+**C4b** is a pivotal protein fragment within the body's [Complement system](/wiki/Complement_system), a crucial part of innate immunity. Formed from the cleavage of [Complement component 4](/wiki/Complement_component_4), it serves as an anchor on microbial surfaces, signaling the start of a cascade to clear pathogens.
+## See also
+- [Complement activation](/wiki/Complement_activation)
+- [Classical pathway](/wiki/Classical_pathway)
+- [Immune system](/wiki/Immune_system)
... 1 more lines