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    ICOS is a co-stimulatory receptor that is induced upon T-cell activation, while ICOSL is its ligand, which is primarily constitutively expressed on the surface of B cells and antigen-presenting cells. The core mechanism of action for both lies in the fact that when activated T cells (particularly follicular helper T cells) migrate to lymphoid follicles and encounter B cells, the binding of ICOS to ICOSL provides a critical co-stimulatory signal to the T cells, This primarily occurs through the activation of downstream pathways such as PI3K, driving T-cell proliferation, survival, and cytokine production (e.g., IL-21), thereby precisely regulating the germinal center response. Ultimately, this promotes antibody affinity maturation and class switching in B cells, leading to the generation of highly effective humoral immunity.

ICOSL aAPC CHO, as the target cell for the ICOS Effector Reporter Cell, effectively mimics the in vivo ICOS signaling pathway; the mechanism is illustrated in the figure below.

Figure 1. ICOSL aAPC CHO 细胞模型原理图

Figure 2. Recombinant ICOSL aAPC CHO stably expressing ICOSL.

Figure 3. Blocking of ICOSL induced ICOS Effector Reporter Cell(C3) Activity by ICOSL Blocking Ab with ICOSL aAPC CHO(C42).

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 ICOSL aAPC 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.