Positive cooperativity in the adherence between elementary bodies of Chlamydia trachomatis strain UW-31 and HeLa cells

Abstract The adherence of purified elementary bodies of Chlamydia trachomatis strain UW-31 to monolayer cultures of HeLa 229 cells exhibited kinetic evidence of positive cooperativity. An abrupt increase in the rate of adherence occurred as chlamydial dose was increased. Only freshly isolated chlamydiae showed this behavior. In the presence of the lectin wheat germ agglutinin, the stimulated adherence showed typical Michaelis-Menten kinetics. The results suggest that chlamydiae may promote their own binding to the host-cell surface, and the lectin, when cell-bound, may provide additional chlamydiae-binding sites.