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  In humans, FcγR receptors (FcγRI, FcγRIIa, FcγRIIb, FcγRIIc, FcγRIIIa, and FcγRIIIb) are widely expressed on immune cells, including macrophages, neutrophils, natural killer (NK) cells, eosinophils, basophils, and dendritic cells. These cell types exhibit distinct receptor expression profiles and participate in various effector functions, such as ADCC, to counteract viral entry into cells, as well as phagocytosis of antibody-virus immune complexes or infected cells.

      The functional relationship between receptors and cell types is complex, as the different actions of activating and inhibitory FcγRs modulate cellular effector functions. Receptors may also play additional roles in antigen presentation, B-cell activation and suppression, and potentially in HIV neutralization or suppression of infection in susceptible cells. Classic FcγRs comprise a family of cell surface receptors belonging to the immunoglobulin superfamily that are specific for IgG, with varying affinities, IgG subclass specificities, expressions, signaling mechanisms, and binding outcomes. FcγRIIb is an inhibitory receptor that includes the intracellular immunoreceptor tyrosine-based inhibitor (ITIM). FcγRIIIb is expressed exclusively on neutrophils and is anchored to the cell membrane via phosphatidylinositol; despite lacking an intracellular domain, FcγRIIIb is capable of triggering the release of reactive oxygen species, driving phagocytosis, and impairing FcγRIIa-mediated ADCC.

    FCGR2B TCR Activator CHO stably expresses FcγRIIb and aAPC in basal cells. FCGR2B TCR Activator CHO is used as a target cell for functional assays involving CD28 Effector Reporter Cells; a schematic diagram of this process is shown below.

Figure 1. Schematic diagram of the  FCGR2B/TCR Activator cell model

Cell Resuscitation
1)Rapidly thaw the frozen cells in a 37 °C water bath for approximately 60 seconds. Once thawed (which may take slightly less or more than 60 seconds), immediately transfer the cell suspension from the cryovial into a 15 mL centrifuge tube containing 10 mL of pre-warmed  CHO-K1 Human FCGR2B/TCR Activator Cell complete culture medium.
2)Centrifuge cells at 1000 rpm for 5 min to remove medium, then resuspend cells in 5 mL of pre-warmed complete medium.
3)Transfer the cell suspension into a T25 culture flask and incubate at 37 °C with 5% CO₂.
4)After approximately 24–36 hours, replace the medium or passage the cells to remove non-adherent dead cells.

Subculturing procedure
1)When the cell density reaches the appropriate confluency for passaging, wash the cells with PBS, then add 1 mL trypsin to detach the cells. When more than 80% of the cells detach upon gently tapping the culture flask, add complete culture medium to terminate digestion. Gently pipette to obtain a single-cell suspension, transfer to a 15 mL centrifuge tube, and centrifuge at 1000 rpm for 5 minutes.

2)Discard supernatant after centrifugation. Resuspend cells in fresh medium to a single-cell suspension and transfer to a new culture flask for continued growth.

Cell Freezing
After trypsinization and centrifugation of cells from each T75 flask or 10 cm culture dish, discard the supernatant. Add 2 mL of cryopreservation medium (90% FBS + 10% DMSO), gently resuspend thoroughly, and aliquot into two cryovials. Immediately place the cryovials into a controlled-rate freezing container (e.g., Nalgene 5100-0001), fill with isopropanol to the indicated level, and store at −80 °C. After 24 hours, transfer the cryovials to liquid nitrogen for long-term storage.