636
UNIT FOUR
TABLE
16.8
|
Actions of Antibodies
General Action
Type of EF
ect
Description
Direct Attack
Agglutination
Antigens clump
Precipitation
Antigens become insoluble
Neutralization
Antigens lose toxic properties
Activation of Complement
(Antibodies combined with antigens)
Opsonization
Alters antigen cell membranes so cells are more susceptible to phagocytosis
Chemotaxis
Attracts macrophages and neutrophils into the region
Agglutination
Clumping of antigen-bearing cells
Lysis
Allows rapid movement of water and ions into the foreign cell causing osmotic rupture of the foreign cell
Neutralization
Altering the molecular structure of viruses, making them harmless
Localized Changes
InF
ammation
Helps prevent the spread of antigens
A
t the turn of the last century, German bac-
teriologist Paul Ehrlich developed the con-
cept of the “magic bullet”—a substance
that could enter the body and destroy diseased
cells, yet spare the healthy ones. The biochemicals
and cells of the immune system, with their great
specificity for attacking foreign tissue, would be
ideal magic bullets.
Immunotherapy
uses immune
system components to fight disease—both the
humoral immune response (antibodies) and the
cellular immune response (cytokines).
Monoclonal Antibodies
Tapping the speci±
city of a single B cell and using
its single type, or
monoclonal,
antibody to target
a speci±
c antigen (such as on a cancer or bacte-
rial cell) awaited ±
nding a way to entice the nor-
mally short-lived mature B cells into persisting in
culture. In 1975, British researchers Cesar Milstein
and Georges Köhler devised
monoclonal antibody
(MAb) technology to capture the antibody-mak-
ing capacity of a single B cell.
Milstein and Köhler injected a mouse with
antigen-laden red blood cells from a sheep. They
then isolated a single B cell from the mouse’s spleen
and fused it with a cancerous white blood cell from
a mouse. The result was a fused cell, or
hybridoma,
with a valuable pair of talents: Like the B cell, it pro-
duces large amounts of a single antibody type; like
the cancer cell, it divides continuously (fig. 16A).
Human versions of MAbs are now used.
MAbs are important in basic research, vet-
erinary and human health care, and agriculture.
Cell biologists use pure antibodies to local-
ize and isolate proteins. Diagnostic MAb “kits”
detect tiny amounts of a single molecule. Most
kits consist of a paper strip impregnated with
a MAb, to which the user adds a body F
uid. ²or
example, a woman who suspects she is preg-
nant places drops of her urine onto the paper. A
color change ensues if the MAb binds to human
16.1
FROM SCIENCE TO TECHNOLOGY
Immunotherapy
FIGURE 16A
Monoclonal antibodies are produced by a type of arti±
cial cell combination
called a hybridoma. It consists of a cancer cell (the F
at blue cell) fused with a B cell (the round
green cell). The cancer cell contributes rapid and continuous division; the B cell secretes a single
antibody type (7,000×).
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