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Interleukin 22 (IL-22) is a member of the IL-10 cytokine family and an emerging CD4+ T-cell cytokine that plays a crucial role in antimicrobial defense, homeostasis, and tissue repair. This family also includes other cytokines such as IL-10, IL-19, IL-20, IL-24, IL-26, and type III interferon (IFNλ). IL-22 is a cytokine primarily secreted by lymphocytes, including those of both the innate and adaptive immune systems, such as type 3 innate lymphoid cells (ILC3), αβT cells, γδT cells, and NKT cells. In the absence of obvious infection or inflammation—that is, in a steady state—the primary source of IL-22 is ILC3, which is abundantly present in the mucosa of the large and small intestines. Among αβ T cells, IL-22 is primarily produced by Th1, Th17, and Th22 cells; approximately 33% of IL-22-producing CD4+ T cells are Th1 cells, 50% are Th22 cells, and 15% are Th17 cells. Neutrophils can also produce IL-22.

      The functional IL-22R is a heterodimer composed of IL-22R1 and IL-10R2; IL-10R2 is shared with various cytokine receptor complexes of the IL-10 family. IL-10R2 is widely expressed, whereas IL-22R1 is expressed only in epithelial cells of the bronchi, liver, pancreas, and intestine, as well as in stromal cells. In the liver, hepatocytes express both IL-10R2 and IL-22R1; Many diseases, such as psoriasis, graft-versus-host disease, liver and pancreatic injury, ulcerative colitis, and tumors, are closely associated with IL-22.

Upon binding of IL-22 to its receptor, the Jak1/Tyk2 kinase is activated, leading to the phosphorylation of these receptors and the transcription activators STAT1, STAT3. STAT3 induces the expression of numerous genes involved in various signaling pathways, including those related to apoptosis and the cell cycle. In addition to STAT signaling, the IL-22-IL-22R1-IL-10R2 complex also leads to the activation of the MAPK and p38 pathways.

 The IL-22 Effector Reporter Cell model effectively mimics the in vivo signaling pathway of IL-22; the mechanism is illustrated in the figure below.

Figure 1. Schematic diagram of the IL-22 Effector Reporter Cell model

Figure 2. Recombinant IL22 Effector Reporter Cell constitutively expressing IL22R1.

Figure 3. Recombinant IL22 Effector Reporter Cell constitutively expressing IL10R2.

Figure 4.Dose Response of Recombinant Human IL-22 in IL22 Effector Reporter Cells(C8).

Figure 5.Inhibition of rhIL22-induced Reporter Activity by Fezakinumab in IL22 Effector Reporter Cell(C8).

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  HEK293 Human IL22 Effector Reporter 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.