FLOW CYTOMETRIC ANALYSIS OF KAPPA-LIGHT AND LAMBDA-LIGHT CHAIN EXPRESSION IN EVALUATION OF SPECIMENS FOR B-CELL NEOPLASIA

Analysis of light chain expression is one of the most important determ inations in flow cytometric immunophenotyping of patient specimens. Nu merous technical factors, such as antibody choice and cytophilic antib ody artifact, impact a laboratory's ability to perform this test. Ther e have been conflicting reports concerning the efficacy of polyclonal versus monoclonal antibodies, as well as methods of circumventing cyto philic antibodies, indicating that a consensus has not been reached on optimal methods for light chain determination. The authors have inves tigated methods for light chain analysis in 104 normal donors and 366 patient specimens, comparing different anti-light chain antibodies as well as strategies for analysis of specimens with low numbers of monoc lonal B cells, admired polyclonal B cells, or cytophilic antibodies. T he patient specimens were either part of the initial diagnostic evalua tion of patients with suspected lymphoma, or were performed for stagin g or assessment of treatment of patients with known B-cell neoplasia. No monoclonality was detected in control specimens, and there was no s ignificant difference in staining with monoclonal verses polyclonal an ti-light chain antibodies. In addition, cytophilic antibody did not ob scure results in normal controls. Monoclonality was detected in 106 pa tient specimens, with 89 showing gross involvement with a predominant monoclonal B-cell process. However, in 43% of the grossly monoclonal s pecimens, there was failure to detect monoclonality with at least one light chain antibody set, with 8% of these cases showing failure with two anti-light chain sets. This indicates the importance of antibody c hoice in light chain analysis. Cytophilic antibody artifact in monoclo nal specimens was easily overcome by appropriate antibody combinations , obviating the need for cytophilic antibody-shedding by incubation at 37 degrees C in fetal calf serum. In 27 patient specimens with low nu mbers of B cells or admired polyclonal B cells, a clonal search based on FSC and CD19 or CD20 expression was performed. In 17 of the 27 case s (63%), a small monoclonal population was detected among admired poly clonal B cells. The authors conclude that multiple strategies are nece ssary in flow cytometric analysis for B-cell monoclonality. (C) 1996 W iley-Liss, Inc.