C H A P T E R 3 5 , F I G U R E 4
Microbe destruction by neutrophils and antibody-dependent, cell-mediated cytotoxic-
ity. (A) Neutrophils recognize and attack antibody-tagged microorgansims by a mechanism called antibody-depen-
dent, cell-mediated cytotoxicity (ADCC). In this defense mechansim, microbes “tagged” by antibodies are destroyed
by a respiratory burst of 0 3", H20 2, and NO produced by the attacking neutrophils. (B) In a similar way, natural killer
(NK) cells recognize antibody-tagged virus-infected cells and tumor cells.
C H A P T E R 3 5 , F I G U R E 5
Structural motif of the immunoglobulin
family. Each domain of the immunoglobulin or other molecule of the
immunoglobulin family is composed of a collection of p strands that
form a globular structure. Colors indicate different p strands. There are
seven strands in the constant region domains that form two p sheets; one
sheet contains three antiparallel strands and the other four antiparallel
strands. The orientation illustrates the two sheets that together create the
P sandwich or immunoglobulin fold.
C H A P T E R 3 5 , F IG U R E 6
Pairs of immunoglobulin motif structures
(see Figure 35-7) connected by a “tether” polypeptide that creates a flexible
fold. The disulfide bridges that connect the P sheets of the p sandwich are
shown as yellow space-filling residues. Each IgG molecule contains six such
folds arranged so that a heavy and light chain folds partially wrap around
each other (Figure 35-7 B, C). The ribbon model shown is from an x-ray
crystallographic structure of a Fab fragment. The figure is derived from the
coordinates published in the Protein Data Bank file, 2FPB.
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