The CD4 Knockout HAP1 Polyclonal Cells are a CRISPR/Cas9-engineered polyclonal knockout cell population designed to abolish CD4 gene function. The polyclonal format contains a heterogeneous mix of edited cells harboring various disruptive mutations, collectively ensuring reliable loss of expression. This product provides a firm experimental foundation for dissecting CD4-related processes in hematopoietic models, immunology, and virology.
HAP1 is a near-haploid human cell line derived from the KBM-7 chronic myeloid leukemia line. Its haploid karyotype (with a small disomic region) makes it exceptionally tractable for gene knockout studies, as targeting a single allele yields a null phenotype. HAP1 retains key features of hematopoietic progenitors and is extensively used for genetic screening, signaling pathway analysis, and protein function studies.
The CD4 protein functions as a co-receptor for the T cell receptor (TCR) complex, binding to MHC class II molecules on antigen-presenting cells to amplify TCR signaling. CD4 interacts with the TCR/CD3 complex and recruits the Src-family kinase Lck, which phosphorylates ITAMs on CD3 chains, leading to Zap70 activation. Downstream signals propagate through LAT, PLC??1, and MAP kinases to activate transcription factors NFAT and NF-??B, ultimately driving IL-2 gene expression. CD4 expression is regulated by LEF1/TCF transcription factors downstream of Notch and IL-7 signaling. Beyond adaptive immunity, CD4 is the primary receptor for HIV-1, specifically binding the gp120 envelope protein to facilitate viral entry.
In the HAP1 background, the CD4 knockout provides a reductionist platform to study CD4-dependent signaling and HIV-1 entry mechanisms. Although HAP1 is of myeloid lineage and does not endogenously express TCR components, its genetic simplicity allows for straightforward reconstitution experiments. By ectopically expressing CD4 along with TCR??/?? and CD3 chains, researchers can rebuild the CD4 signaling module and assess proximal activation events such as Lck recruitment and Zap70 phosphorylation in a controlled manner. The near-haploid state eliminates concerns about allelic compensation, ensuring clear phenotypic readouts in functional complementation assays.
Key applications include HIV-1 infectivity assays using pseudotyped reporter viruses to measure viral entry efficiency, T cell activation assays quantifying IL-2 secretion or NFAT-driven reporters, and studies of autoimmune disease mechanisms examining CD4?CMHC-II interactions. The knockout population is also suitable for drug screening targeting gp120 binding or Lck kinase activity. Routine validation via flow cytometry for CD4 surface expression, western blotting for protein levels, and RT-qPCR for transcript analysis ensures accurate phenotypic assessment. For more information, please contact Ascent Research.
