Journal: Frontiers in Immunology
Article Title: Isatuximab Acts Through Fc-Dependent, Independent, and Direct Pathways to Kill Multiple Myeloma Cells
doi: 10.3389/fimmu.2020.01771
Figure Lengend Snippet: Isatuximab activates NK cells by crosslinking CD38 and CD16. (A) PBMCs were treated with or without 1 μg/ml of Isa* or Isa. After 7 days, NK cell activity was analyzed by intracellular staining for the production of perforin, granzyme-A, granzyme-B, IFN-γ, and TNF-α. (B) 1 × 10 6 cells/ml of purified human NK cells ( n = 3) were cultured overnight with or without the presence of IgG1, Isa, Isa*, F(ab') 2 , and IgG1+F(ab') 2 . Cell culture supernatants were collected and analyzed for the production of IFN-γ and TNF-α by MSD. **** p < 0.001 by unpaired t -test ( n = 3). (C) K562 cells were labeled with calcein AM and co-cultured with purified human NK cells ( n = 7) at the ratio 1:10 in the presence of 1 μg/ml of IgG1 or Isa for 1 h and cytotoxicity measured by calcein AM release. The experiment was performed in technical triplicate, with statistical analysis by two-tailed paired t -test. * p < 0.05. (D) 1 × 10 6 cells/ml of human NK-92 parental, NK-92.CD16 F/F or NK92.CD16 V/V cells ( n = 3) were cultured overnight with or without the presence of 1 μg/ml of IgG1, Isa, Isa*, F(ab') 2 , or IgG1+F(ab') 2 . Culture supernatants were collected and assayed for the production of IFN-γ and TNF-α by MSD. *** p < 0.001 by unpaired t -test ( n = 3). (E) Cytotoxicity against CD38 − JHH6 cells ( n = 3) was measured by calcein AM release. The experiment was conducted in technical triplicate. **** p < 0.0001 by unpaired t -test ( n = 3). (F) NK92.CD16 V/V cells were serum-starved overnight and treated with or without Isa, Isa*, F(ab') 2 , anti-CD16, IL-15 for 15 min prior to cell lysis. Western blotting was used to determine activation of the Src kinase, STAT3 and STAT5. All results are mean (SD). F(ab') 2 , F(ab') 2 portion of isatuximab; GzmA, granzyme-A; GzmB, granzyme-B; IFN-γ, interferon-gamma; IgG1, immunoglobulin G1; Isa, isatuximab; Isa*, isatuximab mutant unable to bind to CD38; MSD, Meso Scale Diagnostics; NK, natural killer; NT, not treated; PBMC, peripheral blood mononuclear cell; TNF-α, tumor necrosis factor-alpha.
Article Snippet: Human CD38 was also detected by commercial anti-CD38 monoclonal antibody (clone HB7; Santa Cruz Biotech and BD Biosciences, San Jose, CA).
Techniques: Activity Assay, Staining, Purification, Cell Culture, Labeling, Two Tailed Test, Lysis, Western Blot, Activation Assay, Mutagenesis