Which of the following type of hypersensitivity reactions is found in blood transfusion reaction
**Core Concept**
Type IV hypersensitivity reactions, also known as delayed-type hypersensitivity reactions, involve T-cell mediated immune responses. These reactions occur when sensitized T-cells recognize and bind to antigens, leading to the activation of various immune cells and the release of cytokines, resulting in tissue damage.
**Why the Correct Answer is Right**
In the context of blood transfusion reactions, Type IV hypersensitivity is the primary mechanism responsible for graft-versus-host disease (GVHD). GVHD occurs when T-cells from the donor's blood product recognize the recipient's antigens as foreign and mount an immune response, leading to tissue damage in the recipient. This reaction typically occurs 7-14 days after the transfusion. The involvement of T-cells and the delayed onset of symptoms are hallmarks of Type IV hypersensitivity reactions.
**Why Each Wrong Option is Incorrect**
**Option A:** Type I hypersensitivity reactions are immediate allergic reactions mediated by IgE antibodies and mast cells, which is not relevant to blood transfusion reactions.
**Option B:** Type II hypersensitivity reactions involve IgG or IgM antibodies binding to antigens on the surface of cells, leading to cell destruction, which is not the primary mechanism in blood transfusion reactions.
**Option C:** Type III hypersensitivity reactions are immune complex-mediated reactions, which involve the deposition of antigen-antibody complexes in tissues, leading to inflammation and tissue damage. While this can occur in some cases of blood transfusion reactions, it is not the primary mechanism.
**Clinical Pearl / High-Yield Fact**
It is essential to note that GVHD can occur even with allogenic blood transfusions, and the risk is higher in recipients who have received multiple transfusions or have a history of cancer. A thorough evaluation of the recipient's immune status and the donor's blood product is necessary to minimize the risk of GVHD.
**Correct Answer:** C. Type IV