Zeta Chain Associated Protein

Overview

Zeta chain associated protein (ZAP-70) is a non-receptor tyrosine kinase expressed primarily in T cells and natural killer cells that associates with the zeta chain of the T cell receptor complex. It plays a critical role in T cell signaling by phosphorylating downstream adaptor proteins following antigen recognition, leading to T cell activation, proliferation, and cytokine production. Low ZAP-70 expression in chronic lymphocytic leukemia (CLL) B cells indicates an unmutated IgVH status and aggressive disease, while high expression correlates with mutated IgVH and indolent disease. Clinically, ZAP-70 measurement by flow cytometry serves as a prognostic biomarker in CLL, predicting treatment need and survival independent of other risk factors.

Clinical Use Cases

  • Prognostication in early-stage chronic lymphocytic leukemia (CLL).
  • Risk stratification for CLL patients with Rai stage 0-II disease.
  • Prediction of time to first treatment and overall survival in CLL.
  • Assessment of IgVH mutation status surrogate in CLL.

Specimen Types

  • Peripheral blood (EDTA).
  • Bone marrow aspirate.
  • Lymph node biopsy (formalin-fixed tissue for IHC).

Measurement Methods

  • Flow cytometry (intracellular staining on CLL B cells).
  • Immunohistochemistry (tissue sections).
  • Quantitative PCR (mRNA expression).
  • Western blot (research applications).

Test Preparation and Influencing Factors

  • No special patient preparation required.
  • Sample processing within 24 hours critical for flow cytometry viability.
  • Leukemic cell purity affects results; CD19+/CD5+ gating standard.
  • Tyrosine kinase inhibitors may alter expression.
  • Prior therapy or Richter transformation changes expression patterns.
  • Cut-off threshold (20% positive CLL cells) laboratory-specific.

Synonyms

  • ZAP-70.
  • Tyrosine-protein kinase ZAP-70.
  • 70 kDa zeta-associated protein.

Further Reading