High voltage immunoelectron microscopy of complement receptor type 3-mediated capping and internalization of group A streptococcal cell walls by XXXX neutrophils.

@entity1 @entity3954 @entity3584 @entity2348 @entity12009
The mechanism of @entity1 neutrophil clearance of peptidoglycan group A-specific polysaccharide polymers derived from streptococcal cell walls (PG- @entity12009 ) was investigated by high voltage immunoelectron microscopy (HVEM) in order to determine how neutrophils process this highly inflammatory bacterial debris. Neutrophil monolayers were incubated from 5-30 min with serum-opsonized PG- @entity12009 . Cells were lightly fixed with 0.5% @entity3584 , and the PG- @entity12009 was localized on the neutrophil surface by immunogold using antibodies to @entity3954 and 15 nm colloidal gold coupled to goat anti-rabbit IgG. Neutrophils were viewed unsectioned by stereo HVEM. Patches of PG- @entity12009 were distributed randomly on the plasmalemma of well-spread neutrophils within 5 min. In polarized cells, PG- @entity12009 was densely localized on the uropod and retraction fibers. Within 15 min, PG- @entity12009 was predominantly concentrated into a large aggregate, measuring approximately 1 micron in diameter, near the cell margin or nucleus. The aggregate of PG- @entity12009 was engulfed in the vicinity of the indentation of the nucleus (hof). Intact microfilaments were required for aggregation and internalization of PG- @entity12009 . Binding of PG- @entity12009 was dependent upon complement fixation. Furthermore, PG- @entity12009 elicited an increase in density of complement receptor type 3 (CR3, C3bi receptor) on the neutrophil surface as determined by morphometry of immunogold labeled anti-CR3. When cells were stained for both PG- @entity12009 and CR3, co-localization was observed, and stereomicroscopy revealed clusters of CR3 in areas associated with phagocytosis. These data suggest that neutrophils use an efficient mechanism for @entity2348 . Unlike whole streptococci which are phagocytosed at multiple sites, these bacterial cell walls are first collected into a large aggregate, or cap, which is then internalized at one site.
