## **Core Concept**
Graft-versus-host disease (GVHD) is a major complication of bone marrow transplantation, where the transplanted graft attacks the host's tissues. Prevention of GVHD involves immunosuppressive strategies to reduce the reactivity of the graft against the host. Various methods are employed to mitigate this risk.

## **Why the Correct Answer is Right**
The correct answer, **T-cell depletion**, is a method used to prevent GVHD. T-cells are the primary effectors of GVHD. By depleting T-cells from the donor graft, the risk of GVHD decreases significantly. This can be achieved through various techniques, including the use of monoclonal antibodies that target T-cells.

## **Why Each Wrong Option is Incorrect**
- **Option A:** While certain drugs can be used to prevent GVHD, the specificity and directness of T-cell depletion make it a more targeted approach.
- **Option B:** This option is not directly related to a commonly recognized method for preventing GVHD.
- **Option D:** Although immunosuppressive drugs can help manage GVHD, they are not as specific or preventive as T-cell depletion.

## **Clinical Pearl / High-Yield Fact**
A key clinical pearl is that T-cell depletion significantly reduces the risk of GVHD but may also increase the risk of graft failure and infections due to the impaired immune reconstitution. Therefore, the decision to use T-cell depletion must be balanced against these potential risks.

## **Correct Answer:** . T-cell depletion