COMBINED IMMUNOPHENOTYPING AND FISH WITH SEX CHROMOSOME-SPECIFIC DNA PROBES FOR THE DETECTION OF CHIMERISM IN EPIDERMAL LANGERHANS CELLS AFTER SEX-MISMATCHED BONE-MARROW TRANSPLANTATION

Langerhans cells (LC) of the skin represent bone marrow-derived dendri tic antigen-presenting cells and are therefore important in pathophysi ological processes such as rejection, graft-versus-host disease, and g raft-versus-leukemia-reaction after bone marrow transplantation (BMT). For understanding of these diseases, the evaluation of the chimeric s tatus of LC following BMT is of great interest. To analyze the sex chr omosome constitution of LC in the skin, we established a modified and refined technique of combined immunophenotyping and fluorescence in si tu hybridization (FISH) and investigated frozen sections of skin biops ies from nine patients after allogeneic sex-mismatched BMT and of two healthy donors for control. LC were specifically labeled using a fluor escent CD1a antibody and hybridized simultaneously with X and Y chromo some-specific DNA probes. The results of this practical application on nine leukemia patients show the appearance of donor-type LC and the p ersistence of host-type LC at various times (36 up to 1395 days) after sex-mismatched BMT. Complete chimerism of LC could not be detected in any case. The frequency of recipient-specific LC ranged from 7% to 92 % and showed no correlation with time postgrafting. We conclude from o ur results of 1461 analyzed LC that combined immunophenotyping and int erphase cytogenetic analysis by FISH is the method of choice for the a ssessment of chimerism in a particular cell type after sex-mismatched BMT. Its practical application on other tissues affected by BMT-relate d pathophysiological processes reveals further knowledge of the time-d ependent course of chimeric patterns after BMT.