bacteria) by antibodies causing clumping

agglutination

___ are carb molecuels on RBCs that may be recognized by naturally occurring antibodies causing cell clumping and lylsis

ABO blood group

compatible donor for Type A

A or O

compatible donor for Type B

B or O

compatible donor for Type AB

all, universal recipient

compatible donor for Type O

O, universal donor

distribution of IgG

blood, lymphatic fluid, tissue (intra and extravascular)

serum concentrations of ~12 mg/mL of IgG (all subclasses)

~12 mg/mL (all classes)

key roles of IgG

1. complement activation 2. neutralization 3. newbown immunity 4. activation of effetor cells vua Fc-gamma receptor bineing og antigen opsonized by IgG antibody

Protective Fc receptor (FcRp) expressed on ___ binds maternal IgG, enabling uptake, transfer, and recycling of IgG

placental cells and neonatal intestinal tissue

IgA distribution

blood and lyphatic fluid (intravascular: monomer); body secretions (tears, mucous membrane, saliva; dimer"

serum concentration of IgA

~1.8 mg/mL

antigen affinity and specificity of IgA

moderate to high

key roles of IgA

1. Neutralization (toxins, bacteria, virus), particularly along mucosal surfaces 2. Antigen aggregation and agglutination (secretory IgA is dimeric, therefore it has 4 antigen binding sites)

___ bind to ligands on bacterial toxins, viruses or bacteria responsible for cell adhesion and entry

IgA or IgG

can antibody binding inhibit liagand-receptor interaction, preventing adhesion to cell

yesah

nautralizing activity can be transferred; forms basis of anti-venoms called what

passive immunization

IgE distribution

bound to high affinity Fc-epsilon expressed on mast cells, basophils, and eosinophils

IgE serum concentrations

~2 x 10^-5 mg/Ml

antigen affinity and speficitiy of IgE

moderate to high

key roles of IgE

Defense against large parasites (eosinophil ADCC, basophil and mast cell degranulation) Allergic responses (basophil and mast cell degranulation)

T/F: IgE is free in serum and not Fc-episolon r1

FALSE - IgE is bound to Fc-episoln R1 and not free in serum

antigen binding by IgE:Fc-epsilonR1 on. mast cells or basophils trigger what

degranulation and inflammation

distribution of IgD

surface of B cells

serum concentration of IgD

~0.04 mg/mL

antigen affinity and specificity of IgD

low to moderate

what are the key roles of IgD

Marker for differentiation (only on mature B cells) Regulation of tolerance (mice lacking IgD have more self-reactive B cells)

secreted IgA is mostly produced where

salivary glands (70% major glands, 30% minor glands)

Ig___ and Ig___ is mostly produced from gingival crvide

G and M

Ig___ increases in periodontal disease

following immmunization, what is produced first, then what class follows?

IgM produced first, then class switching to IgG and other isotypes

T/F: the first response in immunization is faster, contains higher affinity antibodies largerly switch to IgG, and has longer duration

FALSE! the sceondary response

what has an anamnestic (memory) response

IgG