ALLERGY:

• Allergy is the exaggerated response of the immune system tocertain antigens present in the environment

• The substances to which such an immune response is produced are called allergens.

• Common examples of allergens à dust mites, pollens, animal dander, etc

• The antibodies produced to these are of IgE type.

• Reason of allergy is release of histamine and serotonin from mast cells.

• The use of drugs like anti-histamine, adrenalin and steroids quickly reducethe symptoms of allergy.

• Symptoms of allergic reactions include sneezing, watery eyes, runningnose and difficulty in breathing.

WHY ALLERGY CASES INCREASED?

Modern-day life style has resulted inlowering of immunity. It is due to protected environment in early days of life.

AUTOIMMUNITY:

• In memory-based acquired immunity, when the immune system does not differentiate between self-cells and foreign cells and also attack on selfcells and damage the body. This is called auto immunity disease.

• This is due to genetic and other unknown reasons.

• Example of autoimmune disease is Rheumatoid arthritis.

IMMUNE SYSTEM IN THE BODY

.• The human immune system consists of lymphoid organs, tissues, cells andsoluble molecules like antibodies.

Lymphoid organs: These are the organs where origin and/or maturation and proliferation of lymphocytes occur.

 • Immature lymphocytes differentiate into antigen-sensitive lymphocytes in PRIMARY LYMPHOID ORGAN.
 • Thymus and bone marrow are primary lymphoid organ
 • Organs like spleen, lymph nodes, tonsils, Peyer’s patches of small intestine and appendix are the SECONDARY LYMPHOID ORGANS.

 • The secondary lymphoid organs provide the sites for interaction of lymphocytes with the antigen, which then proliferate to become effector cells.

All the blood cells including lymphocytes are produce in bone marrow.
The thymus is a lobed organ located near the heart and beneath the breastbone.

The thymus is quite large at the time of birth but keeps reducing in size with age and by the time puberty is attained it reduces to a very small size.

Both bone-marrow and thymus provide micro-environments for the  development and maturation of T-lymphocytes. 

THE SPLEEN

• Large bean shaped organ.

• mainly contains lymphocytes and phagocytes.

• acts AS A FILTER OF THE BLOOD by trapping blood-borne microorganisms.

• also has a large reservoir of erythrocytes.

The lymph nodes are small solid structures located at different points along the lymphatic system. .Lymph nodes serve to trap the micro-organisms or other antigens, which happen to get into the lymph and tissue fluid. Antigens trapped in the lymph nodes are responsible for the activation of lymphocytes present there and cause the immune response.

MALT: Mucosa associated lymphoid tissue.

• They are located within the lining of the major tracts (respiratory, digestive and urogenital tracts) • It constitutes about 50 per cent of the lymphoid tissue in human bodySciencegajab.com