Final answer:
MHC class III gene complex encodes complement proteins that are crucial for innate immune defense mechanisms. MHC contains genes coding for glycoproteins on the surface of all nucleated cells, and the complement system is part of this complex.
Step-by-step explanation:
Complement proteins are encoded by genes in the MHC class III gene complex. The major histocompatibility complex (MHC) is a collection of genes coding for glycoprotein molecules expressed on the surface of all nucleated cells. MHC proteins play a crucial role in the immune response.
The class III region of the MHC contains genes that encode various components of the complement system, an innate immune defense mechanism. These proteins are involved in enhancing the ability of antibodies and phagocytic cells to clear microbes and damaged cells, promoting inflammation, and attacking the pathogen's cell membrane. Hence, the correct answer to the question is "C. III".