Page 542 - 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 C H mebooksfree.com mebooksfree.com
60
T
R
A
P
E

Humoral Immunity

mebooksfree.com mebooksfree.com mebooksfree.com Function of Antibodies mebooksfree.com mebooksfree.com
mebooksfree.com

CHAPTER C ONTENT S

Introduction
Antibodies in the Fetus
The Primary Response
Tests for Evaluation of Humoral Immunity
The Secondary Response
Self-Assessment Questions
Response to Multiple Antigens Administered
Simultaneously
Practice Questions: USMLE & Course Examinations
mebooksfree.com
mebooksfree.com mebooksfree.com mebooksfree.com afforded by a vaccine the first time it is given is delayed mebooksfree.com
mebooksfree.com
INTRODUCTION
compared with the protection afforded by a booster shot in
Humoral (antibody-mediated) immunity is directed
which a faster secondary response occurs.
primarily against (1) exotoxin-mediated diseases such as
The lag period of the primary response is typically 7 to
tetanus and diphtheria, (2) infections in which virulence is
10 days but can be longer depending on the nature and
related to polysaccharide capsules (e.g., pneumococci,
dose of the antigen and the route of administration (e.g.,
meningococci, Haemophilus influenzae), and (3) certain
parenteral or oral). A small clone of B cells and plasma cells
viral infections. In this chapter, the kinetics of antibody
synthesis (i.e., the primary and secondary responses) are
concentration continues to rise for several weeks, then
described. The functions of the various immunoglobulins
declines and may drop to very low levels (Figure 60–1). The
are summarized in this chapter and are described in detail specific for the antigen is formed. The serum antibody
first antibodies to appear in the primary response are IgM,
mebooksfree.com
mebooksfree.com mebooksfree.com mebooksfree.com THE SECONDARY RESPONSE mebooksfree.com
mebooksfree.com
in Chapter 59.
followed by IgG or IgA. IgM levels decline earlier than IgG
levels.
THE PRIMARY RESPONSE
The primary response occurs the first time that antigen is
When there is a second encounter with the same antigen or
encountered. In the primary response, antibodies are
a closely related (or cross-reacting) one, months or years
detectable in the serum after a longer lag period than
after the primary response, there is a rapid antibody
occurs in the secondary response (see Table 60-1). This
response (the lag period is typically only 3–5 days) to
concept is medically important because the protection
TABLE 60-1 Important Features of the Primary and Secondary Antibody Response
Feature
Secondary Response
Primary Response
mebooksfree.com mebooksfree.com mebooksfree.com mebooksfree.com mebooksfree.com mebooksfree.com
3–5 days
7–10 days
Lag period before antibodies detected
IgM
IgG
Main antibody type produced
Relatively small
Amount of antibody produced
Relatively large
Duration of antibody response
Long
Short
No
Affinity maturation occurs
Yes
531
mebooksfree.com mebooksfree.com mebooksfree.com mebooksfree.com mebooksfree.com mebooksfree.com