Page 533 - Review of Medical Microbiology and Immunology ( PDFDrive )

mebooksfree.com

mebooksfree.com
mebooksfree.com
mebooksfree.com
mebooksfree.com
mebooksfree.com
mebooksfree.com mebooksfree.com mebooksfree.com mebooksfree.com H A mebooksfree.com mebooksfree.com
59
T
P
C
R
E

Antibodies

mebooksfree.com
mebooksfree.com mebooksfree.com mebooksfree.com Isotypes, Allotypes, & Idiotypes mebooksfree.com mebooksfree.com

CHAPTER C ONTENT S

Introduction
Immunoglobulin Genes
Monoclonal Antibodies
Immunoglobulin Class Switching (Isotype Switching)
Immunoglobulin Structure
Allelic Exclusion
Immunoglobulin Classes
Catalytic Antibody
IgG
Self-Assessment Questions
IgA
IgM
mebooksfree.com
mebooksfree.com mebooksfree.com mebooksfree.com Practice Questions: USMLE & Course Examinations mebooksfree.com
mebooksfree.com
IgD
IgE

1
INTRODUCTION
(e.g., in a plasma cell tumor [myeloma]) are homogeneous
(i.e., they are monoclonal).
Antibodies are globulin proteins (immunoglobulins [Ig])
Monoclonal antibodies also can be made in the labora-
that react specifically with the antigen that stimulated their
production. They make up about 20% of the protein in
cell (Figure 59–1; also see box “Hybridomas & Monoclonal
blood plasma. Blood contains three types of globulins,
Antibodies”). Such hybridomas produce virtually unlim-
alpha, beta, and gamma, based on their electrophoretic tory by fusing a myeloma cell with an antibody-producing
ited quantities of monoclonal antibodies that are useful in
mebooksfree.com
mebooksfree.com
mebooksfree.com mebooksfree.com mebooksfree.com IMMUNOGLOBULIN STRUCTURE mebooksfree.com
migration rate. Antibodies are gamma globulins. There are
diagnostic tests and in research (see box “Hybridomas &
five classes of antibodies: IgG, IgM, IgA, IgD, and IgE. Anti-
Monoclonal Antibodies”).
bodies are subdivided into these five classes based on dif-
ferences in their heavy chains.
The most important functions of antibodies are to neu-
tralize toxins and viruses, to opsonize microbes so they
Immunoglobulins are glycoproteins made up of light (L)
are more easily phagocytosed, to activate complement,
and heavy (H) polypeptide chains. The terms light and
and to prevent the attachment of microbes to mucosal
heavy refer to molecular weight; light chains have a molec-
surfaces. The specific antibody classes that mediate these
ular weight of about 25,000, whereas heavy chains have a
functions are described in Table 59–1. In addition to these
functions, antibodies have a catalytic (enzymatic) capa-
body molecule has a Y shape (Figure 59–2) and consists of
bility that is described in a separate section at the end of
four polypeptide chains: two H chains and two L chains.
this chapter. molecular weight of 50,000 to 70,000. The simplest anti-
mebooksfree.com mebooksfree.com mebooksfree.com produce the same type of immunoglobulin molecule, which indicates mebooksfree.com
mebooksfree.com
mebooksfree.com
1
Multiple myeloma is a malignant disease characterized by an over-
MONOCLONAL ANTIBODIES
production of plasma cells (B cells). All the myeloma cells in a patient
Antibodies that arise in an animal in response to typical
that all the cells arose from a single progenitor. Excess κ or λ L chains
are synthesized and appear as dimers in the urine. These are known as
antigens are heterogeneous, because they are formed by
Bence Jones proteins and have the unusual attribute of precipitating at
several different clones of plasma cells (i.e., they are poly-
50°C to 60°C but dissolving when the temperature is raised to the
clonal). Antibodies that arise from a single clone of cells
boiling point.
522
mebooksfree.com mebooksfree.com mebooksfree.com mebooksfree.com mebooksfree.com mebooksfree.com