Use of Tocilizumab (TCZ) to prevent acute graft versus host disease (GVHD)

This study tests whether giving a single dose of tocilizumab (a drug that reduces immune activity) before a stem cell transplant can prevent graft-versus-host disease (GVHD). GVHD is a serious complication where the donor's immune cells attack the transplant recipient's body. Tocilizumab blocks a specific inflammatory signal and may reduce this reaction. You may be eligible if: - You are 18 to 65 years old - You are having a matched stem cell transplant (from a matched sibling or unrelated donor) - Your general health is good enough for transplant (ECOG score below 2) - Your heart, lungs, liver, and kidneys are functioning adequately You may NOT be eligible if: - You have had a solid tumor in the last 2 years (skin cancers are acceptable) - You are HIV, hepatitis B, or hepatitis C positive - You are pregnant or breastfeeding - You have had serious bowel complications such as diverticulitis with abscess - You have allergies to similar biologic medications Talk to your doctor about whether this trial might be right for you.