Lymphocytes also cause tissue-rejection during organ transplants. The effectiveness of vaccines is based on this memory function of lymphocytes. These plasma cells secrete vast quantities of immunoglobins or antibodies that are tailor-made to attack the specific antigens of the particular bacteria, leading to its destruction. T-cells , which are derived from white cells that the thymus gland transformed to perform a specialized function. T-cells secrete more than fifty different types of powerful chemical substances called lymphokines that contribute significantly to the functioning of the immune system.
Lymphokines promote cell growth, facilitate cell activation, destroy cancer cells, etc.
In the average body, there are approximately one trillion lymphocytes, which constitute 20 percent to 40 percent of all the white blood cells. The entire lymphatic system flows toward the heart. Below the neck, the thoracic duct and the right lymphatic duct drain into subclavian veins that form the inferior vena cava which flows into the superior vena cava and directly into the heart. Thus, the lymph fluids reenter the circulation systems and are distributed throughout the body. Lymphomas can be cured with early diagnosis and treatment.