Posttransplantation After hematopoietic stem cell transplantation, recipients are given colony-stimulating factors to shorten duration of posttransplantation leukopenia, prophylactic anti-infective drugs, and, after allogeneic hematopoietic stem cell transplantation, up to 6 months of prophylactic immunosuppressants (typically methotrexate and cyclosporine) to prevent donor T cells from reacting against recipient HLA molecules (graft-vs-host disease).