Antigens & Antibodies (6)

Properties of effective antigens

Foreign to host, chemically complex, large in molecular size, organic and degradable by the host, and carry a charge

Small molecules that are not immunogenic by themselves, but can bind B cell or T cell receptors

Haptens

When can haptens induce an immune response?

When linked to a larger protein

Example of a hapten

Penicillin

What are the antigen binding sites of immunoglobulin?

Variable region

What makes up the N termini?

Light chain and heavy chain

Where do interactions with the antigen occur?

HV3 (CDR3), HV1 (CDR1), and HV2 (CDR2)

What joins light chains?

Disulfide bonds

What are the immunoglobulin classes?

IgM, IgG, IgA, IgE, IgD

IgM specific heavy chain

mu chain

IgG specific heavy chain

gamma chain

IgA specific heavy chain

alpha chain

IgE specific heavy chain

epsilon chain

IgD specific chain

delta chain

What light chains do all classes of isotypes have?

kappa or lambda

Membrane-bound as monomer on B cell surface, but secreted as pentamer - five units linked by disulfide bonds and a J chain

IgM

First immunoglobulin to be synthesized in the primary immune response

IgM

What does IgM do?

Activates complement pathway, agglutinates particulate antigens, and can be transported into mucosal secretions

Highest concentration in serum/blood

IgG

Dominant antibody type produced in the secondary immune response

IgG

Subclasses of IgG

IgG1, IgG2, IgG3, IgG4, etc.

What does IgG do?

Activates complement (fixes) and binds to receptors on neutrophils, macrophages, and NK cells

Usually present as dimer linked by J chain

IgA

A dimer with a secretory component

Secretory IgA

Two subclasses of IgA in humans

IgA1 and IgA2

Major immunoglobulin in mucosal secretions, except in ruminants

IgA (IgG1 is predominant)

What does IgA do?

Neutralization of toxins and viruses and prevents binding of micro-organisms to host cell receptors

Immunoglobulin with very low serum concentrations in healthy animals, but higher in parasitized animals and sometimes in animals with allergies

IgE

Lacks hinge region and has extra Ch domain

IgE

What does IgE do?

Binds to Fcepsilom receptors on mast cells and basophils

What does cross-linking of bound IgE by antigen result in?

Degranulation and release of pro-inflammatory mediators from mast cells and basophils

Very low concentration in serum and primarily found with IgM on naive mature B cells

IgD

What immunoglobulin is absent in cattle and pigs and has an unknown function?

IgD

The part of an antigen to which an antibody or TCR binds

Epitope (antigenic determinant)

Most antigens have [blank] epitope(s)

Multiple

T cell epitopes are

linear peptides

B cell epitopes are usually ____________________ or _______________

Polysaccharides, peptides

Strength of interaction between epitope and one antigen-binding site

Affinity

Strength of the sum of interactions between antibody and antigen

Avidity