Biomedical Engineering Reference
In-Depth Information
unless antibody effector functions are activated. One effector function
is the activation of complement, which is activated by some antibody
isotypes. Complement is name for a number of serum proteins that
can destroy invading pathogens by lysing them. Complement causes
lysis by the insertion of proteins into the membrane which form pores,
thereby causing the loss of cellular integrity. Complement activation also
results in the production of chemoattractants, which are small bioactive
cleavage products of the complement cascade whose production elicits
the accumulation of specific white blood cells (including macrophages
and neutrophils) that engulf and destroy pathogens. Certain antibody
classes can cross the placenta to protect the fetus, or cross the ep-
ithelial layers to get into secretions to fight pathogens before they enter
sterile spaces of the body. The constant region domains of some anti-
bodies are bound by cellular receptors on phagocytic cells after antibody
binding to pathogens, which causes the uptake and destruction of the
pathogens. Antibodies are also responsible for our allergies, but this
same antibody class (IgE) also helps destroy parasites.
Each antibody isotype is an oligomeric glycoprotein composed of two
heavy chains and two light chains (two classes, IgM and IgA, can be
multimers of these), with differences in the heavy chains specifying the
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