Anti-TCII antibodies inhibit in vitro cell growth to varying degrees. Cells were seeded at 5,000 cells/well (in 0.1-mL volumes) and cultured in RPMI lacking Cbl and folic acid (medium I), supplemented with 10% QUSO-treated FCS and 100 ng/mL recombinant human holo-TCII. Serial dilutions of anti-TCII monoclonal antibodies (mAbs) were added to the wells and viability of BW5147 cells (A) and K562 cells (B) assessed after 7 days in culture using the MTT reduction assay. Results are expressed as the mean ± SEM of triplicate determinations. mAb 3-9 (○), mAb 2-6 (•), mAb 4-7 (▪), mAb 3-11 (▴), mAb 1-9 (□), mAb 5-18 (▵), mAb 2-2 (▾), and mAb 3-5 (▿). Control cultures were grown in presence of TCII (100 ng/mL) and absence of antibody (○). Background represents cell viability in the absence of holo-TCII (□).