Biology Human Health and Disease Class 12 Part 4

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

Humoral immunity- the immunity which is mediated by antibodies produced by B-lymphocytes is called humoral immunity.

Cell-mediated immunity- The immunity which is mediated by T-lymphocytes by directly attaching themselves to the antigens is called cell mediated immunity.

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-suppresants 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, which may be in the form of living or dead microbes or other proteins, antibodies are produced in the host body, this type of immunity is called active immunity.

Example- antibody produced when any microorganism enters the body.•

• Passive immunity- When ready-made antibodies are directly given to protect the body against foreign agents this type of immunity is called passive immunity.

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 which neutralizes the pathogenic pathogenic agents during actual infection with the same pathogen.
➤ Immunization is the process where performed antibodies against the toxin are introduced into the body.
Example- performed antibody injection against snake venom.
➤ 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 present in the environment is called allergy.
• The nsubstances 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 s of allergic reactions include sneezing, watery eyes, running nose and difficulty, in breathing.
• The patient is diagnosed by injecting or exposing the patient to very small doses of allergens.
• Drugs like anti-histamine, adrenalin and steroids quickly reduce the symptoms of allergy

What is an autoimmune disease?

An autoimmune disease is a condition in which your immune system mistakenly attacks your body.

Due to genetic and other unknown reasons, the body attacks self-cell which results in damage to the body and is called auto- immune disease.

The immune system normally guards against germs like bacteria and viruses. When it senses these foreign invaders, it sends out an army of fighter cells to attack them.

Normally, the immune system can tell the difference between foreign cells and your own cells.

In an autoimmune disease, the immune system mistakes part of your body – like your joints or skin – as foreign. It releases proteins called autoantibodies that attack healthy cells. as foreign. It releases

Rheumatoid arthritis (RA)

In rheumatoid arthritis (RA), the immune system attacks the joints.

This attack causes redness, warmth, soreness, and stiffness in the joints.