Which process provides immunity against antigens and pathogens in the body fluids?

The answer is humoral immunity.

Humoral immunity is immunity found in the body fluids. It is mediated by macromolecules, such as antibodies, complement proteins, and other proteins. Humoral immunity protects extracellular spaces. Antibodies are produced by B-cells and are responsible for a destruction of pathogens present in extracellular spaces. That way, intracellular infection is prevented.