Julian Zipfel, Matthias Eyrich, Paul-Gerhardt Schlegel, Verena Wiegering

• B cells and DCs are suspected to play an important role in the pathogenesis of cGvHD, which is a serious complication of HSCT with high morbidity. It is characterized by immune responses of donor immune cells against recipient-derived antigens. athogenesis is not yet fully understood, however reconstitution of B cells after HSCT has similarities to physiologic ontogeny. Immunophenotyping and co-cultivation-experiments of B cells and DCs from pediatric patients with cGvHD as well as healthy donors were conducted. Significant differences betweenB cells and DCs are suspected to play an important role in the pathogenesis of cGvHD, which is a serious complication of HSCT with high morbidity. It is characterized by immune responses of donor immune cells against recipient-derived antigens. athogenesis is not yet fully understood, however reconstitution of B cells after HSCT has similarities to physiologic ontogeny. Immunophenotyping and co-cultivation-experiments of B cells and DCs from pediatric patients with cGvHD as well as healthy donors were conducted. Significant differences between patients and healthy donors were observed with increased memory, transitional, CD69+ and CD86+ phenotype and lower levels of naïve B cells due to apoptosis. Co-cultivation revealed this to be primarily B cell-dependent without major effects of and with DCs. There was a decreased CD11c- phenotype in patients and less apoptosis of DCs. Our data suggest a disturbed homeostasis in B cells with increased memory phenotype in patients, whereas DCs could not influence these differences, therefore DCs are not imposing as promising targets. B cell-dependent approaches should be further investigated.…