Two chick embryonic adhesion systems: molecular vs tissue specificity

We have investigated the adhesive properties of cells from several neural and nonneural chick embryonic tissues dissociated using modifications of the standard dissociation procedures employed routinely in this laboratory to obtain retinal cells. Each of these tissues (7-day optic tectum, retina, and heart, and 3.75-day limb bud) displayed both Ca++-dependent (CD) and Ca++-independent (CI) aggregation, the relative rates of which differed from tissue to tissue. In every case, cells prepared so as to display one mode of aggregation or the other cross-adhered readily to cells--regardless of tissue origin--displaying the same mode of aggregation. Cross adhesion was negligible between cells--even from the same tissue--prepared so as to display different modes of aggregation. Anti-retinal Fab molecules which inhibit selectively either the CI or CD aggregation of retina cells strongly inhibited the corresponding aggregation of optic tectum cells, but had no effect upon the aggregation (CI or CD) of heart cells. These results demonstrate the existence in the tissues examined of dual adhesion mechanisms similar in Ca++ dependence and recognition properties to those of the retina, but showing certain immunological distinctions from the latter. The immunological relationship among the adhesion mechanisms from the various tissues is under continuing investigation.