Protein distorsion-derived mechanism of signal discrimination in monocytes revealed using Congo red to stain activated cells.
The supramolecular dye Congo red was used to check whether monocyte activation may be mediated by a torsion-dependent mechanism preventing transduction of weak random signals in cell contacts in a way corresponding to the discrimination mechanism found in complement fixation by immune complexes. Tight cell-cell contacts generating torsional effects may be expected to produce alteration of receptor structure, making them accessible for binding of supramolecular dyes. In this study, Congo red was used to observe the binding accessibility of (1) monocytes (human) induced by contact with cancer cells (HCV29T, human), (2) monocytes (mouse) stimulated by interaction with heat-aggregated IgG and (3) monocytes (mouse) activated by rosetting in the presence of an SRBC-anti-SRBC system. Microscopic studies confirmed the activation of monocytes manifested by their clustering and Congo red binding, but only tightly clustered cells appeared to attach the dye on the surface. Usually not the whole cell surface is found to be engaged in dye complexation. Staining occurs predominantly on the interfaces of reacting cells, making probable the suggestion that cell adhesion receptors are involved in dye binding. The cells in the central areas of tight clusters undergo accelerated death. In the presence of Congo red they are easily recognized as intensely fluorescent. The characteristic localization of dead cells in the central area of clusters indicates that death is not random but results from cell activation. The role of Congo red in this process remains to be clarified. The staining characteristics of monocytes after application of Congo red probably discloses the initial step in signal transduction generated by torsional movements in receptor proteins.
D000818:Animals; D045744:Cell Line, Tumor; D004396:Coloring Agents / Q000378:metabolism*; D003224:Congo Red / Q000378:metabolism*; D006801:Humans; D007147:Immunoglobulin Light Chains / Q000737:chemistry / Q000378:metabolism; D051379:Mice; D008958:Models, Molecular; D009000:Monocytes / Q000166:cytology / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D015398:Signal Transduction / Q000502:physiology*
D004396:Coloring Agents; D007147:Immunoglobulin Light Chains; D003224:Congo Red