Question

Biochemistry Tutorial: Immunoglobulins & The Immune Response

Answer 1

\({\bf{Basics~of~Immunity:}}\)
immune response: capacity to generate antibodies in response to antigens
- carried out by leukyocytes (macrophates + lymphocytes)

two types: humoral immune system (directed @ bacteria infections, viruses)
cellular immune system (directed at host cells that have been infected, parasites)

- antibodies/immunoglobulins: agents that carry out the humoral immune response. bind bacteria, viruses, etc., identify them, target them for destruction. produced by B-lymphocytes
- a typical binding site for an immunoglobin is a cleft lined w/ amino acid residues, rather than a prosthetic group as with myoglobin/hemoglobin

- cellular immune response is governed by cytotoxic T-cells. receptors recognize and bind ligands
- helper T-cells produce cytokines and stimulate production of cytotoxic T cells and B cells (clonal selection)

Answer 2

cont.
antigen elicits an immune response
- epitope: the specific chemical group on antigen that binds to antibody
- haptens: small molecules that can be linked to large molecule to elicit immune response



personally we don't really have to memorize these (this is more of a physiology/anatomy topic) but just in case you need a refresher

Answer 3

\({\bf{Immunoglobulin~Structure:}}\)

IgG is the most abundant, major Immunoglobulin class
- 2 heavy chains + 2 light chains
- linked by noncovalent + disulfide bonds
- composed of variable domains and constant domains


Fc is the "base" fragment and Fab are the two forked off antigen binding fragments

constant domains have immunoglobulin fold (3 per heavy chain, 1 per light chain)

variable domains make up the antigen binding sites at the ends of the "fork"

Answer 4

\({\bf{Other~Immunoglobulins:}}\)
IgA --> heavy chain alpha
IgD --> heavy chain delta
IgE --> heavy chain epsilon
IgG --> heavy chain gamma
IgM --> heavy chain mu
toolazytotypeintheletterswhee

each has light chains kappa and lambda

IgM is monomeric or cross-liked pentameter. first one produced in immune response.
IgA is monomer/dimer/trimer
IgD and E are similar to G in structure
IgG is principal agent of secondary immune response --> Fc region binds to antigen + activates leukocytes that bind and engulf invader

Answer 5

\({\bf{Antibody~Binding:}}\) is
- specific (because of specific AA residues in variable domains)
- complementary between antigen and binding site
- strong (low Kd)
- induced (conformational changes between the antibody and antigen upon binding)

Answer 6

\({\bf{Analytical~Techniques:}}\) are made possible through
polyclonal antibodies: antibodies produced by diff. B-lymphocytes in response to antigen, where different antibodies can respond to diff. parts of the antigen
monoclonal antibodies: antibodies produced by identical B-cells

will be covering: ELISA, Western blotting (sometimes called immunoblotting)

\({\bf{ELISA:}}\)



stands for enzyme-linked protein assay
basic steps
- adsorb proteins to plate
- wash with cheap protein like casein to block unoccupied sites
- treat with primary antibody (binds to the protein being studied)
- wash away unbound antibody
- treat with secondary antibody
- linked to enzyme to create product w/ color
- wash away secondary antibody
- add substrate of antibody-linked enzyme
- measure intensity of color, as proportional to protein concentration

\({\bf{Western~Blotting:}}\)
- separate protein w/ gel electrophoresis
- transfer to nitrocellulose membrane
- block unoccupied cells
- treat w/ primary antibody + secondary antibody + substrate
- synthesizes colored precipitate where the protein of interest is concentrated

Answer 7

Source material is section 5.2 of Principles of Biochemistry 7th edition by Nelson, David L., and Cox, Michael M.