Answer:
The given blank can be filled with complement.
Step-by-step explanation:
The complement system refers to an array of proteins found in the normal plasma, which allows antibodies to eradicate bacteria. It is known as a complement as it helps in the antibacterial activity of the antibodies. In the complement system, the proteins present react with each other to combine with the pathogens and initiate an inflammatory cascade reaction to fight the infection.
The complement system acts against the pathogens in three ways. Initially, it stimulates a huge number of complement proteins, which combine with the pathogens so that they can get consumed by the phagocytes.
After that, the components of the complement proteins can function as chemoattractants to accommodate phagocytes. And lastly, the components of the complement system at the termination of the chain destruct the bacteria by creating holes in their membrane.