Immune System


The components of natural immunity are dendritic cells, macrophages, natural killer- cell and the complement system.

Dendritic cells – antigen-presenting cells for CD4 +T-helper lymphocyte crucial step in initiation of the immune response. In the elderly, dendritic cells become less.

Macrophages – specialize in phagocytosis and intra-cellular killing of microorganisms. Bacteria trigger macrophages to produce numerous chemicals and cytokines and promote the activation of T-helper lymphocytes. In the elderly, the rate of antigen clearance by macrophages decreases and the toxicity against tumour cells is low.

Natural killers (NK) cells – it can kill target cells spontaneously and are involved in host resistance to various tumour and infectious disease. With age, natural killer- cell activity remains unchanged or increased.

Complement – consists of interacting plasma protein, it is the main soluble effector of natural immunity .Healthy elderly persons appear to have slightly lower levels of complement component than do younger persons. Complement levels increase dramatically in younger persons with a bacteraemia but do not significantly do so in elderly persons.

Symptoms and Signs

Clinical effects of immune senescence (dysfunction):

  • Infectious disease :  reactivation of infectious disease is clearly established. Example: herpes zoster, the incidence increases five fold between the ages of 45 and 85. Associated with an age-related loss of cellular immunity to the varicellar-zoster virus.
  • Response to immunisation: production of specific antibody is decreased when vaccine containing antigen are given to elderly.
  • Cancer: immune senescence may impair the recognition and elimination of tumour cell. Example chronic lymphocytic leukaemia (CLL).
  • Degenerative disease of aging : related to immune dysfunction. Auto- antibody production tends to increase in the presence of chronic disease. Example: hypothyroidism, diabetes and hypopituitarism.


Age-related decreases in specific antibody production may account for the high incidence of mortality associated with pneumonia, influenza, infectireous endocarditis and tetanus among elderly.

Treatment/ Prevention

  • Get plenty of exercise. Exercise helps to boost the immune system.
  • Eat healthy foods. Good nutrition keeps the immune system strong.
  • Do not smoke. Smoking weakens the immune system. Avoid or limit alcohol intake.
  • Look into safety measures to prevent falls and injuries. A weak immune system can slow healing from falls and injuries.
  • To see doctor early if not feeling well.
  • To get specific vaccine immunisation as suggested by  the flu and pneumonia vaccines or  any other vaccines recommended by  health care provider.
Last Review : 28 August 2020
Writer : Dr. Sanidah binti Md. Ali
Reviewer : Dr. Ho Bee Kiau