Detection of mixed chimerism and leukemic relapse after allogeneic bone marrow transplantation in subpopulations of leucocytes by fluorescent in situ hybridization in combination with the simultaneous immunophenotypic analysis of interphase cells.

Serial blood and marrow specimens from eight adult recipients of sex-mismatched transplants (BMT) for chronic myeloid leukemia (CML, n = 3), Ewing sarcoma (n = 1), acute myeloid leukemia (AML) in second remission (n = 1), acute lymphatic leukemia (ALL, n = 1) and multiple myeloma (n = 2) were analyzed by the simultaneous immunophenotypic CD3, CD4, CD8, CD20, CD34, CD10 and genotypic analysis (for X and Y chromosomes). This combined technique of moAb/APAAP staining for cell surface and cytoplasmic antigens and fluorescence in situ hybridization (FISH) for the detection of sex chromosomes allowed the qualitative and quantitative evaluation of mixed chimerism and/or relapse. Using the same slides for moAb/APAAP and FISH allowed the simultaneous identification of the cell lineage, the lymphocyte subpopulation and the genotype (XX or YX) in every blood or BM specimen analyzed. A mixed chimerism in the T cell (CD4, CD8+: median 26% host cells, range 5-44%) and in the myelomonocytic cell population (CD14+ median 16% host cells, range 5-50%) was observed at day +7 after BMT. By days +14 to +18 this mixed chimerism was reduced to 18% host T cells (range 5-50%) and 7% host myelomonocytic cells (range 0-20%). Beyond days +21 to +28 a stable donor chimerism for T cells, myelomonocytic cells and granulocytes was observed in seven of eight patients. Still 0.5-1% host cells of different lineages were detectable in five from the eight patients at later time points (> day + 100). In three patients with CML these cells were CD13 or CD13, CD34 positive and in one was CD4, CD8 positive.(ABSTRACT TRUNCATED AT 250 WORDS)