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Figure S4. KIR3DS1⁺ NK cells express additional inhibitory KIRs. (A) The flow plot demonstrates the expression of additional KIRs on the surface of KIR3DL1⁺ (z27^hi), KIR3DS1⁺ (z27^low), or double-negative NK cells (z27^neg) using combined antibodies directed at CD158a (KIR2DL1/KIR2DS1) and CD158b (KIR2DL2/KIR2DL3/KIR2DS2). (B) To further confirm the specific presence of inhibitory KIRs in NK cell subpopulations, NK cells were sorted based on DX9 and z27 staining to generate pure populations of KIR3DL1⁺, KIR3DS1⁺KIR3DL1⁻, and double-negative NK cells from an individual that encoded KIR2DL1, 2DL3, 2DL4, 2DL5, 2DS1, 2DS3, 2DS4, 3DL1, and 3DS1. RNA was extracted from each sorted population and reverse transcribed to complementary DNA, after which quantitative PCR was performed to assess the level of inhibitory KIR expression. KIR3DS1⁺ NK cells expressed KIR2DL1, 2DL3, 2DL5, and NKG2A.