Chapter 11 Univalent Antibody Fragments as Tools for the Analysis of Cell Interactions in Dictyostelium

Abstract

Publisher Summary Labeled antibodies are routinely used in developmental biology for the localization of antigens and for their quantitative determination. Antibodies can, however, also be applied as probes that inhibit or stimulate developmental processes by interaction with specific cell surface constituents. This chapter focuses on this aspect. Intact immunoglobulins, when applied to living cells, have the disadvantage of agglutinating cells and inducing antigen redistribution in the form of patches and caps. This can be avoided by the use of univalent antibody fragments. In 1959, papain digestion was used that is the standard technique for the preparation of antigen binding fragments (Fab). Because the cells in Dictyosteliurn discoideurn (Dd) are single at the beginning of development and aggregate thereafter, this microorganism is unusually suitable for the analysis of cell interactions by Fab. Studies on cell adhesion in the neuroretina of the chicken among sea urchin blastomeres and in mammalian embryos have demonstrated that techniques similar to those described in the chapter for Dd can be applied to a variety of embryonic systems. The main conclusion from the use of Fab as an adhesion blocking agent is that processes essential for cell-to-cell adhesion are linked to specific loci on the cell surface. The antigenic material present at these loci covers only a small fraction of the surface area rather than forming a continuous surface coat. Fab molecules can bind to other surface sites in comparatively large numbers without blocking adhesion.