Persistence of host Langerhans cells following allogeneic bone marrow transplantation: possible relationship with acute graft-versus-host disease.

Langerhans cells (LC) are bone marrow-derived dendritic antigen-presenting cells found in the epidermis. In an effort to determine the origin (host versus donor) of LC at different intervals following bone marrow transplantation, we performed skin biopsies in 16 recipients of sex-mismatched marrow. LC were identified using monoclonal antibody OKT6 in an indirect immunoperoxidase assay and their donor or host origin determined according to the presence or absence of Y body. The presence of Y-positive (donor) LC could be demonstrated in all (6/6) skin biopsies of female recipients of male marrow tested between days 39 and 730 post-transplant. Persistence of host LC in male recipients of female marrow was documented in all (6/6) recipients studied on day 39 and in two out of seven patients tested on day 120 post-transplant. From day 365 onward, no residual host LC could be detected, suggesting that by this time all epidermal LC are donor-derived. Our study demonstrates that host LC usually persist for 39 and up to 120 d following bone marrow transplantation. The relevance of this observation to the possible role of LC and other host dendritic antigen-presenting cells in the graft-versus-host reaction is discussed.