470
JOHN E. CUSHING
Jones proteins and other Ig fragments produced by individuals with
pathological defects ) are leading to a profound understanding of the
subunit structure of these molecules. Both are composed of four chains
of polypeptides, one pair of shorter, “light” ( L ) chains and one pair
of longer, “heavy” ( H ) chains. These chains are relatively similar in
both molecules, the major contrasts between ,G and ,M bcing that
while ,G is a single molecular entity with two combining sites pc’r antibody the ,M molecule consists of ;I complex of five repeating molecular
entities, each grossly similar to a ,G molecule with a total combining
valence of ten. The y M molecule is readily inactivated by mercaptoethanol, where:is the ,
C nioleculc is not, a simple but far from comprehensive example of a contrasting characteristic of the molecules. An
individual serum has all four classes of Ig in variable amounts dcpending upon physiological conditions such as location and length of
immunization.
When the L and H chains of ,G are separated from each other,
they are found to be polypeptides consisting of from 210 to 220 amino
acid residues for the L chains, and around 440 for the H chains. Injection of separate chains into rabbits produces antibodies that show that
L chains are of two types with respect to antigenic specificity; that is,
a single L chain has either a specificity designated kappa ( K ) or one
designated lambda ( A ) . Both L chains in any single molecule of ,G
are always the same, but any one individual’s serum contains a mixture
of molecules showing either the K or
specificity. This reflects the
concept that single cells among those that manufacture anitbodies only
synthesize a single type of L chain.
In contrast to L chains, ,G H chains are found to have a different
set of antigenic specificities existing as four alternate possibilities. These
are termed ,G1, ,G2, ,G3, and ,C4, respectively. As with the L chains,
both H chains of a single antibody inolccule are of the same specificity,
but any single human produces a mixture of varying percentages of all
four kinds of H-chain molecules, each with a K or X L-chain dimer.
Again, this reflects the capacity of synthesis of single Ig-producing cells,
sonic making one kind of ,G, some another. Data are accumulating to
show that both L- and H- antigenic specificitics reflect differences in the
primary amino acid sequences of the chains involved.
B. Allotypes
Still additional antigenic hctcrogcneities are imp0sc.d upon the ,G
molecule. These include a series of genctically controlled polymorphic
JOHN E. CUSHING
Jones proteins and other Ig fragments produced by individuals with
pathological defects ) are leading to a profound understanding of the
subunit structure of these molecules. Both are composed of four chains
of polypeptides, one pair of shorter, “light” ( L ) chains and one pair
of longer, “heavy” ( H ) chains. These chains are relatively similar in
both molecules, the major contrasts between ,G and ,M bcing that
while ,G is a single molecular entity with two combining sites pc’r antibody the ,M molecule consists of ;I complex of five repeating molecular
entities, each grossly similar to a ,G molecule with a total combining
valence of ten. The y M molecule is readily inactivated by mercaptoethanol, where:is the ,
C nioleculc is not, a simple but far from comprehensive example of a contrasting characteristic of the molecules. An
individual serum has all four classes of Ig in variable amounts dcpending upon physiological conditions such as location and length of
immunization.
When the L and H chains of ,G are separated from each other,
they are found to be polypeptides consisting of from 210 to 220 amino
acid residues for the L chains, and around 440 for the H chains. Injection of separate chains into rabbits produces antibodies that show that
L chains are of two types with respect to antigenic specificity; that is,
a single L chain has either a specificity designated kappa ( K ) or one
designated lambda ( A ) . Both L chains in any single molecule of ,G
are always the same, but any one individual’s serum contains a mixture
of molecules showing either the K or
specificity. This reflects the
concept that single cells among those that manufacture anitbodies only
synthesize a single type of L chain.
In contrast to L chains, ,G H chains are found to have a different
set of antigenic specificities existing as four alternate possibilities. These
are termed ,G1, ,G2, ,G3, and ,C4, respectively. As with the L chains,
both H chains of a single antibody inolccule are of the same specificity,
but any single human produces a mixture of varying percentages of all
four kinds of H-chain molecules, each with a K or X L-chain dimer.
Again, this reflects the capacity of synthesis of single Ig-producing cells,
sonic making one kind of ,G, some another. Data are accumulating to
show that both L- and H- antigenic specificitics reflect differences in the
primary amino acid sequences of the chains involved.
B. Allotypes
Still additional antigenic hctcrogcneities are imp0sc.d upon the ,G
molecule. These include a series of genctically controlled polymorphic