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Monoclonal antibodies block cell-cell adhesion in Dictyostelium discoideum.

1983; Elsevier BV; Volume: 258; Issue: 8 Linguagem: Inglês

10.1016/s0021-9258(18)32477-3

1083-351X

R. W. Springer, S H Barondes,

Monoclonal and Polyclonal Antibodies Research

Of 39 monoclonal antibodies that bind the cell surface of aggregating Dictyostelium discoideum, 4 block 76-98% of cell-cell adhesion measured in an in vitro assay.The active antibodies all bind in the range of lo6 antigenic sites/cell surface and react with more than one material on nitrocellulose blots prepared after polyacrylamide gel electrophoresis of whole aggregating cells in sodium dodecyl sulfate.Active antibodies can be grouped into two classes, each with two very similar members.Class I binds several molecules that are prominent in aggregating cells but scarce or undetectable in vegetative cells, blocks cell adhesion only in the presence of EDTA, and has no detectable effect on cell morphology.Class 11 binds a wide range of molecules present in both vegetative and aggregating cells, inhibits adhesion as well in the absence as in the presence of EDTA, and reversibly alters cell shape.Cellular association is believed to be mediated by specific molecules on and between cells.Attempts to identify them often begin by raising antisera against crude cellular antigens in the hope of obtaining one that blocks cell-cell adhesion (1).Such antisera are the basis of an assay for cell adhesion molecules, operationally defiied as those that neutralize its anti-adhesion activity.Much of the work with this approach has been done with the cellular slime mold Dictyostelium discoideum, as reviewed recently (2).One major finding is that few antibodies directed against cell surface antigens block cell adhesion, so that those that do may well react with molecules that play a direct role in the adhesion process.The substances identified as neutralizers of adhesion blocking antisera include glycoproteins with M, 80,000 (1, 3), 95,000 (4, 5), and 150,000 (6), and a pronaseresistant glycoconjugate fraction of high molecular weight (7).An important limitation of this approach is that the complex antisera initially used for screening cannot be used as affinity absorbants to purify the presumed cell adhesion molecules, since they also react with so many irrelevant cellular components.In practice then, purification is done by conventional