Tracking the follicular lymphoma cells in flow cytometry: characterisation of a new useful antibody combination.

Objectives: Follicular lymphoma (FL) is the most common adult non-Hodgkin's lymphoma. Diagnosis is based on morphology and can be confirmed by cytogenetic, flow cytometry (FCM) or molecular studies. Despite all these complementary approaches, diagnosis sometimes remains difficult. The purpose of the present work was to characterise the expression of new specific follicular cells markers which allows us to target specifically the abnormal FL cell population in FCM. Methods: A total of 153 samples from healthy subjects and from patients with chronic B-cell lymphoproliferative disorders were analysed by FCM in the same conditions for purpose of comparison. Results: We showed that CD44 is weakly expressed in FL cells compared with peripheral blood mononuclear cell from normal blood donors and others cells from B lymphoproliferative diseases. We nevertheless observed bone marrow samples where some immature B-cell population express CD44 with lower fluorescence intensity. Therefore, we developed a double antibody combination, using CD44 and CD38, which allowed us to separate the normal immature cells from the pathological population using FCM. Conclusion: This new phenotypic approach offers an accurate (sensitivity and specificity of 93% and 96%, respectively), fast and low sample consuming method for the diagnosis of FL.