The nature of receptors in mammalian cells for B. pertussis and in particular filamentous hemagglutinin (FHA) is currently being investigated. Results indicate that virulent strains of B. pertussis can bind to certain glycolipids present in lung tissues. The structure of these glycolipids is being investigated as is the nature of the bacterial adhesions mediating this interaction. Our studies suggest that FHA may contain a lectin site that interacts with sulfated glycolipids, cell surface receptors which are present in large quantities in human trachea and lungs. We are currently mapping this lectin binding site on the FHA molecular. Recent evidence also suggests that large molecular weight sulfated glycoproteins can also bind to FHA. The role of proteoglycan as receptors for B. pertussis is being pursued.