Figure 2.

F(ab′)₂ of anti-CD16 mAb 3G8 blocks lysis of some target cells. NK clone 721 (CD56⁺, CD16⁺, NKIR2⁺ NKIR1⁻, NKB1⁻, CD94⁺) was incubated with 40 μg/ml of the F(ab′)₂ fragment of either the anti-CD16 mAb 3G8 or the anti-CD99 mAb 12E7 for 1 hr on ice. The NK clone 721 incubated with no mAb was used as a control. Cells were washed and incubated with the ³⁵S-labeled target cells at an E:T ratio of 5:1 in a 5-hr killing assay. The figure shows one representative experiment of three performed. Similar results were obtained with various E:T ratios and with 10 other NK clones and 10 other NK lines from different donors.