What substance do lymph nodes produce that assist in immunity diseases?

Lymph nodes are a part of the lymphatic system, a component of the body's immune system.
There are several groups of lymph nodes, which are small, bean-shaped, soft nodules of tissue.
The ones most frequently enlarged or swollen are found in the neck, under the chin, in the armpits, and in the groin.

The main function of the lymphatic system is to produce, maintain and distribute lymphocytes.

Lymphocytes identify and attack damaged or infected cells in the blood.