Circulating platelet-leukocyte complexes and surface-bound C3 in a patient with EHEC-associated HUS. A pediatric HUS patient had increased levels of circulating platelet-monocyte (A) and platelet-neutrophil (B) complexes during the acute phase of disease compared with levels obtained after recovery and with pediatric controls (n = 5). Levels of platelet-monocyte (A) and platelet-neutrophil (B) complexes with surface-bound C3 were elevated during the acute phase of disease and decreased at recovery to levels similar to those seen in the pediatric controls.