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TITLE: THE DETECTION AND QUANTITATION OF IgH MONOCLONALITY IN BONE MARROW TRANSPLANT RECIPIENTS

David Senitzer,¹ Laima Gaidulis.<sup>1

1</sup>Hematology and Bone Marrow Transplantation, City of Hope National Medical Center, Duarte, California

Immunoglobulin heavy–chain (IgH) gene rearrangements are common in B–cell neoplasias and also occur during the development of normal B–cell lineages. Studies have shown that monitoring IgH rearrangements can serve as a useful marker for the effectiveness of clinical treatment in B cell malignancies, such as Multiple Myeloma. We propose to use this marker to monitor relapse in patients transplanted for various hematologic malignancies. We used a sensitive PCR amplification technique to detect monoclonality in DNA extracted from 19 patients and their donors (normal control). Sample DNA was obtained prior to and post BMT from bone marrow aspirates or from peripheral blood. Primers to the conserved framework region FR3, together with a consensus JH primer fluorescently labeled with FAM, were used to amplify the CDR3 (third complimentary determining region) region of the IgH. The PCR products were electrophoresed on an ABI 377 Sequencer and analyzed with Genescan. We were able to detect monoclonal peaks in 8/19 patient samples (42 %) prior to transplant and in two samples of patients who had relapsed post transplant. The other 13 samples, as well as all donors, showed a heterogenous, polyclonal pattern indicative of the normal state. The monoclonal PCR products ranged in size from 82–127 bp and were detected in 3 patients with relapsed ALL, 1 AML, 1 CML in blast crisis, and 2 Multiple Myeloma patients. IgH rearrangements were also analyzed at day 30 post–transplant in 16 patients. With one exception, 15/16 samples showed a depressed and immature clonal development although all were fully engrafted (100 % donor cells) as demonstrated by short tandem repeat analysis (STR). In those patients where we were able to test subsequent samples, 3/5 showed a reappearance of the pre transplant polyclonal pattern at day 60 post–transplant while the other 2 still maintained their immature and atypical pattern. Infectious complications remain a significant problem in post BMT associated morbidity and mortality. Monitoring the recovery of the IgH rearrangements may be useful for the management of the patient post transplant.