What if the new cells become the enemy of the body? A simple explanation of Graft vs. Host Disease (GvHD) after transplantation

Imagine that you have been given a stem cell transplant from a healthy person as a treatment for a disease like leukemia. This is expected to cure your condition. But very rarely, these new cells that came to help you, your body mistakes them for "enemy" and starts attacking your own cells. That's the complex situation we call "Graft versus Host Disease" or GvHD for short.

What is GvHD in simple terms?

To understand this, we need to know two words. "Graft" refers to the thing that is transplanted, that is, the healthy stem cells that are given to you from outside. "Host" refers to the host, that is, your body that receives those cells. So "Graft versus Host" means "graft versus host."

Typically, this type of stem cell transplant, called an allogeneic transplant, is done to treat cancers like leukemia and lymphoma, or bone marrow failure conditions like aplastic anemia . These transplanted cells are what start your body making new blood cells.

But, sometimes these new cells don't recognize your own cells. They think they're foreign invaders. So, they start attacking your healthy organs, like your skin, liver, and intestines. That's what GvHD is.

There are two main types of GvHD:

GvHD can be divided into two main types. In the past, this was divided according to the time of onset of symptoms. But now, doctors determine the exact type by looking at the symptoms, test results, and the time of onset of symptoms.

• Acute GvHD (aGvHD): This usually occurs within the first 100 days after the transplant. But it can sometimes occur later. This type mainly affects your skin, gastrointestinal system (intestines), and liver.
• Chronic GvHD (cGvHD): This type can occur at any time after a transplant, but is most common within the first two years . It can affect any part of the body, including the skin, mouth, liver, lungs, intestines, muscles, joints, and genitals.

A person who has had a transplant can develop one of these two types, both, or they can be healthy without any of them.

What are the symptoms of GvHD?

GvHD symptoms can range from very mild, through moderate, to severe, and even life-threatening. Let's take a look at the symptoms associated with these two types.

Why does this GvHD occur?

This is a bit scientific, but I'll explain it simply.

Normally, the cells of our immune system protect us from disease by fighting off foreign invaders like viruses and bacteria. But those cells never attack our own cells. The reason for this is that there is a special protein on the surface of all our cells. This is called Human Leukocyte Antigens (HLA) .

Except for identical twins, everyone's HLA is different.

When you get a stem cell transplant, the new blood cells that are made from those cells have the HLA of the person who donated the cells to you. If that HLA is too different from your HLA, those new cells look at the cells in your body and think, "This is an invader, his ID doesn't match ours." That's when those cells start attacking your body.

For this reason, doctors carefully check the donor and recipient's HLA to ensure they are as close as possible to each other before performing a transplant. But unless cells are taken from a twin, there is always some risk of GvHD.

Who is at higher risk of developing GvHD?

The most important risk factor is HLA incompatibility, but several other factors can also play a role.

Also, if you have already had Acute GvHD (aGvHD), you are at higher risk of developing Chronic GvHD (cGvHD).

How is this condition diagnosed and treated?

Diagnosis

Your doctor will diagnose GvHD by doing a physical exam, looking at your symptoms, and doing blood tests and a biopsy. A biopsy involves taking a small piece of skin or affected tissue and examining it under a microscope. Because some of the symptoms of chronic GvHD are similar to other conditions, your doctor will rule out other conditions before diagnosing GvHD.

Treatment

To prevent GvHD after a transplant, you will be given immunosuppressive medications that suppress your immune system. These medications work by reducing the ability of foreign cells to attack your body.

• For acute GvHD (aGvHD): Often, corticosteroids are given as pills, injections, or as a cream applied to the skin. If these do not control the disease, other drugs such as Ruxolitinib (Jakafi®) or clinical trials may be considered.
• For Chronic GvHD (cGvHD): Long-term immunosuppressive drugs are also given for this. If the condition is not controlled by these, drugs such as Ruxolitinib (Jakafi®), Belumosudil (Rezurock™), Ibrutinib (Imbruvica®) or specialized treatments such as photopheresis may be required.

Side effects of treatment

These treatments suppress your immune system, which reduces your body's ability to fight infections. This increases your risk of developing fungal, bacterial, and viral infections. Your doctor will also prescribe medications to help prevent these potentially life-threatening infections.

Other effects that may occur due to GvHD

Is GvHD life-threatening?

Yes, GvHD can be life-threatening. Chronic GvHD, in particular, is the leading cause of death after a stem cell transplant, other than the primary disease. That's why it's important to discuss the risks with your doctor before undergoing any treatment.

Is there any benefit from GvHD?

Surprisingly, yes. GvHD has some benefits. These new immune cells that attack your healthy cells also seek out and destroy any cancer cells that may be left in your body. This is called the "graft-versus-tumor effect." Therefore, studies have shown that patients who develop GvHD are less likely to have their cancer return.

Things you can do for your safety

Your doctor will explain how you should take care of yourself after the transplant. Be especially careful about these things if you are at risk for GvHD.

• Protect yourself from the sun: Sun exposure can worsen GvHD. So wear long-sleeved shirts and long pants when going outside. Use a sunscreen with at least SPF 50.
• Oral hygiene: Brush your teeth thoroughly to reduce the risk of gum disease.
• Food and Drink: Avoid spicy, oily, and foods that can cause mouth ulcers.
• Protect yourself from germs: Since your immune system is weak, avoid places where diseases are spread and crowded places. Always keep your hands clean.

When should I see the doctor?

It is important to notify your doctor immediately if you notice any changes in your body, especially signs of infection or a fever of 38 degrees Celsius (100.4 Fahrenheit) or higher. Infections can become more serious quickly when you are taking medications that suppress the immune system.

Your doctor will monitor you regularly after your transplant to watch for complications such as GvHD. If symptoms develop, they will change your medications or prescribe new ones. It is very important to take all prescribed medications as directed and follow your doctor's instructions.

Graft vs. Host Disease, GvHD, stem cell transplant, allogeneic transplant, bone marrow transplant, bone marrow transplantation, GvHD symptoms