Epitope

Specific part of antigen to which antibody binds

What type is antibody-antigen bonding?

non-covalent: van der waals, hydrophobic, ionic

Hapten

a small molecule or portion of a molecule that, bu itself, cannot induce an immune response.  must be part of a larger carrier molecule

basic structural unit for monomeric antibody

4 chains (2 identical heavy, 2 identical light), which are interconnected thru disulfide bonds.  Only technically has tertiary structure because subunits are held together non-covalently.

immunoglobulin fold

antiparallel beta sheets stabilized by disulfide bonds

Constant region

C_H, C_L. Carboxyl-terminal region of H and L chanins that is identical within each antibody isotype.

Variable region

V_H, V_L. Region responsible for antibody specificity. Humans capable of producing 10⁸ different determinants for epitope binding.

Hypervariable region

sub-region in the variable region which is primarily responsible for specificity.  AKA complimentarity-determining region (CDR)

CDR

complimentarity-determining region,

 the hypervariable region of heavy and light chains responsible for antibody specificity

C-terminal location in antibody structure

constant region

C1q

helps with antigen elimination

N-terminal location in antibody structure

2 (identical) variable regions

Hinge region (location and function)

Area between C_H1 and C_H2, can swivel to accomodate different conformations

H chain domains

V_H, C_H1-3

Domains of light chain

C_L, V_L

Location of disulfide bonds in antibody structure

within each constant domain, between C_L and C_H1 domains, in hinge region (2) between C_H1 and C_H2

Location of carbohydrate residue in antibody

between constant heavy-chain regions

neutralization

phagocyte elimination

opsonization

antibodies coat antigen with C3b-->phagocytosed

complement fixation

antibody-antigen binding-->conf change--> C1q exposed-->series of enzymes, amplification of response-->cascade-->lysis of antigen (complex inserted into cell wall)

opsonin

old term for proteins that signal phagocytosis by neutrophils and macrophages

C3b

major opsonin, binds specific receptors on macrophage surface

C3 deficiency

repeat bacterial infections

ex: C3b is an important opsonin, whcih binds receptors on macrophage cell surface

monomeric Ig's

serum: IgD, IgE, IgG, IgA

A-G-E-D

dimeric Ig's

IgA's of seromucosal secretions

pentameric Ig's

IgM (in serum)

IgG

most abundant antibody (75% of serum ab's)

ONLY one that transverses placenta to protect fetus

4 γ H chain isotypes (H_1-4)

monomeric

light chain isotypes

κ or λ

heavy chain isotypes

gamma 1-4, mu, alpha 1-2, epsilon, delta

IgA

early defense, loc in resp/GI tract mucosal membranes (found in tears, saliva, mucosal secretions)

alpha H chain isotype

2 subtypes: IgA₁ and IgA₂

monomer, dimer (J chain) or dimer plus secretory (SP)

J chain

holds together IgA dimer or IgM pentamer

SP

secretory piece, IgA dimer plus secretory piece (most common form of IgA) facilitates movement across mucosal layers

IgM

mu H isotype

first antibody made by a B cell in humoral response against virus/bacteria (presents on cell surface)

8-10% of adult antibodies

PRODUCED BY FETUS

monomeric form (on B cell surface), soluble pentamer (in serum) held together by J chain/disulfide bonds

When is the IgM pentamer formed?

only after antigen and/or cytokine activation of the B cell

Affinity of the epitope binding sites of pentameric IgM

only 5 of the 10 are high affinity

Which Ig is the primary means of eliminating carbohydrate antigens?

IgM

Which Ig is made the fastest?

IgM

IgE

epsilon H chain isotype

primary antibody of mucosal membranes and against intestinal parasites

antigen binding induces allergic reaction, release of histadines and vasoactive amines by mast cell and basophils

monomeric

4 constant H domains

Where is IgE found?

mucosal membranes of lungs/GI tract, tonsils, adenoids, spleen

found only in trace amounts in serum

IgD

presented on B cell surface

serum

function unknown

monomeric

delta H chain isotype

Ig reaction to immunization

IgM peaks first, several weeks until IgG built up

Multiple myeloma

cancer of the immune system, 1 class or specificity of antigen increases production without an antigen being present