Erythrocytes as Target Cells for Testing Bacterial Adhesins

This chapter describes experimental approaches to determine the specificities of the Escherichia coli adhesins using red blood cells (RBCs) as target cells. Similar methods have been used for studying hemagglutinins of other bacteria. When RBCs are used as target cells for studying bacterial adhesins, the important limitations of the model must be realized: (1) some bacterial adhesins known to be involved in the pathogenic process do not cause hemagglutination (HA) and (2) HA activity is not always relevant to the specific tissue target of the tested adhesin. In studies aimed at characterizing the role of adhesins in the development of natural infections, it is always recommended to compare the binding of the tested bacteria to RBCs with that to the cells relevant to the adhesion function. The possible experimental approach of such a comparison is to demonstrate that both HA and interaction of the tested bacteria (or of the isolated adhesin) with other cells can be inhibited by the hemagglutinin-specific antibodies or/and by the similar putative receptor components. The isolated hemagglutinin inhibits the binding of whole bacteria to the target cells. Another approach is to separate the bacterial population rich in hemagglutinin and to show the correlation between the HA titer and the rate of adhesion to other target cells.