Sodium azide

Antibodies (listed in Table S1 in Supplementary Material) were either pre-conjugated from the manufacturer (Fluidigm, San Francisco, CA, USA) or conjugated in-house with the appropriate metal isotopes. Between 200 and 400 µg pure mAbs (carrier-protein-free) from various manufacturers were coupled to Lanthanide from the MaxPar Antibody Labeling Kit X8 4Rxn (Fluidigm). Conjugated Abs were adjusted to 1 µg/µl in Ab Stabilizer Solution (Candor, Biosciences, Wangen, Germany), supplemented with 0.01% sodium azide (Santa Cruz Biotechnology), and stored at 4°C. Abs conjugated in-house, as well as those obtained pre-conjugated, were titrated and validated on samples that were processed identically to those used in the study.

Antibody-element conjugation was performed as previously described (49 (link)). Pure (carrier-protein–free) monoclonal or polyclonal antibodies from various manufacturers were coupled to elements using MAXPAR lanthanide labeling kits (Fluidigm, San Francisco, CA), as indicated in the manufacturer’s preload method for 400 mg of antibody. The antibody-element combinations are shown in Fig. S11A for analysis of human samples and Fig. S11B for cynomolgus macaque samples. Antibody-element conjugates were adjusted to 1 mg/mL in antibody stabilizer buffer (Candor Bioscience, Wangen, Germany), supplemented with sodium azide (Santa Cruz Biotechnology) to a final concentration of 0.01%, and stored at +4°C in sterile conditions throughout the study. Antibody-element combinations were titrated and tested in CyTOF using cells from healthy humans to obtain optimal staining concentrations.