Localization of PMN-binding phage clones by immunofluorescence. PMN isolated from peripheral blood were incubated with phage clones, fixed with paraformaldehyde, permeabilized with Triton X-100, and labeled with biotinylated polyclonal antibodies as described in Materials and Methods. There was a bright membrane staining after incubation with the FGPNLTGRW (A) or DLVTSKLQI (C) displaying phage. Incubation of PMN with an irrelevant phage resulted in no detectable immunofluorescence (E). Cytoplasmic staining suggestive of phage internalization was not detected. For orientation, the corresponding Nomarski images are shown in (B), (D), and (F). As can be seen, phage incubation labeled only part of the neutrophils. Incubation with the CKDGLFLGSWLC-displaying phage yielded staining patterns comparable with those found with the other PMN-binding phage (data not shown).