Coated uPA reduces the cytotoxic potential of Ly49E-positive fetal NK cells independent from uPAR expression. (A) Anti-Ly49E mAb (CM4) staining of IL-2–cultured FD17 cells (solid line) discriminated Ly49E^neg, Ly49E^dim, and Ly49E^bright cells (M1, M2, and M3, respectively) after NK1.1⁺CD3⁻ gating. Isotype control staining is shown as a dotted line. (B) The percentage uPA-mediated reduction of CD107 expression in the 3 gated NK populations. C57BL/6 or uPAR KO FD17 cells were incubated in anti-NK1.1 (10 μg/mL) plus uPA or BSA (200 ng/well) coated wells. No (filled symbols; C57BL/6: n = 7; uPAR KO: n = 5) or anti-Ly49E (4D12) F(ab′)₂ fragments (open symbols; n = 4) were added. The mean is represented by a horizontal bar. *P < .05; **P < .01 (Student t test).