Question

Which of the following statements can be related to Arthus reaction?
A. It is a type of III hypersensitivity reaction.
B. Activation of complement leads to vasodilation.
C. It was first observed in cow
D. Only A and B

Answer 1

Hint:The complement system which is also known as complement cascade
It is a part of the immune system that enhances the ability of antibodies and phagocytic cells to clear microbes and damaged cells from an organism which further promote inflammation and attack the pathogen's cell membrane.

Complete answer:
 In order to answer this question, we need to know Arthus' reaction.
Arthus reaction: An Arthus reaction is a local vasculitis (Inflammation of blood vessels) associated with deposition of immune complexes and activation of complement.
Immune complexes: An immune complex sometimes called an antigen-antibody complex or antigen-bound antibody is a molecule formed from the binding of multiple antigens to antibodies.
Hypersensitivity reaction I: Immediate Hypersensitivity also known as Anaphylactic Reaction.
These allergic reactions are systemic or localized (e.g., hives, wheal and erythema reactions).
Hypersensitivity reaction II: It is a Cytotoxic Reaction (Antibody-dependent).
Hypersensitivity reaction III: It is an Immune Complex Reaction.
The excess of antigen agglutination leads to the formation of small immune complexes which are not cleared from the circulation.
Arthus reaction is caused due to the formation of antigen antibody complex which causes an inflammatory response.
Serum sickness is also caused due to hypersensitivity created by antigen - antibody complex.
Hypersensitivity reaction IV: It is a Cell-Mediated or Delayed Hypersensitivity Reaction.
So, Arthus reaction is related to the Hypersensitivity reaction III and activation of complement which further leads to vasodilation.

So, the correct answer is option D. Both A and B.

Note: Anaphylaxis is a serious, life-threatening allergic reaction. The most common anaphylactic reactions are to foods, insect stings, medications and latex.
If you are allergic to a substance, your immune system overreacts to this allergen by releasing chemicals that cause allergy symptoms.
Risk factors are asthma and allergen.
It is a type I hypersensitivity reaction.