Antigen-Antibody Principle
PREPARED BY MR. ABHIJIT DAS
Ø Antigen =
A foreign substance (like bacteria, virus, or toxin) that enters the body
and triggers an immune response.
Ø Antibody
= A protective protein made by B-lymphocytes to neutralize or destroy
the antigen.
Ø Specific
Binding:
o Antibodies
are highly specific.
o They
bind to the exact matching antigen (like a lock and key).
Ø Immune
Complex:
o When
an antibody binds to an antigen, it forms an antigen-antibody complex.
Ø Result
of Binding:
o The
complex is then destroyed, neutralized, or removed by
immune cells.
Ø Used
in Tests:
o This
principle is used in diagnostic tests like:
§ ELISA
§ Blood
grouping
§ Widal
test
ANTIBODIES:
Immunoglobulins, also known as antibodies, serve as vital components within the body's defense mechanisms.
They're made by special cells called plasma cells, which come from another type of cell called B lymphocytes, or B cells.
These antibodies are super important because they help our body recognize and fight off pathogens like bacteria, viruses, and toxins.
STRUCTURE OF IMMUNOGLOBULINS:
1. The structure of immunoglobulins comprises a tetrapeptide framework composed of two heavy chains and two light chains, interconnected by disulfide bonds.
2. Within this structure, there exists an antigen-binding site formed at the junction between a segment of the heavy chain and a portion of the light chain.
3. This arrangement enables the specificity of antibodies, ensuring that each antibody will selectively bind to a particular antigen.
FUNCTIONS OF IMMUNOGLOBULINS:
1. Neutralization: Immunoglobulins can bind to viruses, bacteria, and toxins, preventing them from infecting cells or causing harm.
2. Opsonization: They coat pathogens, marking them for destruction by immune cells such as macrophages and neutrophils.
3. Activation of complement: Immunoglobulins can trigger the complement cascade, leading to the destruction of pathogens by forming pores in their membranes.
4. Maternal immunity: Maternal antibodies, primarily IgG, are transferred to the fetus during pregnancy and provide temporary protection against infections until the newborn's immune system matures.
5. Mucosal immunity: Immunoglobulins, particularly IgA, play a crucial role in protecting mucosal surfaces such as the respiratory, gastrointestinal, and urogenital tracts by neutralizing pathogens before they can penetrate tissues.
6. Allergic reactions: Immunoglobulin E (IgE) is involved in allergic reactions by binding to allergens and triggering the release of histamine and other inflammatory mediators from mast cells.