ICOSLG Knockout THP-1 Cell Line

The ICOSLG Knockout THP-1 Cell Line is a CRISPR/Cas9-edited knockout cell line derived from the THP-1 human monocytic leukemia cell line, engineered to disrupt the expression of the ICOSLG gene. This cell line provides a stable loss-of-function model for investigating ICOSLG-mediated co-stimulatory signaling in antigen-presenting cell (APC)-T cell interactions. By eliminating ICOSLG, researchers can systematically study the role of this immune checkpoint ligand in T cell activation, differentiation, and cytokine production without the transient effects or off-target concerns associated with antibody blockade or RNA interference. The knockout cell line offers a homogeneous genetic background suitable for reproducible functional assays, enabling precise dissection of the ICOS/ICOSLG axis in both normal and pathological immune responses.

THP-1 is a well-characterized human monocytic leukemia cell line originally isolated from the peripheral blood of a patient with acute monocytic leukemia. It is widely used as a model for monocyte and macrophage biology due to its capacity to differentiate into macrophage-like cells upon stimulation with phorbol esters. Differentiated THP-1 cells upregulate surface markers such as MHC class II and costimulatory molecules, rendering them competent for antigen presentation and T cell stimulation. The cell line is a standard platform for studying cytokine secretion, phagocytosis, inflammatory signaling, and immune cell crosstalk, making it particularly relevant for investigations of innate and adaptive immune mechanisms.

ICOSLG encodes the inducible co-stimulatory ligand, a transmembrane protein expressed on APCs that binds the ICOS receptor on activated T cells. This interaction triggers downstream signaling cascades, prominently including the PI3K/AKT pathway, which promotes T cell proliferation, survival, and effector functions. ICOSLG engagement also activates NF-??B signaling, leading to transcriptional upregulation of cytokines such as IL-4, IL-10, and IL-21 that drive T follicular helper (Tfh) cell differentiation and B cell class switching. Upstream regulators including TNF-??, IL-1, CD40L, and NF-??B induce ICOSLG expression, while ICOSLG-mediated signals modulate mTOR and NFAT transcriptional programs. The ICOSLG knockout in THP-1 cells disrupts this co-stimulatory node, impairing the ability of APCs to deliver critical secondary signals that shape T cell fate and humoral immunity.

In the context of THP-1 cells, the loss of ICOSLG creates a specific deficiency in co-stimulatory capacity that mimics defective APC-T cell communication observed in autoimmune disorders and immunodeficiencies. THP-1 cells naturally express low levels of ICOSLG, which is upregulated upon activation; knockout of this gene therefore provides a clean background to assess the contribution of ICOSLG to T cell responses in co-culture systems. This model is particularly valuable for dissecting the distinct contributions of co-stimulatory versus antigen-presentation signals, as THP-1 cells can still present antigens via MHC class II. The knockout line enables researchers to investigate how loss of ICOSLG affects T helper cell polarization, cytokine profiles, and downstream B cell functions, offering insights into diseases such as systemic lupus erythematosus, rheumatoid arthritis, and common variable immunodeficiency.

The ICOSLG Knockout THP-1 Cell Line supports a broad range of research applications, including T cell co-stimulation assays, immune checkpoint studies, and cancer immunotherapy modeling. Co-culture experiments with primary T cells combined with flow cytometric analysis of activation markers (e.g., CD69, ICOS) and ELISA-based quantification of secreted IL-4, IL-10, or IL-21 provide functional readouts of APC activity. RT-qPCR and western blotting can be employed to examine the expression of downstream signaling components such as PI3K, AKT, and mTOR, while NFAT luciferase reporter assays enable high-throughput screening of co-stimulatory signals. This model also facilitates investigation of autoimmune disease mechanisms and transplantation rejection by assessing the impact of ICOSLG loss on Tfh cell development and B cell help. For further details or technical inquiries, please contact Ascent Research.