Streptococcal adherence to Langerhans cells: a possible step in the pathogenesis of streptococcal pharyngitis

Group A streptococci are nonmotile and have no structures that would enable them to penetrate submucosally into the pharynx. We have postulated that they adhere to host pharyngeal mucosal cells called Langerhans cells that are motile and could transport them into deeper tissues. We used a microscopic assay to assess the adherence of streptococci to cells from normal pharyngeal scrapings after the cells and bacteria were incubated in vitro. Langerhans cells were identified by immunofluorescent staining for the CD1a antigen. Nonstaining cells were considered to be keratinocytes. Of the 2279 cells examined from 9 subjects, 92.6% were keratinocytes and 7.4% were Langerhans cells. Only 1.8% of the 2111 keratinocytes had > 50 bacteria attached in this assay, while 76.2% of the 168 Langerhans cells had > 50 attached bacteria. Thus, under the conditions of this study, group A streptococci adhere preferentially to Langerhans cells from the pharynx. Adherence to these motile cells may provide a mechanism through which pathogenic streptococci may be transported into submucosal tissues.