## **Core Concept**
The shelf life of gamma-irradiated packed red blood cells (pRBCs) is a critical consideration in transfusion medicine. Gamma irradiation is used to prevent graft-versus-host disease (GVHD) by inactivating lymphocytes. This process, however, affects the shelf life of the blood product.

## **Why the Correct Answer is Right**
Gamma irradiation of pRBCs inactivates T lymphocytes, which can cause GVHD. This process involves exposing the blood product to gamma radiation, which damages the DNA of the lymphocytes, preventing them from proliferating. The current standard for gamma irradiation reduces the shelf life of pRBCs to **35 days** from the date of irradiation, or the original expiration date, whichever comes first. This is because the irradiation process can cause some potassium leakage from the red cells, and there is a concern about the potential for bacterial contamination, albeit minimal.

## **Why Each Wrong Option is Incorrect**
- **Option A:** This option is incorrect because it does not accurately reflect the shelf life of gamma-irradiated pRBCs.
- **Option B:** This option suggests a longer shelf life than what is standard for gamma-irradiated pRBCs.
- **Option D:** This option suggests a shelf life that is too short compared to the standard.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that once gamma-irradiated, the **shelf life of pRBCs is reduced to 35 days**. This is crucial for transfusion services to manage inventory effectively and ensure patient safety.

## **Correct Answer:** . 35 days