DETECTION OF CLONAL IMMUNOGLOBULIN GENE REARRANGEMENTS IN THE PERIPHERAL-BLOOD PROGENITOR CELLS OF PATIENTS WITH MULTIPLE-MYELOMA - THE POTENTIAL ROLE OF PURGING WITH CD34 POSITIVE SELECTION

Aims-To determine the extent of clonal cell contamination of periphera l blood progenitor cell. (PBPC) collections in patients with multiple myeloma (MM) and to assess the purging efficacy of CD34 positive selec tion. Methods-PBPC collections from 29 patients with MM were analysed for the presence of clonal immunoglobulin heavy chain (IgH) gene rearr angements with a fluorescence based PCR technique. In addition, the PB PC from eight of the 29 patients were ''purged'' by selection of CD34 positive haematopoietic progenitors with an avidin-biotin immunoabsorp tion column (Ceprate). In each case the unmanipulated PBPC, CD34 posit ive and waste fractions were all assessed for the presence of clonal I gH rearrangements. Results-Clonal IgH rearrangements (identical with t hose demonstrated in diagnostic bone marrow samples) were demonstrated in 10 (35%) of 29 cases and seemed to be confined to those with signi ficant residual bone marrow disease. Clonal rearrangements were eviden t in the PBPC of two of the eight patients who underwent CD34 selectio n; in both instances a ''clonal purge'' was seen as it was not possibl e to demonstrate the clonal rearrangement in the CD34 positive fractio n. In four of the six remaining cases the normal polyclonal fingerprin t could not be demonstrated in the CD34 positive fraction, which is co nsistent with a significant reduction in contaminating B cells. Conclu sions-Clonal cells contaminate PBPC collections in a significant propo rtion of patients with MM and may be eliminated by CD34 positive selec tion.