Besides specific cellular-mediated T cell responses, B cell related humoral responses have been demonstrated during the course of graft-versus-host disease after semiallogeneic transplantation of cellular antigen. Following semiallogeneic small bowel transplantation, there are, besides others, two specific forms of antigen-presenting cells, namely sinus lining cells (SLCs) and follicular dendritic cells (FDCs) which mediate primary and secondary humoral immune responses, respectively. This study was aimed to clarify the role of these dendritic cell entities after transplantation of small bowel grafts in a one-sided graft-versus-host (GvH) model for untreated and immunosuppressed (15-deoxyspergualin) recipient animals. As graft-versus-host disease progressed, SLCs and FDCs were eliminated in donor and recipient graft-versus-host associated target tissues (spleen and mesenteric lymph nodes) of untreated animals, whereas these dendritic cells prevailed in immunosuppressed recipients. 15-deoxyspergualin successfully prevented GvHD and significantly prolonged the mean survival time of untreated rats (16.0 +/- 4.5 d) for at least 21 d. Based on the immunosuppressive efficacy of 15-deoxyspergualin on the survival and function of SLCs and FDCs, an unaltered development of germinal centers and B cell proliferation within mesenteric lymph nodes and spleen was maintained.