Specificity: Recognizes human ZAP-70, a 70kD tyrosine protein kinase which associates with the T-cell receptor (TCR) zeta chain and undergoes phosphorylation following TCR stimulation. ZAP-70 is primarily expressed in T lymphocytes and natural killer cells, where it plays a key role in T-cell receptor (TCR) signalling. Recent studies suggest that ZAP-70 is also expressed in a population of normal immature B-cells and in B-cells from a sub-set of patients with chronic lymphocytic leukemia