It is the immune system which fights infections, and it does this by triggering defenses against invading bacteria. The antibodies and antitoxins of this system recognize these foreign bodies and send white blood cells to attack them. With his immune system weakened, a person is less able to withstand Epstein Barr virus, candidiasis, food allergies, arthritis, multiple sclerosis, cancer, etc.
Infections occur more easily.
The person is more susceptible to colds, infections, and viruses. Autoimmune disorders can result from conditions ranging from rheumatoid arthritis to kidney disease. Unrelenting stress, chronic allergies, chronic infections can exhaust the immune system. Other causes of a weakened immune system are vaccinations and immunizations against common childhood and epidemic diseases. The thymus gland seems to be the most affected by this weakening.