ULBP2-BB4 reveals antitumor activity in a xenograft MM model. Effect of PBL + ULBP2-BB4 (•), PBLs (▵) and no treatment (○) on the tumor growth of subcutaneous RPMI-8226 tumors in nude mice is shown. The mean tumor volume ± SD (n=5) is shown. Statistical analysis of the tumor volumes measured was done with the paired t test using GraphPadPrism software. The differences between PBLs and the control are not significant (P = .14; n = 5).