Anti cd19

GFP- and tdTomato-tagged F-Tractin were gifts from Michael Schell (Uniformed Services University, Maryland). Alexa Fluor-conjugated phalloidins were purchased from Thermo Fisher. Anti-mDia1 antibody was purchased from Thermo Fisher (PA5-27607). HRP-conjugated mouse anti-β-actin antibody was purchased from Santa Cruz (SC-47778 HRP). Rabbit anti-CD79a (#3351), anti-PCD79a (#5173), anti-CD19 (#3574), and anti-PCD19 (#3571) were purchased from Cell Signaling Technologies. Anti-M2A was purchased from MilliporeSigma (#M8064). CK-666 and SMIFH2 were purchased from MilliporeSigma and used at final concentrations of 100 μM and 25 μM, respectively. pnBB and paBB were purchased from Cayman Chemicals and used at a final concentration of 25 μM. DMSO vehicle control was purchased from MilliporeSigma. CellMask Deep Red Plasma Membrane Stain was purchased from Thermo Fisher. Alexa Fluor 488- (#111-545-003), 594- (#111-585-003), and 647- (#111-605-003) conjugated goat, anti-rabbit secondary antibodies were purchased from Jackson ImmunoResearch. Goat anti-mouse IgG Fcγ fragment-specific antibody (#115-005-008) and goat anti-mouse IgM, µ-chain-specific antibodies (#115-005-020) were purchased from Jackson ImmunoResearch. Anti-rabbit-HRP (#32260) was purchased from Thermo Fisher.

PBMCs from COVID-19 recovered patients and healthy donors were incubated with 10 μg/ml biotin-F(ab′)₂ anti-human Ig(M + G) on ice for 30 min, plus 20 μg/ml streptavidin on ice for 10 min, and then activated at 37 °C for indicated times. Cell lysates were used for electrophoresis in SDS–polyacrylamide gel, electrotransferred onto a nitrocellulose membrane, and then probed with the following specific antibodies: anti-pCD19 (Cat# 3571S, Cell Signaling Technology, USA), anti-CD19 (Cat# 90176, Cell Signaling Technology, USA), anti-pBtk (Cat# ab52192, Abcam, USA), anti-Btk (Cat# 8547S, Cell Signaling Technology, USA), anti-pPI3K (Cat# 4228S, Cell Signaling Technology, USA), anti-pAkt (Cat# 4060L, Cell Signaling Technology, USA), anti-pFoxO1 (Cat# 9461S, Cell Signaling Technology, USA), anti-pmTOR (Cat# 5536S, Cell Signaling Technology, USA), and anti-pS6 (Cat# 4856S, Cell Signaling Technology, USA). After incubated relative secondary antibodies, immunoreactive bands were presented and captured with the ChemiDoc XRS + imaging systems (Bio-Rad). β-actin or GAPDH was used as the loading control.

The following antibodies were used for protein detection: anti-CD19–PE (Beckman Coulter; IM1285U), anti-CD19 (Cell Signaling; 3574), anti-CD19 3G7 (Origen; TA506234), anti-CD19 HD37 (Thermo Fisher; MA1-34005), anti-VSVg–fluorescein isothiocyanate (FITC) (Abcam; ab3863), anti-VSVg (Abcam; ab50549), anti-CD81 (LifeSpan; LS-C359239), anti-CD81–FITC (Molecular Probes; A15753), anticalnexin (Cell Signaling; 2679), anticalreticulin (Cell Signaling; 12238), anti-UGCGL1 (NovoPro Laboratories; 116554), anti-PDI (Cell Signaling; 3501), anti-mouse antibody–Alexa Fluor 488 (Thermo Fisher; R37114), and anti-rabbit antibody–Alexa Fluor 594 (Thermo Fisher; A-21207).