The Sympathetic Nervous System, part of the Autonomic Nervous System, regulates the fuctioning of the Lymphoid organs, which are in charge of producing the main cells for the Immune System. When a person is stressed, it causes nervous tension in the body, and it affects the signals given by the Nervous System to the body. So when the Lymphoid organs receive a distorted signal from a stressed person, it affects the production and functioning of immune cells, making our Immune system innefective against common infections.
