Immunohistochemical analysis of ZAP-70 expression in chronic lymphocytic leukemia

This paper shows a protocol for the detection of ZAP-70 expression in B-CLL (B cell chronic lymphocytic leukemia) tumor cells by common immunohistochemical methods. The study was conducted on bone marrow trephine biopsies from 62 B-CLL patients at the time of diagnosis. Immunohistochemical reactions based on peroxidase and alkaline phosphatase reactions were used, as well as double immunofluorescent labeling for ZAP-70 detection as an indirect marker of mutated and unmutated CLL. Clinical relevance of the ZAP-70 expression detection method was assessed using chi2 test between ZAP-70 positivity data and other known prognostic factors, i.e., clinical and cytogenetics data. ZAP-70 was detected in 13 out of 62 patients. Statistically significant results were obtained for ZAP-70 positive cases and known indicators of worse prognosis. Immunohistochemical analysis supported by double immunofluorescent labeling, as shown here, is an easy and reliable technique for the detection of ZAP-70 expression in B-CLL tumor cells applicable in every hematopathology laboratory.