Cytokine Release Syndrome during Antithymocyte Globulin/Anti-T Lymphocyte Globulin Serotherapy for Graft-versus-Host Disease Prophylaxis before Allogeneic Hematopoietic Stem Cell Transplantation: Incidence and Early Clinical Impact According to American Society of Transplantation and Cellular Therapy Grading Criteria

•Cytokine release syndrome (CRS) according to ASTCT grading was a frequent (58%) but mostly mild (92% grade 1-2) complication during antithymocyte globulin/anti-T lymphocyte globulin serotherapy for graft-versus-host disease (GVHD) prophylaxis.•Even mild CRS resulted in a pronounced systemic inflammatory response, indicated by high levels of C-reactive protein, IL-6, and procalcitonin.•Acute GVHD grade II-IV until day +180 was associated with CRS grade 3-4 in multivariate analysis.