ZAP-70 Zeta Chain Associated Protein Kinase 70 (CLL)

ZAP-70 is a cytoplasmic tyrosine kinase critical for T-cell receptor signaling. After antigen recognition it becomes activated and phosphorylates adaptor proteins, triggering downstream pathways that drive T-cell development, activation, proliferation, calcium mobilization and cytokine production. ZAP-70 function is essential for normal immune responses; altered expression or mutations can impair immunity and serve as a biomarker in certain lymphoid malignancies.

ZAP‑70 is a protein tyrosine kinase normally found in T cells; when abnormally expressed in CLL B cells it serves as a prognostic marker. High ZAP‑70 associates with unmutated IGHV, more aggressive disease, faster progression and poorer prognosis. It’s measured by flow cytometry and used with CD38 and IGHV mutation status to help stratify risk and guide monitoring/treatment decisions.

ZAP-70 is a cytosolic tyrosine kinase critical for T cell receptor signaling. After TCR engagement, Lck phosphorylates CD3 ITAMs, recruiting ZAP-70 via its SH2 domains. Activated ZAP-70 phosphorylates adaptor proteins like LAT and SLP‑76, assembling signalosomes that trigger calcium flux, MAPK, NF-κB and NFAT pathways. This drives T cell activation, proliferation, differentiation and cytokine production, and enables thymic selection.

Yes. ZAP‑70 levels must be balanced: loss or hypomorphic ZAP‑70 impairs thymic selection and regulatory T‑cell function, allowing autoreactive T cells to emerge; conversely, excess ZAP‑70 or hyperactive signaling lowers activation thresholds and drives exaggerated T‑cell responses. Both extremes disrupt immune tolerance and can contribute to autoimmune disease. Clinical and experimental data support this bidirectional risk.

ZAP‑70 gene mutations affect the ZAP‑70 tyrosine kinase, essential for T‑cell receptor signaling. Loss‑of‑function (usually autosomal recessive) mutations cause severe T‑cell immunodeficiency with absent or low CD8+ T cells, recurrent infections and failure to thrive. Separately, abnormal ZAP‑70 expression (not necessarily due to mutation) is used as a prognostic marker in chronic lymphocytic leukemia, indicating more aggressive disease.

Tyrosine kinases are enzymes that transfer a phosphate from ATP to tyrosine residues on proteins, initiating or modifying cell-signaling pathways. Receptor tyrosine kinases activate after ligand-induced dimerization and autophosphorylation, while nonreceptor kinases act in the cytoplasm. These phosphorylation events control growth, differentiation, metabolism, and survival; abnormal activity is linked to cancer and treated with specific inhibitors.