Page 516 - Review of Medical Microbiology and Immunology ( PDFDrive )

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mebooksfree.com mebooksfree.com mebooksfree.com CHAPTER 58 Cellular Basis of the Immune Response 505 mebooksfree.com
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Microorganisms

Macrophage
*
See legend
*
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IL-12
Naïve

T cell
(Th-0)
IL-12-
induced
pathway
IL-4-
induced

cell
cell
Gamma Th-1 IL-2 Th-2 IL-4
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interferon
IL-5
Activated
B
Plasma
Activated
cytotoxic
cell
cell
Antibody-mediated immunity
Cell-mediated immunity
FIGURE 58–3
The origin of Th-1 and Th-2 cells. On the left side, the origin of Th-1 cells is depicted. Microorganisms are ingested by mac-
rophages, and interleukin (IL)-12 is produced. IL-12 induces naïve Th-0 cells to become Th-1 cells that produce gamma interferon and IL-2. These
interleukins activate macrophages and cytotoxic T cells, respectively, and cell-mediated immunity occurs. On the right side, the origin of Th-2
cells is depicted. Microorganisms are ingested by an unknown type of cell (see footnote below), and IL-4 is produced. IL-4 induces naïve Th-0
cells to become Th-2 cells that produce IL-4 and IL-5. These interleukins activate B cells to become plasma cells, and antibodies are produced.
Not shown is the differentiation of Th-17 cells from naïve helper T cells (Th-0) under the direction of IL-6 and TGF-β produced by dendritic cells.
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Also not shown in the figure is an important regulatory step, namely, that IL-10 produced by Th-2 cells inhibits IL-12 production by macro-
phages and drives the system toward an antibody response and away from a cell-mediated response. *The human cell that produces the IL-4,
which induces naïve helper T cells to become Th-2 cells, has not been identified.

TABLE 58–4 Comparison of Th-1 Cells and
Th-1 or Th-2 cells is unknown.
Th-2 Cells
How the appropriate response is stimulated is known for
Property
Th-1 Cells
Th-2 Cells
one medically important organism, namely, M. tuberculosis.
A lipoprotein of that bacterium interacts with a specific
No
Produces IL-2 and gamma interferon
Yes
Toll-like receptor on the surface of the macrophage, which
Produces IL-4, IL-5, IL-6, and IL-10
No
Yes
induces the production of IL-12 by the macrophage. IL-12
Enhances cell-mediated immunity and
No
Yes
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delayed hypersensitivity primarily
Th-1 type of helper T cells that are required to mount a
Yes
Enhances antibody production
No
cell-mediated (delayed hypersensitivity) response against
primarily
the organism.
Yes
No
Stimulated by IL-12
A subset of CD4 cells called Th-17 cells play an impor-
No
Yes
Stimulated by IL-4
tant role in mucosal immunity, especially in the mucosa of
the gastrointestinal (GI) tract. These cells are characterized
IL = interleukin.
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