The CD40LG Knockout HAP1 Polyclonal Cells represent a CRISPR/Cas9-edited polyclonal knockout cell population carrying a targeted disruption of the human CD40LG gene in the near-haploid HAP1 cell line. This product provides a genetically defined loss-of-function model in which CD40 ligand (CD154) expression is abolished, enabling rigorous investigation of CD40?CCD40LG signaling without residual wild-type gene activity. The polyclonal format offers a heterogeneous population of knockout cells, reflecting the diversity of CRISPR-edited alleles and providing a robust tool for pooled functional genomics screens, biochemical pathway analyses, and immunology-focused phenotypic assays. Researchers can employ this system to dissect cellular mechanisms dependent on CD40LG-mediated intercellular communication, including T cell?CB cell collaboration, co-stimulatory signaling, and adaptive immune regulation. The cells are suitable for downstream applications such as flow cytometry, co-culture assays, reporter gene experiments, and transcriptomic profiling, making them a versatile resource for both hypothesis-driven and discovery-based studies.
The host HAP1 cell line is a near-haploid chronic myeloid leukemia (CML) model originally derived from the KBM-7 line, characterized by an adherent growth morphology and a predominantly haploid karyotype that simplifies genetic manipulation and phenotypic interpretation. Its hematopoietic lineage background provides a context for studying immune-related signaling, while the near-haploid genome reduces complexities associated with diploid gene redundancy, enhancing the sensitivity of loss-of-function phenotypic readouts. HAP1 cells maintain intact core signaling machinery, including members of the TNF receptor-associated factor (TRAF), NF-??B, and mitogen-activated protein kinase (MAPK) families that are central to CD40LG-dependent pathways. Although not of lymphoid origin, the HAP1 line expresses key components of the CD40 signaling axis upon appropriate stimulation, making it a tractable model for exploring molecular interactions downstream of CD40 engagement when CD40-expressing target cells are introduced in co-culture systems or ectopically expressed.
CD40LG encodes CD40 ligand (CD154), a type II transmembrane protein of the tumor necrosis factor (TNF) superfamily that is transiently expressed on activated CD4+ T cells and, to a lesser extent, on other immune cells. Its binding to the CD40 receptor on B cells, dendritic cells, and macrophages initiates receptor trimerization and recruitment of adaptor proteins TRAF1, TRAF2, TRAF3, TRAF5, and TRAF6, which differentially activate downstream cascades. Canonical NF-??B signaling is driven primarily through TRAF2 and TRAF6, leading to I??B kinase (IKK) complex activation, phosphorylation and degradation of I??B, and nuclear translocation of NF-??B dimers such as p65/p50. Concurrently, MAPK pathways??including JNK, p38, and ERK??are stimulated, with TRAF proteins bridging CD40 to MAP3Ks. These signals converge on transcriptional programs that upregulate activation-induced cytidine deaminase (AICDA), promote immunoglobulin class switching and somatic hypermutation, and enhance B cell survival via BCL2 family members. Upstream, CD40LG expression is tightly controlled by T-cell receptor engagement, CD28 costimulation, and cytokines such as IL-4 and IL-21, with transcription factors NFAT and AP-1 playing critical roles.
Disruption of CD40LG in the HAP1 polyclonal knockout cells eliminates functional CD40 ligand, thereby preventing productive CD40 activation on co-cultured target cells and abolishing the TRAF-mediated signaling cascades that transduce CD40 engagement. This engineered model recapitulates key features of X-linked hyper-IgM syndrome, a primary immunodeficiency in which CD40LG mutations impair cognate T cell help, leading to defective germinal center formation, impaired antibody class switching, and heightened susceptibility to opportunistic infections. In the HAP1 background, the knockout serves as a clean null background for evaluating CD40LG-dependent processes without the confounding influence of endogenous CD40 ligand. It facilitates the dissection of cell-autonomous versus non-autonomous roles, particularly when combined with CD40-expressing reporter cells or primary B cells. The haploid genetics of HAP1 additionally enable straightforward interpretation of gene dose effects and reduce the likelihood of compensatory mutations that can arise in diploid knockout models, making this system especially valuable for CRISPR-based synthetic lethality screens and drug?Ctarget validation studies in immune signaling contexts.
Typical research applications include modeling X-linked hyper-IgM syndrome in cellular assays, elucidating the molecular requirements for T cell?CB cell immunological synapse formation, and screening for small molecules that modulate CD40?CCD40LG interactions or restore downstream signaling in immunodeficiency. The cells are amenable to flow cytometric analysis of CD40LG surface expression, co-culture with B cells followed by ELISA for secreted antibodies, NF-??B luciferase reporter assays to quantify pathway activity, and western blotting for phosphorylated I??B and p65. Quantitative PCR for AICDA transcripts can directly assess the impact on class-switch recombination components. Additionally, they can be employed in arrayed or pooled CRISPR screens to identify synthetic lethal partners of CD40LG or modulators of NF-??B and MAPK cascades. For further details on assay compatibility or custom engineering requests, please contact Ascent Research.
