Answer;
-Antibodies
Step-by-step explanation;
-Antibodies, also known as immunoglobulins,are large Y-shaped proteins produced by B- cells and used by the immune system to identify and neutralize foreign objects such as bacteria and viruses. Antibodies are produced by B cells, and are either secreted into circulation or remain expressed on the surface of the B cell.
-Circulating antibodies are produced by clonal B cells that specifically respond to only one antigen. Antibodies contribute to immunity in three ways: preventing pathogens from entering or damaging cells by binding to them; stimulating removal of pathogens by macrophages and other cells by coating the pathogen; and also triggering destruction of pathogens by stimulating other immune responses such as the complement pathway.