Immune complex Hypersensitivity reaction is- rpt
**Core Concept**
Immune complex hypersensitivity reactions involve the formation of antigen-antibody complexes that deposit in tissues, leading to activation of complement and release of pro-inflammatory mediators, resulting in tissue damage and inflammation.
**Why the Correct Answer is Right**
In an immune complex hypersensitivity reaction, the binding of antibodies to antigens forms large complexes that are not soluble and can deposit in various tissues, including the kidneys, skin, and joints. This deposition activates the complement system, which leads to the release of pro-inflammatory mediators such as C5a, C3a, and bradykinin, causing vasodilation, increased vascular permeability, and leukocyte recruitment to the site of inflammation. This results in tissue damage and inflammation.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it refers to a type I hypersensitivity reaction, which is mediated by IgE antibodies and involves the release of histamine from mast cells, leading to allergic symptoms such as itching, hives, and anaphylaxis.
**Option B:** This option is incorrect because it refers to a type II hypersensitivity reaction, which is mediated by IgG and IgM antibodies that bind to cell surface antigens, leading to antibody-dependent cellular cytotoxicity (ADCC) and complement-dependent cytotoxicity (CDC).
**Option C:** This option is incorrect because it refers to a type III hypersensitivity reaction, which is mediated by IgG and IgM antibodies that form immune complexes in the absence of inflammation, and is not related to tissue damage.
**Clinical Pearl / High-Yield Fact**
Immune complex hypersensitivity reactions can be triggered by infections, such as systemic lupus erythematosus (SLE), or by exposure to certain medications, such as penicillin or hydralazine, and can cause a range of symptoms, including fever, arthritis, and nephritis.
**Correct Answer: D. Immune complex hypersensitivity reaction involves the formation of antigen-antibody complexes that deposit in tissues, leading to activation of complement and release of pro-inflammatory mediators, resulting in tissue damage and inflammation.