HUMAN HEALTH - IMMUNITY 2

TYPES OF IMMUNITY

Based on the type of immune cell acting against the antigens, immunity can be classified into two types-

• Humoral immunity- mediated by antibodies produced by B-lymphocytes.

• Cell- mediated immunity- mediated by T- lymphocytes by directly attaching themselves to the antigens.

During organ transplantation, tissue matching and blood group matching are essential before undertaking any graft/transplant and even after this the patient has to take immuno suppressants all his/her life because the body is able to differentiate ‘self ’ and ‘nonself’ and the cell-mediated immune response is responsible for the graft rejection.

Based on the nature of antibodies, immunity is divided into two types-

• Active immunity- When a host is exposed to antigens ( living or dead microbes or other proteins) antibodies are produced in the host body.
• Natural active immunity- natural infection and antibody production.
• Artificial active immunity- through vaccination. Eg. Polio.
• Passive immunity- When ready-made antibodies are directly given to protect the body against foreign agents.
• Natural passive immunity - The yellowish fluid colostrum secreted by mother during the initial days of lactation has abundant antibodies (IgA) to protect the infant.
• Artificial passive immunity - antivenom on snake bite.

VACCINATION AND IMMUNIZATION

Vaccination is the process of introduction of vaccines into the body to produce antibodies against the antigens to neutralize the effect of pathogens during actual infection.

Vaccines are the dead or weakened pathogens introduced into the body.

The dead or weakened pathogen leads to the production of antibodies -- neutralize the same pathogen in later infection.

Immunization is the process where immunity is developed against a particular pathogen.

Using recombinant DNA technology antigenic polypeptides of pathogens in bacteria or yeast.

Example- hepatitis B vaccine produced from yeast.

ALLERGY

The exaggerated response of the immune system to certain antigens.

Aka hypersensitivity reaction.

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

Common examples of allergens are mites in dust, pollens, animal dander etc.

Allergy is due to the release of chemicals like histamine and serotonin from the mast cells.

The antibodies produced to these are of IgE type.

Symptoms of allergic reactions include sneezing, watery eyes, running nose and difficulty in breathing.

Diagnosis- by injecting or exposing the patient to very small doses of suspected allergens.

Drugs like anti-histamine, adrenalin and steroids quickly reduce the symptoms of allergy.

AUTO IMMUNITY

The immune system of body can is able to identify and differentiate between self and non self.

Due to genetic and other unknown reasons, the body attacks self-cell -- damage to the body.

Rheumatoid arthritis is an auto-immune disease