Memory B cells producing somatically mutated antiphospholipid antibodies are present in healthy individuals

• Published in: Blood Vol. 102; no. 7; pp. 2459 - 2465
• Main Authors: Lieby, Patricia, Soley, Anne, Knapp, Anne-Marie, Cerutti, Martine, Freyssinet, Jean-Marie, Pasquali, Jean-Louis, Martin, Thierry
• Format: Journal Article
• Language: English
• Published: Washington, DC Elsevier Inc 01.10.2003; The Americain Society of Hematology; American Society of Hematology
• Subjects: Adolescent; Adult; Antibodies, Anticardiolipin - genetics; Antibodies, Anticardiolipin - immunology; Antibodies, Monoclonal - immunology; B-Lymphocytes - immunology; Biological and medical sciences; Cellular Biology; Female; Flow Cytometry; Fundamental and applied biological sciences. Psychology; Fundamental immunology; Gene Rearrangement, B-Lymphocyte - immunology; Humans; Immunobiology; Immunologic Memory - genetics; Immunologic Memory - immunology; Immunophenotyping; Infectious Mononucleosis - immunology; Life Sciences; Lymphoid cells: ontogeny, maturation, markers, receptors, circulation and recirculation; Male; Gammaherpesvirinae; Diphosphatidylglycerol; Human; Healthy subject; Antibody; Herpesviridae; Autoantibody; Phospholipid; B-Lymphocyte; Epstein Barr virus; Infectious mononucleosis; Memory lymphocyte; Infection; Virus; Immunological investigation; Viral disease; Mutation
• DOI: 10.1182/blood-2003-01-0180
• ISSN: 0006-4971

Antiphospholipid antibodies (aPLs) are associated with thrombosis and recurrent abortions during autoimmune pathologies, but they are also produced in healthy individuals and during infectious diseases. To analyze the possible links between physiologic and pathologic aPLs, it is of importance to characterize normal aPL production. We took advantage of the known tropism of Epstein-Barr virus (EBV) for B cells in general, and memory B cells in particular, during primary infectious mononucleosis (IMN) in 3 patients to get access to anticardiolipin (aCL)-producing B cells. Flow cytometry analysis of these cells showed that, depending on the patient, 10% to 60% of immunoglobulin M (IgM) aCL-producing B cells express the CD27 marker of memory B cells. Single cell sorting of aCL B cells, followed by single cell reverse transcription-polymerase chain reaction (RT-PCR) amplification of their immunoglobulin variable region genes, showed that some of these cells produce mutated forms of aCL antibodies, confirming their memory B-cell origin. Considering that, during primary IMN, EBV infects and expands already pre-existing memory B cells, we conclude that healthy individuals have a discrete pool of aCL memory cells able to produce mutated forms of antibodies. The implications of this new information are discussed in light of different hypotheses regarding the origin of aCL. (Blood. 2003;102:2459-2465)