Early Indus Valley Civilization ... their Geograhpy, their customs and Indo-Aryan civilization with the earliest caste system.
Antibodies contribute to immunity in three main ways: they can prevent pathogens from entering or damaging cells by binding to them; they can stimulate removal of a pathogen by macrophages and other cells by coating the pathogen; and they can trigger direct pathogen destruction by stimulating other immune responses such as the complement pathway.
Antibodies are proteins produced by the immune system that bind to a target antigen on the cell surface. The immune system normally uses them to fight pathogens. Each antibody is specific to one or a few proteins. Those that bind to tumor antigens treat cancer. Cell surface receptors are common targets for antibody therapies and include CD20, CD274 and CD279.