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

Verified step by step guidance

1. Understand that the complement system is part of the immune response and involves proteins that, when activated, split into fragments with different functions.
2. 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.
3. Recall that among these, C5a is considered the most potent inflammatory mediator, but C3a and C4a also contribute to inflammation to varying degrees.
4. Analyze the options given: C3a, C4a, C5a, and 'all of the above' to determine which fragments have inflammatory roles.
5. Conclude that since all three fragments (C3a, C4a, and C5a) have inflammatory properties, the correct answer involves recognizing their collective role in inflammation.

Key Concepts

Complement System Overview

The complement system is a group of proteins that enhance immune responses by promoting inflammation, opsonization, and cell lysis. It is activated via classical, lectin, or alternative pathways, leading to the cleavage of complement proteins into active fragments with distinct functions.

Anaphylatoxins and Inflammation

Anaphylatoxins are small complement fragments (C3a, C4a, C5a) that trigger inflammation by inducing mast cell degranulation, increasing vascular permeability, and attracting immune cells. Among these, C5a is the most potent inflammatory mediator.

Roles of C3a, C4a, and C5a

C3a, C4a, and C5a are cleavage products with varying inflammatory effects. C3a and C5a strongly promote inflammation, with C5a being the most powerful chemoattractant, while C4a has weaker inflammatory activity. Understanding their differences is key to answering which fragment is inflammatory.