Impaired immunologic synapse formation between Mac-1^−/− PMNs and BsAb-coated tumor cells.

(A) SK-BR-3 cells were biotinylated and incubated with Tg mouse PMNs (Mac-1^+/− and Mac-1^−/−) in the presence of BsAb [A77 × 520C9]. On fixation after 30 minutes, cells were stained with streptavidin-FITC. Immunologic synapses were analyzed by confocal microscopy and were quantified by scanning cells through thex/y direction for the presence or absence of membrane-FITC staining at interaction sites. At least 50 PMNs adhered to SK-BR-3 cells were analyzed randomly per sample. Results are expressed as the percentage of open immunologic synapses (mean ± SEM [n = 4]), (*P < .005). (B) Electron micrographs of Tg Mac-1^+/− PMNs (upper) and Tg Mac-1^−/− PMNs (lower) adhered to BsAb-coated tumor cells. Original magnifications × 9000.