Flow cytometry is the most widely used method for lymphocyte subset characterization. Two types of antibodies, directly labeled with fluorochrome, are currently used for immunological diagnosis of B-cell lymphoproliferation: monoclonal antibodies against leukocyte differentiation antigens and polyclonal antibodies against immunoglobulins and light chains. In this study is described the case of a patient with an uncommon immunophenotyping of a B-cell lymphoproliferative disorder. B-cells from peripheral blood and from bone marrow reacted positively with all the tested phycoerythrin (PE)-conjugated antibodies, including the isotypic control. So we thought about a B-cell proliferation carrying a surface receptor recognizing PE: these B-cells were directly labeled with streptavidin-PE, indeed. Moreover, the immunodots from the patient were able to fix the streptavidin-PE. Finally, this unusual immunophenotyping was solved by using antibodies labeled with other fluorochromes than PE.
(c) 2007 Clinical Cytometry Society