OPTIMIZATION OF IMMUNOHISTOCHEMICAL DETECTION OF P-GLYCOPROTEIN IN CHRONIC LYMPHOID DISORDERS

To optimize the immunohistochemical detection of the multidrug resista nce (MDR)-associated P-glycoprotein (P-gp) in chronic lymphoid disorde rs, the authors compared the sensitivity of three different monoclonal antibodies (MoAb) directed against P-gp (C219, JSB-1, and MRK 16) by using the APAAP technique on four tissue preparations obtained from ly mphoid tumors: Cryostat sections, ModAMEX processed sections, frozen c ytospin preparations, and fresh cytospin preparations. Tumor samples w ere obtained from patients with previously treated chronic lymphocytic leukemia (6 cases) or non-Hodgkin's malignant lymphoma (4 cases). Lym ph nodes (n = 9), spleen (n = 3), and blood (n = 5) were analyzed. JSB -1 MoAb detected P-gp in 4 of 12 cases (33.3%) on either frozen sectio ns or ModAMEX processed sections, and in 6 of 17 cases (35.3%) on froz en cytospin preparations. The sensitivity of JSB-1 was significantly i mproved when fresh cytospin preparations were used with an incidence o f P-gp positive samples as high as 70.6% (P <.05). C219 MoAb was unrea ctive with lymphoid cells whatever the technique used, whereas this an tibody stained stromal cells. MRK 16 MoAb was equally reactive to JSB- 1 on fresh cytospin preparations, but unreactive when the other prepar ations were used. The specificity of JSB1 MoAb was confirmed by both W estern blot analysis and Rhodamine 123 efflux assay. The authors used JSB-1 MoAb on fresh cytospin smears prepared from 28 CLL patients. Ove rall incidence of P-gp positive cases was 39.2%. Univariate analysis s howed that P-gp expression was correlated with prior therapy, refracto riness to treatment, Rai stratification, and time of tissue storage af ter diagnosis. The authors recommend the use of JSB-1 on fresh cytospi n preparations for the immunocytochemical detection of P-gp in chronic lymphoid disorders.