What does MASP-2 cleave in the immune system?

MASP-2, or MBL-associated serine protease-2, plays a crucial role in the complement system, particularly in the lectin pathway of complement activation. This pathway is initiated when lectins such as mannose-binding lectin (MBL) bind to specific carbohydrate patterns on pathogens. Once MBL is bound to its target, MASP-2 becomes activated and subsequently cleaves proteins involved in the complement cascade.

In this context, the correct function of MASP-2 is to cleave C2 and C4. Cleavage of C2 produces C2a and C2b, while cleavage of C4 leads to C4a and C4b. The products C4b and C2a then combine to form the C3 convertase (C4b2a), which is essential for the amplification of the complement system, leading to opsonization of pathogens, recruitment of inflammatory cells, and formation of the membrane attack complex.

By understanding the specific roles of MASP-2 in processing these particular components, you can appreciate its vital contribution to the innate immune response and complement activation.