476
JOHN E. CUSHING
process of various stages of evolutionary expression among the fishes.
They also noted the great potential interest inherent in subunit analysis
of the Ig involved, and the need for clarifying the “limits of resolving
power” of lower vertebrate antibody with respect to the recognition of
antigenic specificities (see Section 11, F ) ,
Progressive studies since 1964 have demonstrated that modem elasmobranchs and several other species of fish produce both 19 S-like and
7S-like Ig and may possess some capacity for immunological memory,
although this point is still equivocal, being difficult to demonstrate (Sigel
and Clem, 1966; Clem and Small, 1967; Marchalonis and Edelman, 1965,
1966). Elasmobranch antibodies are similar to those of mammals in
being composed of light and heavy chain subunits. They differ, however,
in that the H chains of both kinds of antibodies appear to be identical
with respect to such characteristics as amino acid composition, size,
carbohydrate content, and antigenicity. Acrylamide-gel disc electrophoresis shows that elasmobranch light chains probably exists as two
classes and are heterogeneous to the same degree as those of humans.
Chain sequence studies by Suran et al. (1967) show that the N-terminal
pentapeptide amino acids sequence of most L and H chains of leopard
shark was identical to human K chains. This chain type was predominant
(80-100%) in both L and H leopard shark chains, The remaining chains
are presumed to have blocked N-terminal amino acid groups similar
to the A and H chains of human chains, The unblocked H chains were
very different in sequence from the blocked rabbit and human H chains.
Pollara et al. (1968) report a study on the H and L chains of paddlefish, Polyodon spathula, 19 S Ig (this species apparently does not make
a 7 S antibody). The intact molecule had a molecular weight of 870,000
k 7,300, its H chain that of 75,000 t 750, and its L chain 23,500 & 560.
These values correspond to those of human and rabbit yM H chains,
shark H chains, and the L-chain molecular weights of other species of
fish and mammals. N-terminal pentapeptides ( ASP-Ile-Val-Ile( Leu) -
Thr-) are not only identical for H and L chains but also homologous
to those for sharks and mouse and human K L chains. The demonstration
of an unblocked N-terminal amino acid in H chains from this lower
vertebrate is the second such, the other being reported in the leopard
shark (Suran et al., 1967). This is in contrast to mammals where cyclized
N (glutamine pyrollidone carboxylic acid) appears as the N terminus
of many 7s H chains. A low yield of N-terminal aspartic acid from L
chains suggests that as in elasmobranchs there may be two classes of
L chains, a K plus a A type with blocked sequence.
The homologies just reviewed strengthen the concept of a common
origin of the genetic apparatus for antibody synthesis from a primitive
JOHN E. CUSHING
process of various stages of evolutionary expression among the fishes.
They also noted the great potential interest inherent in subunit analysis
of the Ig involved, and the need for clarifying the “limits of resolving
power” of lower vertebrate antibody with respect to the recognition of
antigenic specificities (see Section 11, F ) ,
Progressive studies since 1964 have demonstrated that modem elasmobranchs and several other species of fish produce both 19 S-like and
7S-like Ig and may possess some capacity for immunological memory,
although this point is still equivocal, being difficult to demonstrate (Sigel
and Clem, 1966; Clem and Small, 1967; Marchalonis and Edelman, 1965,
1966). Elasmobranch antibodies are similar to those of mammals in
being composed of light and heavy chain subunits. They differ, however,
in that the H chains of both kinds of antibodies appear to be identical
with respect to such characteristics as amino acid composition, size,
carbohydrate content, and antigenicity. Acrylamide-gel disc electrophoresis shows that elasmobranch light chains probably exists as two
classes and are heterogeneous to the same degree as those of humans.
Chain sequence studies by Suran et al. (1967) show that the N-terminal
pentapeptide amino acids sequence of most L and H chains of leopard
shark was identical to human K chains. This chain type was predominant
(80-100%) in both L and H leopard shark chains, The remaining chains
are presumed to have blocked N-terminal amino acid groups similar
to the A and H chains of human chains, The unblocked H chains were
very different in sequence from the blocked rabbit and human H chains.
Pollara et al. (1968) report a study on the H and L chains of paddlefish, Polyodon spathula, 19 S Ig (this species apparently does not make
a 7 S antibody). The intact molecule had a molecular weight of 870,000
k 7,300, its H chain that of 75,000 t 750, and its L chain 23,500 & 560.
These values correspond to those of human and rabbit yM H chains,
shark H chains, and the L-chain molecular weights of other species of
fish and mammals. N-terminal pentapeptides ( ASP-Ile-Val-Ile( Leu) -
Thr-) are not only identical for H and L chains but also homologous
to those for sharks and mouse and human K L chains. The demonstration
of an unblocked N-terminal amino acid in H chains from this lower
vertebrate is the second such, the other being reported in the leopard
shark (Suran et al., 1967). This is in contrast to mammals where cyclized
N (glutamine pyrollidone carboxylic acid) appears as the N terminus
of many 7s H chains. A low yield of N-terminal aspartic acid from L
chains suggests that as in elasmobranchs there may be two classes of
L chains, a K plus a A type with blocked sequence.
The homologies just reviewed strengthen the concept of a common
origin of the genetic apparatus for antibody synthesis from a primitive