Fig. 5: Blockade of the MHC-I–KIR interaction enhances NK cell-mediated anti-T–cell lymphoma activity in mice in vitro and in vivo.
a The murine T-lymphoma cell line, EL4-hCD20, highly expresses H-2Kb versus the normal T cells of wild-type C57BL/6 mice. H-2Kb is the MHC class I molecule for C57BL/6 mice. b Two independent sets of experiments, one based on flow cytometry and one based on LDH release detection, indicated increased ADCC against murine T-lymphoma cells during Ly49 C/I blockade. Ly49 C and Ly49 I are specific inhibitory receptors on NK cells in mice (N = 6). Data were presented as mean values +/– SEM. The p values were calculated using paired, two-tailed student’s t test. c Schematic representation of the in vivo mouse experiment. C57BL/6 mice were inoculated subcutaneously with 1 × 105 EL4-hCD20 T-lymphoma cells. After tumor inoculation, mice received 250 µg of therapeutic anti-hCD20-mIgG2a or isotype IgG2a control on day 3 and once weekly for three weeks, 200 µg of blocking anti-Ly49 C/I F(ab’)2 or isotype IgG2a F(ab’)2 on day 3 and biweekly for three weeks, or a combination of anti-hCD20-mIgG2a and anti‑Ly49 C/I F(ab’)2. Therapeutic and blocking antibodies were administered i.p. The schematic representation is created with BioRender.com. d Tumor tracking and intensity of luminescence signals from tumor cells as measured by IVIS (N = 10). On day 3 before treatment, the mice were confirmed to have successful EL4-hCD20 tumor inoculation, and the intensity of luminescence signals was approximately equal in each group. On day 9 after treatment, tumor cells remained only in the skin and no metastasis had occurred. In addition, the intensity of luminescence signals indicated that Ly49 blockade enhances the anti-T–cell lymphoma activity of anti-hCD20 therapeutic antibody. Data were presented as mean values +/– SEM. e The tumor growth curve illustrated that both anti-hCD20 therapeutic antibody and Ly49 C/I F(ab’)2 blocking antibody were able to inhibit tumor growth in the skin, and the combination of both antibodies significantly inhibited tumor growth in the skin (N = 10). Data were presented as mean values +/– SEM. The p values were calculated using unpaired, two-tailed student’s t test from the data on day 13. n.s., not significant. f The combination of anti-hCD20 therapeutic antibody and Ly49 C/I F(ab’)2 blocking antibody against T-cell lymphoma in the skin significantly increased overall survival (N = 10). The p values were calculated using simple survival analysis (Kaplan-Meier). n.s., not significant. Source data are provided as a Source Data file.
