The Immune System - GCSE Biology | kayscience.com

In this video, Pathogens cause disease. On the surface of pathogens are antigens. A white blood cell called a lymphocyte will bind the antigen on the pathogen and become activated. The activated lymphocyte produces antibodies. The antibodies bind to the antigens on the surface of the pathogen. The antibodies cause the pathogen to clump together and kills the pathogen.

To recap:
Antigens are found on the surface of pathogens.
Antibodies are produced by white blood cells called lymphocytes.
The antibodies produced by lymphocytes bind onto the antigens of the pathogen
The antibodies clump the pathogens together or kill them