[1431] Abnormalities of Immunoglobulin Light Chain Protein Expression in Mature B-Cell Lymphomas/Leukemias

F Sayedian, V Douglas-Nikitin, M Smith, AM Blenc, G Fan, JZ Huang. William Beaumont Hospital, Royal Oak, MI; Oregon Health & Science University, Portland, OR

Background: The majority of mature B-cell lymphomas or leukemias express surface immunglobulin light chains (kappa or lambda). About 3-12% of mature B-cell lymphomas or leukemias do not express surface immunoglobulin light chains. It is not clear whether it is due to absence of light chain protein production or due to production of abnormal light chain protein.
Design: Cytoplasmic light chain expression patterns were studied with flow cytometry using both monoclonal and polyclonal antibodies in 88 cases of surface light chain negative mature B-cells lymphomas/leukemias. These cases included 76 cases of chronic lymphocytic leukemias/small lymphocytic lymphomas (CLL/SLL), 9 cases of diffuse large B-cell lymphomas (DLBCL), 2 cases of follicular lymphomas (FL) and 2 cases of Burkitt lymphomas (BL).
Results: The study revealed that 82 cases (93.2%) of surface light chain negative mature B-cell lymphomas showed cytoplasmic light chain expression. Three cases (3.4%) (1 DLBCL, 1 CLL and 1 BL) had cytoplasmic light chain expression detected by polyclonal antibodies but not by monoclonal antibodies. Six (6.8%) of them (3 DLBCL, 1 CLL, 1 FL, and 1 BL) showed neither surface nor cytoplasmic light chains detectable with either polyclonal or monoclonal antibodies.
Conclusions: This study demonstrated that the vast majority of surface light chain negative B-cell lymphomas/leukemias have intracellular light chain production. There appears to be three forms of abnormal expressions of light chain proteins in mature B-cell lymphomas/leukemias: failure of externalization (surface negative, cytoplasmic positive), alteration of light chain protein structure leading to loss of antigen epitopes (recognized by polyclonal antibodies, but not by monoclonal antibodies) and a complete lack of light chain production (neither surface nor cytoplasic light chains detected with polyclonal antibodies). Further studies are indicated to investigate the underlying genetic mechanisms.
Category: Hematopathology

Monday, March 22, 2010 1:00 PM

Poster Session II # 148, Monday Afternoon


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