Cell Kinetic Analysis of Interleukin-2 Receptors in Chronic Lymphocytic Leukemia using the AgNOR Silver Stain.

¹Hanaa A El-Aggan and ²Tallat A El-Atti.

¹Haematology Department, Medical Research Institute and ²Internal Medicine Department, Faculty of Medicine, Alexandria University.

B-cell chronic lymphocytic leukemia (B-CLL) is typically a low grade neoplasm with a diploid DNA index and low proliferative activity. Interleukin-2 receptor (IL-2 R/CD₂₅) positivity often indicates increased proliferative activity and activation in both T and B lymphocytes. The argyrophilic nucleolar organizer regions (AgNORs) are loops of DNA identified by a silver staining technique and have been correlated with ploidy and proliferative activity. Two AgNOR counting methods have been previously shown to correlate with DNA ploidy and proliferative activity. The mean AgNOR count (mAgNOR) correlates more with ploidy and the percentage of nuclei with ³5 AgNORs / nucleus (pAgNOR) reflects proliferative activity. Bone marrow specimens were obtained from 20 patients with newly diagnosed B-CLL, they were subjected to AgNOR silver stain and expression of IL-2R (CD₂₅). All tumors were CD₅₊, CD₁₉₊, CD₂₀₊. Ten tumors were IL-2R -ve (< 20%, IL-2R + B cells) and 10 were IL-2R +ve (³20%, IL-2R + B cells). There was also a preponderance of l light chain expression in the IL-2R +ve tumors (7/10) compared with IL-2R -ve cases (3/10). Except for one case, all tumors had mAgNOR counts within the diploid range (<2.4). The ten IL-2R -ve tumors had pAgNOR in the range of 1% to 7% (mean 3.5±2.12%), whereas the IL-2R +ve tumors had significantly higher pAgNOR ranging from 6 to 15% (mean 10.9±2.99%) p < 0.001. This finding suggests that IL-2R +ve B-CLL might represent a subgroup of tumors with higher proliferative activity. Also the study indicates that silver staining technique could reliably be used as an alternative method of cell kinetic analysis when the material available is not suitable for assessment by other methods such as flow cytometry, Ki_-67 labeling index or IL-2R expression. It is a simple, cheap and available to every laboratory.