Page 512 - Review of Medical Microbiology and Immunology ( PDFDrive )

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CHAPTER 58 Cellular Basis of the Immune Response
501
(CD8-positive)
Thymus
target cells

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IL-2

Helper T cell
(CD4-positive)
Delayed hypersensitivity
Bone marrow
stem cell

IL-4, IL-5
Antibodies
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(bone marrow
Plasma cell
in humans)
FIGURE 58–1
Origin of T and B cells. Stem cells in the bone marrow (or fetal liver) are the precursors of both T and B lymphocytes. Stem
cells differentiate into T cells in the thymus, whereas they differentiate into B cells in the bone marrow. Within the thymus, T cells become either
CD4-positive (helper) cells or CD8-positive (cytotoxic) cells. B cells can differentiate into plasma cells that produce large amounts of antibodies
(immunoglobulins). Dotted lines indicate interactions mediated by interleukins. (Reproduced with permission from Brooks GF et al. Medical Microbiology.
20th ed. Originally published by Appleton & Lange. Copyright 1995 McGraw-Hill.)

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TABLE 58–1 Comparison of T Cells and B Cells
T Cells
B Cells
Feature
Yes
Yes
Antigen receptors on surface
Yes
No
Antigen receptor recognizes only processed peptides in association with MHC protein
No
Antigen receptor recognizes whole, unprocessed proteins and has no requirement for
Yes
presentation by MHC protein
IgM on surface
Yes
No
CD3 proteins on surface
Clonal expansion after contact with specific antigen
Yes
Yes
Yes
No
Immunoglobulin synthesis Yes No
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No
Yes
Regulator of antibody synthesis
IL-2, IL-4, IL-5, and gamma interferon synthesis
Yes
No
Effector of cell-mediated immunity
No
Yes
Yes
No
Maturation in thymus
Yes
No
Maturation in bone marrow
IgM = immunoglobulin M; IL = interleukin; MHC = major histocompatibility complex.
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