Fig. 2: The fully human anti-CD229 antibody 2D3 binds to MM cells and B and T cells.

a Binding of the fully human IgG₁ antibody 2D3 to 293 cells individually expressing 5300 full-length, human membrane proteins as determined by flow cytometry. Fc gamma receptor 1A (FCGR1A) serves as a positive control. b K562 cells were stably transduced with a human CD229 expression construct and stained with 2D3. Binding was determined by flow cytometry. c Left: The extracellular domain of CD229 consists of two variable and two constant Ig-like domains. In a human CD229 expression construct, each of these domains was replaced with the corresponding mouse homolog as 2D3 did not show any reactivity to mouse CD229 (Supplementary Fig. 2A). Right: Binding by 2D3 and the commercially available CD229-specific antibody HLy9.1.25³³ to the four chimeric proteins expressed on 293T cells was determined by flow cytometry. d MM cells were isolated from primary bone marrow samples from three patients with MM using a commercially available MM cell purification kit (Stemcell Technologies). Purified MM cells were stained with 2D3 and binding was determined by flow cytometry. e Bone marrow samples from seven patients with newly diagnosed (ND) and eight patients with relapsed/refractory (RR) MM were stained with 2D3 and analyzed by flow cytometry. Data represent mean ± standard deviation and statistical significance was determined by two-sided Student’s t-test. f CD34⁺ hematopoietic progenitors, neutrophils, monocytes, g natural killer (NK) cells, B cells, and T cells were isolated from peripheral blood from a healthy donor using commercially available purification kits (Stemcell Technologies). Cells were stained with 2D3 and analyzed by flow cytometry. Source data are provided as a Source Data file.