2. Objectives
• By the end of this presentation, you should be
able to:
Define antibody and terms related to it
Mention types of antibodies as used in
Immunohistochemistry
Explain how antibodies are produced in the
body
Describe production of antibodies for
laboratory use
3. Intro…
• Antibody is a molecule produced in response
to an antigen.
• They are protein which are produced when a
foreign organisms challenges the body
• It as the property of combining with the
antigen that induced its formation.
• Antibodies have four important properties;
specificity, sensitivity, affinity and avidity.
4. Cont..
• Affinity is the three dimensional fit of the
antibody to its specific antigen and is a
measure of the binding strength between an
antigenic epitope and its specific antibody
combining site.
• It is synonymous to the lock and key
hypothesis of enzyme whereby an antigen is a
lock and antibody is a key and a key which fit
into the lock has more affinity
5. Cont…
• Avidity is a property referring to the
heterogeneity of the antiserum which will
contain various antibodies reacting with different
epitope on the same antigen molecule.
• A specific but multivalent antibody is less likely to
be removed by the washing processes than a
monovalent antibody.
• Avidity therefore is the functional combining
strength of an antibody with its antigen.
6. Cont…
• Sensitivity is the relative amount of antigen that
an immunocytochemical/histochemical
technique is able to detect.
• A technique with high sensitivity is able to detect
smaller amounts of antigen than a technique with
low sensitivity.
• If used to detect the same amount of antigen, the
technique with high sensitivity would produce a
larger signal than a method with low sensitivity.
7. Cont…
• Antibody specificity is the characteristics of an
antibody to bind selectively to a single epitope
on an antigen.
• Antigen can have multiple epitopic site but a
specific antibody is capable of recognizing
only one site.
• Antibody with a high specificity are used
commonly in treatments and for tumor
differentiation.
8. Types of antibodies
• Antibodies are of different types depending
on the use, method of production or source of
production
• Depending on the use in IHC, antibody can be
classified as primary or secondary
• Primary antibody is the antibody which bind
directly to the epitopic site of antigen interest.
9. Cont..
• Primary antibodies are raised against the
antigen of interest and they can either be
labeled or unlabeled.
• Secondary antibodies are those which are
raised against immunoglobulins of another
animals
• When immunoglobulin from rabbit are
injected into mouse, mouse will produce anti-
immunoglobulin against the rabbit proteins.
10. Cont…
• Secondary antibodies must be produced in
animal species different from that which
produced the primary antibody.
• Antibodies are also called markers in sense
that they are used to localize the site of
antigen in the tissue.
• Markers are either predictive or prognostic
markers.
11. Cont…
• Predictive markers
• Pathological tests that indicate the likely
response of the disease to a specific type of
therapy.
• They are used to direct treatment; examples
are oestrogen receptors, progesterone
receptors and human endothelial growth
factor receptor 2
12. Cont…
• Prognostic markers
• Pathological tests that indicate the likely short
and long term outcome for a patient with a
particular disease.
• They indicate the likely outcome of the patient
treatment and survival chances of the certain
diseases.
13. Antibody production
• In human body humoral response produces
plasma cells
• Introduction of antigen causes the progenitor
cells to produce multiple B-cells lineages
• Each lineages produces specific antibody
combining sites but all raised against the same
antigen.
• Clonal selection occurs in the bone marrow
14. Cont…
• In a normal immune response, an antigen
triggers multiple B-cell lineages, each with
differing antibody combining specificities,
through a process called clonal selection.
• Further refinement in the B-cell selection
process continues in the periphery.
15. Cont..
• The benefit of the normal immune response is
that multiple clonal lineages of B-cells, each
with its unique specificity but targeting the
same antigen, are simultaneously stimulated
to differentiate into plasma cells or memory
cells over a period of four to five days
• The result is a variety of antibodies specific for
the antigen in the form of a combined
polyclonal antibody response.
