Which of the complement fragments is inflammatory?
a. C3a
b. C4a
c. C5a
d. All of the above

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Understand that the complement system is part of the immune response and involves proteins that, when activated, split into fragments with different functions.

Recognize that certain complement fragments, specifically C3a, C4a, and C5a, are known as anaphylatoxins because they promote inflammation by increasing vascular permeability and attracting immune cells.

Recall that among these, C5a is considered the most potent inflammatory mediator, but C3a and C4a also contribute to inflammation.

Since the question asks which fragment is inflammatory, consider whether the answer includes one or all of these fragments based on their known roles.

Conclude that because C3a, C4a, and C5a all have inflammatory properties, the correct choice would be the option that includes all of them.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Complement System

The complement system is a group of proteins in the blood that helps the immune system clear pathogens. It is activated through a cascade, producing fragments that have various roles such as opsonization, cell lysis, and inflammation.

Anaphylatoxins (C3a, C4a, C5a)

Anaphylatoxins are small complement fragments (C3a, C4a, C5a) generated during complement activation. They promote inflammation by inducing smooth muscle contraction, increasing vascular permeability, and attracting immune cells to infection sites.

Role of C5a in Inflammation

C5a is the most potent anaphylatoxin, strongly attracting neutrophils and other immune cells to infection sites. It enhances inflammation by stimulating the release of histamine and other mediators, making it a key player in the inflammatory response.

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