Opsonized streptococcal cell walls cross-link human leukocytes and erythrocytes by complement receptors

Infect Immun. 1985 Sep;49(3):550-6. doi: 10.1128/iai.49.3.550-556.1985.


Serum-opsonized group A streptococcal cell walls, consisting of peptidoglycan-polysaccharide polymers (PG-APS), induced monolayers of human neutrophils, monocytes, and eosinophils to aggregate. When erythrocytes were present in the incubation medium, they also were associated with the leukocyte aggregates. By immunofluorescence staining, PG-APS was localized at the site of cell-to-cell contact. By scanning electron microscopy the cells appeared to adhere to one another by surface contact; filopodia often acted as connectors, particularly in leukocyte-erythrocyte interaction. Cellular binding of PG-APS and aggregation were dependent upon C3 fixation. No aggregation was observed when heat-inactivated serum was used as an opsonin. In contrast to peptidoglycan, an activator of the alternative complement pathway, the group-specific polysaccharide moiety of PG-APS induced no cellular aggregation. Rosette formation was observed in suspensions when neutrophils were incubated with erythrocytes coated with C3b-opsonized PG-APS. Cell monolayers bound serum-opsonized PG-APS, but aggregation was observed only when serum was present in the incubation medium. Similar results were obtained with C5-deficient serum. No aggregation was observed with heat-inactivated serum or bovine serum albumin. A heat-labile serum component(s) appears to be required to elicit leukocyte aggregation. It is suggested that C3 fixed to PG-APS acts as a bridge to link cells together in clusters as a result of common recognition of C3 by leukocyte and erythrocyte complement receptors.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Cell Aggregation
  • Cell Communication
  • Cell Wall / immunology
  • Complement C3 / immunology
  • Erythrocyte Aggregation*
  • Fluorescent Antibody Technique
  • Humans
  • Leukocytes / immunology*
  • Microscopy, Electron, Scanning
  • Peptidoglycan / analysis
  • Phagocytosis*
  • Polysaccharides, Bacterial / analysis
  • Rabbits
  • Receptors, Complement / immunology*
  • Rosette Formation
  • Streptococcus


  • Complement C3
  • Peptidoglycan
  • Polysaccharides, Bacterial
  • Receptors, Complement