Cell responsible for ‘Graft versus host disease;’ (GVHD) is:
**Core Concept**
Graft-versus-host disease (GVHD) is a complication of allogenic hematopoietic stem cell transplantation, where the immune cells from the donor (graft) recognize the recipient's tissues as foreign and react against them. This reaction is mediated by T lymphocytes.
**Why the Correct Answer is Right**
The correct answer is T lymphocytes, specifically cytotoxic T cells, which recognize and destroy the recipient's cells through cell-mediated immunity. In GVHD, the donor's T cells are activated by the recipient's major histocompatibility complex (MHC) molecules, leading to an immune response against the recipient's tissues. This process involves the recognition of the recipient's MHC class I and II molecules by the donor's T cells.
**Why Each Wrong Option is Incorrect**
**Option A:** Macrophages are involved in the innate immune response and do not play a primary role in GVHD.
**Option B:** B lymphocytes are responsible for humoral immunity and the production of antibodies, but they are not the primary cells involved in GVHD.
**Option C:** Dendritic cells are antigen-presenting cells that play a role in the initiation of the immune response, but they are not the cells responsible for the pathology of GVHD.
**Clinical Pearl / High-Yield Fact**
GVHD is a significant complication of allogenic hematopoietic stem cell transplantation and can occur after other types of solid organ transplants. It is essential to monitor patients closely for signs of GVHD, such as skin rash, liver dysfunction, and gastrointestinal symptoms.
**Correct Answer: C. T lymphocytes.