Clonal selection theory illustrates how immunological memory permits a rapid response upon a second exposure to an antigen

1. CLONAL SELECTION THEORY
BY
JYOTI REKHA PATRA

2. • Clonal selection theory is a scientific theory in immunology that
explains the functions of cells of the immune system (lymphocytes) in
response to specific antigens invading the body.
• The concept was introduced, in an attempt to explain the great
diversity of antibodies formed during initiation of the immune
response.
• The theory has become the widely accepted model for how the
human immune system responds to infection and how certain types
of B and T lymphocytes are selected for destruction of
specific antigens.

3. The theory states that in a pre-existing
group of lymphocytes (specifically B
cells), a specific antigen activates (i.e.
selects) only its counter-specific cell,
which then induces that particular cell
to multiply, producing
identical clones for
antibody production.
This activation occurs in secondary
lymphoid organs such as
the spleen and the lymph nodes

4. Clonal selection theory of lymphocytes:
1) A hematopoietic stem cell undergoes
differentiation and genetic rearrangement to
produce
2) immature lymphocytes with many
different antigen receptors.
3)Those that bind to antigens from the
body's own tissues are destroyed, while the
rest mature into
4) inactive lymphocytes. Most of these never
encounter a matching
5) foreign antigen, but those that do are
activated and produce
6) many clones of themselves.

5. • The clonal selection theory can be summarised with the following four
tenets:
• Each lymphocyte bears a single type of receptor with a unique specificity
(generated by V(D)J recombination).
• Receptor occupation is required for cell activation.
• The differentiated effector cells derived from an activated lymphocyte
bear receptors of identical specificity as the parent cell.
• Those lymphocytes bearing receptors for self molecules
(i.e., endogenous antigens produced within the body) are destroyed at an
early stage.

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