14. C E L L A G G R E G A T E S
511
prises several functionally complementary cell types. There is considerable evidence that in the first stages of aggregation the cells are
clustered at random and that subsequently they become reshuffled and
sorted out in accordance with their original characteristics, affiliations,
and regional preferences (Moscona and Moscona, 1952; Weiss and
James, 1955; Trinkaus and Groves, 1955; Moscona, 1956, 1957a;
Auerbach and Grobstein, 1958). Reconstruction of tissues in aggregates
appears thus to involve mobility of the reattached cells and of the
emerging cell groups, and to depend on cellular properties usually
referred to as affinities, complementary matching (Weiss, 1958) and
self-recognition (Burnet, 1961). Since the evidence for sorting out of
aggregated cells comes largely from work with heterotypic cell combinations, this issue is referred to in the next section.
Considerable work has been done on interspecific combinations of
isotypic cells, derived from early chick and mouse embryos and commingled in suspension. The purpose of these interspecific cell combinations was to define more closely the framework of properties
involved in reassociation of embryonic cells in this system, i.e. whether
they were narrowly species-specific. Cells from these two species can be
distinguished by their morphology and staining properties. In coaggregates formed by isotypic cells from mouse- and chick-embryos in
properly matched developmental stages, the cells remained interspersed, established structurally effective contacts, and co-operated in
the construction of chimaeric fabrics. Interspecific chimaeras were
obtained in combinations of liver, cartilage, retina and kidney cells
(Figs. 10-13) (Moscona, 1957a, 1961a, c, 1962b), cardiac myoblasts
(Wilde, 1959) and thymus (Auerbach, 1961), by self-aggregation and
by mediated aggregation. Therefore, according to these results, factors
involved in histotypic matching and arrangement of aggregating cells
reflect, primarily and in the systems studied, similarities in cell function
and tissue derivation rather than differences in taxonomic origin. That
such chimaerism is not due to the treatment during dissociation is
shown by results of heterotypic combinations (p. 516). It should be
restated that histochimaeric association of cells in interspecific compounds depends on the cells being in closely matched developmental
and functional states; cells in different stages of differentiation, although
from homologous tissues, tend to group separately; there is thus a
definite correlation between the "affinities" and "recognition effects"
of cells and their metabolic features.
In interspecific aggregates, size differences of cells result, with time,
in structural disproportions; this and cell divisions tend, progressively,
to blur out the initial chimaeric organization and to impose a secondary
pattern on the aggregated system. Actual grouping behavior ofthe cells
511
prises several functionally complementary cell types. There is considerable evidence that in the first stages of aggregation the cells are
clustered at random and that subsequently they become reshuffled and
sorted out in accordance with their original characteristics, affiliations,
and regional preferences (Moscona and Moscona, 1952; Weiss and
James, 1955; Trinkaus and Groves, 1955; Moscona, 1956, 1957a;
Auerbach and Grobstein, 1958). Reconstruction of tissues in aggregates
appears thus to involve mobility of the reattached cells and of the
emerging cell groups, and to depend on cellular properties usually
referred to as affinities, complementary matching (Weiss, 1958) and
self-recognition (Burnet, 1961). Since the evidence for sorting out of
aggregated cells comes largely from work with heterotypic cell combinations, this issue is referred to in the next section.
Considerable work has been done on interspecific combinations of
isotypic cells, derived from early chick and mouse embryos and commingled in suspension. The purpose of these interspecific cell combinations was to define more closely the framework of properties
involved in reassociation of embryonic cells in this system, i.e. whether
they were narrowly species-specific. Cells from these two species can be
distinguished by their morphology and staining properties. In coaggregates formed by isotypic cells from mouse- and chick-embryos in
properly matched developmental stages, the cells remained interspersed, established structurally effective contacts, and co-operated in
the construction of chimaeric fabrics. Interspecific chimaeras were
obtained in combinations of liver, cartilage, retina and kidney cells
(Figs. 10-13) (Moscona, 1957a, 1961a, c, 1962b), cardiac myoblasts
(Wilde, 1959) and thymus (Auerbach, 1961), by self-aggregation and
by mediated aggregation. Therefore, according to these results, factors
involved in histotypic matching and arrangement of aggregating cells
reflect, primarily and in the systems studied, similarities in cell function
and tissue derivation rather than differences in taxonomic origin. That
such chimaerism is not due to the treatment during dissociation is
shown by results of heterotypic combinations (p. 516). It should be
restated that histochimaeric association of cells in interspecific compounds depends on the cells being in closely matched developmental
and functional states; cells in different stages of differentiation, although
from homologous tissues, tend to group separately; there is thus a
definite correlation between the "affinities" and "recognition effects"
of cells and their metabolic features.
In interspecific aggregates, size differences of cells result, with time,
in structural disproportions; this and cell divisions tend, progressively,
to blur out the initial chimaeric organization and to impose a secondary
pattern on the aggregated system. Actual grouping behavior ofthe cells