Where are the receptors for Streptococcus pyogenes located on the tonsillar surface epithelium?

Streptococcus pyogenes is the most frequent causative agent of acute pharyngotonsillitis (AT). The first events in the etiopathogenesis of an AT infection caused by these bacterial pathogens are their penetration through the mucus film covering the oropharyngeal mucosa, and their attachment to the surface epithelium. Adherence of S. pyogenes to tonsillar epithelial cells is a precondition for bacterial colonisation, for triggering off cell activation, internalising of bacteria into the epithelial cells and cytokine release from the epithelial cells with subsequent induction of an inflammatory reaction in underlying tissues. Scanning and transmission electron microscopic studies revealed that the surface epithelium of the human palatine tonsils consisted of a weakly keratinized, stratified squamous epithelium built up of pentangular cells where the apical cell surface formed an irregular pattern of microridges. The distance between two adjacent microridges was roughly one-third of the diameter of a S. pyogenes bacterium. By using gold-labelled antiserum to S. pyogenes, we showed that the target region for these pathogens on the epithelial cells during an on-going AT infection was located on the crests of the microridges where bacterial pili made adhesin-receptor contact with the tonsillar surface epithelium.