FIGURE 5.

Blocking 2B4/CD48 homotypic interactions impaired degranulation events without affecting the production of granzyme B and perforin. A, isolated NK cells, cultured with 300 units/ml of IL-2 for 14 days in the presence of isotype control, anti-2B4, anti-CD48, or anti-CD2 mAbs, were incubated with K562 cells at a 1:1 ratio for 6 h. GolgiStop was added for the last 5 h. The cells were then stained with anti-granzyme B or anti-perforin mAbs and assessed by flow cytometry. The data are representatives of a minimum of 3 independent experiments. B, isolated NK cells cultured as above were co-incubated with K562 cells at an E:T ratio of 1:1 for 24 h in anti-granzyme B Ab-coated ELISPOT plates. The spot numbers per well were presented as mean ± S.D. n = 3, *, p < 0.05 and **, p < 0.01, as determined by ANOVA combined with a Tukey post hoc test. C, NK cells cultured as above were co-incubated with K562 cells at an E:T ratio of 1:1 for 6 h. GolgiStop was added for the last 5 h. The cells were stained with anti-CD56 and anti-CD107a Abs and degranulation was assessed by flow cytometry. The values represent the relative CD56⁺CD107a⁺ NK cell number as compared with the isotype control, presented as mean (%) ± S.D., n = 5 (*, p < 0.05, one sample t test).