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Our Novel Approach: Using Cellular Immunity to Treat Established
Disease
Induction of a T cell response begins with the processing
and presentation of antigens by specialized cells of the immune
system called antigen
presenting cells (APC). The most efficient APCs in the body for
triggering T cell responses are called dendritic cells. Once protein
antigens
are taken up by dendritic cells, they are broken down into small
fragments, called peptides. These peptides are presented on the
dendritic cell surface to T cells. When T cells recognize displayed
peptides
as being foreign, they proliferate to create an “army” of
peptide-specific T cells. These activated T cells are capable of
destroying diseased cells in the body that display the same peptide
on their surface.
Cellular Immunity (Killer T Cells).
- After a pathogen is recognized
by receptors on dendritic cells, it is engulfed and its antigens
processed by the class I and class
II pathways.
- Small pieces of the antigen are displayed on the
surface of the dendritic cell bound to class I and class II
molecules, and
are recognized
by CD8+ T cells and CD4+ T cells, respectively.
- These CD4+ T
cells (T helper cells) can in turn release Type I cytokines
that help activate CD8+ T cells.
- The CD8+ T cells become activated,
and proliferate into an “army” of
antigen-specific killer T cells which then roam the body in search
of infected tissues.
Peptides are presented by dendritic cells by two routes called
the class I and class II pathways. Presentation of peptides by
the class
I and class II pathways activate CD8+ and CD4+ T cells, respectively.
CD4+ T cells, which are also known as T helper (Th) cells, are
further subdivided into Th1 and Th2 cells. Activated Th1 and Th2
cells release
molecules known as cytokines, which trigger other immune cells
to produce either a predominantly cellular (Th1 or Type I) or antibody-mediated
(Th2 or Type II) immune response. Immune responses mediated by
the
cellular side of the immune system include induction of CD8+ T
cells, also called cytotoxic T lymphocytes (CTLs) or informally, “killer
T cells.” Most importantly, these peptide-specific CTLs are
capable of recognizing and killing infected or cancerous cells,
while bypassing normal cells.
Next: Glossary of Terms
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