The HLA-A Knockout HAP1 Polyclonal Cells are a CRISPR/Cas9-edited polyclonal knockout cell population in which the HLA-A gene has been disrupted in the near-haploid human HAP1 cell line. This polyclonal population carries a heterogeneous array of loss-of-function mutations across the HLA-A locus, resulting in profound impairment of surface MHC class I expression. The knockout model eliminates the dominant source of classical MHC class I molecules in HAP1 cells, providing a clean background for studying peptide presentation and immune recognition.
HAP1 is a chronic myeloid leukemia-derived cell line with a near-haploid karyotype, originally isolated from the KBM-7 line. Its haploid nature simplifies genetic analysis and knockout studies, as disruption of a single allele leads to a functional null phenotype for most genes. HAP1 cells grow adherently, maintain a stable genome, and are widely employed in CRISPR-based functional genomics screens, protein interaction proteomics, and drug target validation.
The HLA-A gene encodes an MHC class I heavy chain that forms a heterodimer with ??2-microglobulin in the endoplasmic reticulum. This complex is loaded with 8-10 amino acid peptides derived from intracellular proteins, a process assisted by the peptide-loading complex components tapasin, calreticulin, ERp57, and the transporter associated with antigen processing (TAP1/TAP2). Once transported to the cell surface, the HLA-A?Cpeptide complex is recognized by the T cell receptor (TCR) on CD8+ cytotoxic T lymphocytes, triggering immune responses against infected or transformed cells. HLA-A expression is transcriptionally upregulated by interferon-?? (IFN-??) through the IRF1 and NLRC5 signaling pathways, and is also modulated by NF-??B and TNF-??. In addition to engaging TCRs, surface HLA-A serves as a ligand for killer-cell immunoglobulin-like receptors (KIRs) on natural killer (NK) cells, which can inhibit or activate NK cytotoxicity via missing-self recognition.
In the HAP1 background, knockout of HLA-A eliminates classical MHC class I surface expression, rendering the cells resistant to CD8+ T cell-mediated killing but potentially more susceptible to NK cell attack due to loss of inhibitory signals. This dichotomy makes the polyclonal knockout population an ideal tool for dissecting mechanisms of immune evasion, allograft rejection, and the balance between T cell and NK cell surveillance. The model also facilitates investigation of antigen-processing machinery components, as the absence of HLA-A allows direct assessment of peptide generation and transport pathways without confounding surface expression.
Applications include flow cytometry-based monitoring of MHC class I expression, co-immunoprecipitation assays with ??2-microglobulin to study complex assembly, CD8+ T cell cytotoxicity and degranulation assays, and functional screening of compounds that modulate antigen presentation or NK cell ligands. The cells are suitable for IFN-?? stimulation experiments to probe signaling upstream of MHC class I, as well as for viral immune escape studies where pathogens downregulate surface HLA. This product supports research in transplantation immunology, autoimmune disease modeling (e.g., ankylosing spondylitis, psoriasis), and drug hypersensitivity screening. For further details, please contact Ascent Research.
