Page 24 - GPD-3-2

Gene & Protein in Disease Review of CAR-T in ADs

antigen with high affinity and is used to stimulate CAR improving their proliferation and persistence. Fourth-
signaling and T-cell activation. Hinges derived from generation CARs, compared with third-generation CARs,
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CD8, CD28, IgG1, or IgG4 are flexible segments that integrate an activated T cell-nuclear factor transcription
overcome spatial hindrance, allowing CAR to transmit response element. After CAR-T cells recognize target
signals and recognize T cell activation. Transmembrane antigens, they activate downstream transcription factors
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domains from CD3ζ, CD28, CD4, and CD8α not only and stimulate the production of cytokines, which improve
serve to anchor the antigen-binding domain to the cell T cell survival rates and recruit and activate other immune
membrane but also play a crucial role in the activity of cells. Fifth-generation CARs are created by combining
CAR. The intracellular co-stimulatory domain includes an IL-2 receptor chain fragment (IL-2R) with a second-
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the activation and co-stimulatory domains, and common generation CAR. The JAK-STAT signaling pathway
co-stimulatory domains include CD28 and 4-1BB is activated by the downstream signaling pathway of
(CD137) (Figure 1). 28,29 IL-2R. Furthermore, when CAR-T cells detect antigens,
the antigen-specific activation of receptors activates all
2.2. Development of CAR downstream signaling pathways, resulting in full T cell
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To enhance the antitumor efficacy of CAR-T cells while activation and increased therapeutic agent persistence.
mitigating T-cell activation-associated cytotoxicity, CAR Fifth-generation CARs are also classified as universal CARs
technology targeting intracellular signaling pathways (UCARs), as their fabrication is based on gene editing
has been developed. The activation of T cells requires technology to prevent human rejection. They can also be
two signaling pathways. First, the TCR-CD3 complex pre-prepared for allogeneic T cells before administration
recognizes the MHC/antigenic peptide complex and but may still face clearance due to immune rejection
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transmits the specific recognition signal. Second, non- and may induce graft-versus-host disease. Third- and
specific co-stimulatory signals are provided by APC fourth-generation CAR-T cells exhibit increased tumor-
co-stimulatory molecules. The first generation of CAR killing capacities and cytotoxicity but are presently in
contained solely the CD3ζ intracellular domain, limiting the research and development stage. Second-generation
CAR-T cell activation and proliferation in vivo. Second- CARs, characterized by their milder approach, are widely
generation CARs feature two co-stimulatory domains, employed in tumor therapy, representing the majority of
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CD3ζ, along with either CD28 or 4-1BB (CD137), listed CAR-T products (Figure 2).
enhancing stimulation signals. These dual co-stimulatory
domains enable the CAR-T cells to proliferate extensively 3. Research progress of CAR-T in ADs
and sufficiently produce cytokines. The increased The use of CAR-T cell therapy for ADs primarily involves
expression of anti-apoptotic factors leads to the CAR-T three different mechanisms: (i) CAR-T cells recognize
cells exhibiting a longer survival time and a more durable specific antigens in target cells and initiate cytotoxic
therapeutic effect. Third-generation CARs, in addition to activity against those cells. For example, CAR-T cell
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CD3ζ, have two co-stimulatory domains, such as CD28, therapy targeting B cell CD19 is used in the treatment of
CD4, ICOS, 1-137BB (CD40), or OX134 (CD3), which SLE. After infusion into the body of the patient, the CD19
provide T cells with more effective anti-tumor effects CAR-T cells undergo expansion and specifically target
while increasing their cytokine production ability and and eliminate CD19-expressing B cells, thereby reducing

A B

Figure 1. Flowchart of CAR T cell preparation (A) chimeric antigen receptor (CAR) comprising an antigen-binding region (scFv region) made up of
heavy and light variable chains, a hinge region, a transmembrane domain, and an intracellular co-stimulatory domain. (B) CAR-T cell production process
involves the extraction of peripheral blood from a patient, isolation, and activation of T cells, transfection of T cells with the CAR gene, expansion of
CAR-T cells in vitro, and infusion back into the body of the patient.

Volume 3 Issue 2 (2024) 3 doi: 10.36922/gpd.2851