Antithymocyte globulin (ATG)
Say it: an-tee-THY-moh-site GLOB-yoo-lin · Brand names: Atgam, Thymoglobulin
Antithymocyte globulin is a medicine made of antibodies that lowers the number of T cells to calm the immune system.
What it is
This medicine is made by giving human immune cells to horses or rabbits, then collecting the antibodies they make. These antibodies attach to T cells, a type of white blood cell, and remove them from the blood. This calms an immune system that is attacking the bone marrow or a transplant.
Often used for
- severe aplastic anemia (horse ATG, Atgam)
- preventing and treating kidney transplant rejection (rabbit ATG, Thymoglobulin, and Atgam)
- preventing graft-versus-host disease before some stem cell transplants
How you get it
ATG is given as a slow drip through a vein (IV), usually in the hospital. Each dose takes about 4 to 8 hours. It is often given once a day for 3 to 5 days. Your schedule may be different.
Common side effects and what helps
- Fever, chills, or shaking during the drip. You will get medicines before each dose to help.
- Rash or itching.
- Low white blood cells and platelets. Your team will check your blood counts every day.
- Headache or muscle aches.
- Nausea. Tell your nurse if you feel sick.
- Feeling tired. Rest when you need to.
Call your care team right away if you have
- During the drip: trouble breathing, swelling of the face or throat, chest tightness, or feeling faint. Tell your nurse right away.
- About 1 to 2 weeks later: fever, rash, joint pain, or swelling. This can be a reaction called serum sickness.
- A fever of 100.4 degrees Fahrenheit (38 degrees Celsius) or higher, or chills
- Unusual bleeding or bruising
- Cough, sore throat, painful urination, or other signs of infection
Before you start, tell your team
- If you are pregnant, may become pregnant, or are breastfeeding
- If you have ever had a reaction to horse or rabbit products, or to ATG before
- If you have an infection now
- All the medicines, vitamins, and herbal products you take
Good to know
- Serious allergic and infusion reactions can happen. You will be watched closely in the hospital. For horse ATG, your team may do a skin test first.
- Serum sickness can happen 1 to 2 weeks after treatment. Steroids are often given to prevent or treat it.
- It weakens your immune system for months. Your team may give medicines to prevent certain infections, and will check for viruses such as CMV.
- You will have blood tests every day during treatment to check your blood counts.
- Ask your team before getting any live vaccine.
Questions to ask
- Which type of ATG will I get, horse or rabbit?
- What medicines will I get to prevent reactions?
- What signs of serum sickness should I watch for after I go home?
- How long will my immune system be weak?
Part of these treatment plans
Side effect guides
- Fatigue (tiredness)
- Nausea and vomiting
- Low white blood cells and infection risk
- Low platelets and bleeding
- Skin rash (including EGFR-inhibitor rash)
Sources
Quick answers
- What is Antithymocyte globulin (ATG)?
- Antithymocyte globulin is a medicine made of antibodies that lowers the number of T cells to calm the immune system. Brand names: Atgam, Thymoglobulin.
- What is Antithymocyte globulin (ATG) used for?
- severe aplastic anemia (horse ATG, Atgam); preventing and treating kidney transplant rejection (rabbit ATG, Thymoglobulin, and Atgam); preventing graft-versus-host disease before some stem cell transplants.
- How is Antithymocyte globulin (ATG) given?
- ATG is given as a slow drip through a vein (IV), usually in the hospital. Each dose takes about 4 to 8 hours. It is often given once a day for 3 to 5 days. Your schedule may be different.
- What are the common side effects of Antithymocyte globulin (ATG)?
- Fever, chills, or shaking during the drip. Rash or itching. Low white blood cells and platelets. Headache or muscle aches. Nausea. Feeling tired.
- When should I call my care team while taking Antithymocyte globulin (ATG)?
- During the drip: trouble breathing, swelling of the face or throat, chest tightness, or feeling faint. Tell your nurse right away; About 1 to 2 weeks later: fever, rash, joint pain, or swelling. This can be a reaction called serum sickness; A fever of 100.4 degrees Fahrenheit (38 degrees Celsius) or higher, or chills; Unusual bleeding or bruising; Cough, sore throat, painful urination, or other signs of infection.
- Which chemotherapy plans include Antithymocyte globulin (ATG)?
- ATG and cyclosporine.
Last updated: 2026-10-27. Medically reviewed by Veli Bakalov, MD, medical oncologist (October 2026). General education from Step by Step, the patient portal of HemeOncBuddy.