Alteration of CD20 protein expression on B-cell lymphoma cells during disease progression. (A) The clinical course of UPN 3 is depicted briefly. Large black arrows and smaller gray arrows indicate one course of combination chemotherapy with or without rituximab, respectively. Rituximab (375 mg/m2 each) was administered 7 times. During the patient's 24-month clinical course, tumor cells were harvested at stages I, II, and III from lymph nodes, bone marrow, peripheral blood, and/or cerebral fluid. (B) FCM analysis using anti-CD20 and anti-CD19 antibodies was carried out using tumor cells from peripheral blood. Positive cells are shown in the black lines, and the percentage of positive cells is shown. Note that CD20 expression was observed at the initial diagnosis (I, 84.3%), and that the expression then diminished after treatment with chemotherapy with rituximab (II, 7.1%). Interestingly, CD20 protein expression was observed again at the terminal stage after several chemotherapy treatments without rituximab (III, 76.4%). On the other hand, CD19 expression level was stable throughout the clinical course.
