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CD28 is a core co-stimulatory receptor on the surface of T cells, belonging to the immunoglobulin superfamily (IgSF). It provides the 'second signal' (co-stimulation) for T cell activation by binding to ligands CD80 (B7-1) and CD86 (B7-2) on antigen-presenting cells (APCs), serving as a key regulatory node in adaptive immune responses. Deficiency in CD28 signaling leads to T cell anergy, while excessive activation is associated with autoimmune diseases and graft-versus-host disease (GVHD). In tumor immunotherapy, restoring CD28 co-stimulatory signaling can enhance the efficacy of CAR-T cells or PD-1 inhibitors, making it an important target for immune modulation.

  
Activation of CD28-mediated co-stimulation in T cells initiates signaling cascades that lead to the activation and nuclear translocation of transcription factors AP-1 and NFκB. These pathways significantly boost the production of T cell cytokines, particularly IL-2, thereby promoting T cell proliferation, differentiation, and survival.

The Jurkat E6.1 Human CD28 Effector Reporter Cell model effectively mimics the in vivo MET signaling transduction process. The principle is illustrated in the figure below.

Figure 1. Schematic diagram of the Jurkat E6.1 Human CD28 Effector Reporter Cell model.

Figure 2. Dose Response of CD28 Agonist Ab in CD28 Effector Reporter Cell(C11) with FCGR2B TCR Activitor CHO Cell,(C18).

Cell Passage Procedures

1.This cell line grows in suspension.
2.Upon receipt, cells should be thawed immediately or stored in liquid nitrogen until use.
3.Before thawing, pre-warm the water bath and culture medium to 37 °C, and prepare a small amount of dry ice.
4.Remove the cryovial from storage and transport it to the cell culture laboratory on dry ice.
5.Rapidly thaw the cells in a 37 °C water bath. Once the cells are completely thawed, spray the cryovial with 70% ethanol for disinfection and transfer it to a biosafety cabinet.
6.Add 10 mL of pre-warmed culture medium into a 15 mL centrifuge tube. Transfer the contents of the cryovial into the tube and centrifuge at 1000 rpm for 5 minutes.
7.Carefully discard the supernatant. Resuspend the cell pellet in 5 mL of pre-warmed culture medium by gentle pipetting. Immediately perform cell counting and adjust the cell density to 3–6 × 10⁵ cells/mL based on the counting results, then transfer the cells into a culture flask.
8.Count the cells every 1–2 days. When the cell density exceeds 1 × 10⁶ cells/mL, passage the cells promptly or add fresh culture medium. Maintain the cell density between 2 × 10⁵ and 1 × 10⁶ cells/mL.

Suspension Cell Cryopreservation Procedure:

1.Collect 8 × 10⁶ cells, centrifuge, and discard the supernatant.
2.Add 1 mL of cell freezing medium (90% FBS + 10% DMSO) and gently pipette to mix thoroughly. Transfer the suspension into a cryovial.
3.Immediately place the cryovial into a controlled-rate freezing container (Nalgene 5100-0001), fill with isopropanol up to the indicated level, and store at −80 °C.
4.After 24 hours, transfer the cryovial to liquid nitrogen for long-term storage.