1. HUMAN HEALTH & DISEASES L05
Active and Passive Immunity
Active Immunity Passive Immunity
It is developed due to contact with pathogen
or its antigen.
It is developed when readymade antibodies
are injected into the body.
It has no side effects or only few. It may cause reaction.
It is long lasting. It is short lived only for few days.
It takes time to develop active immunity. It is used when the immune response has to
be faster.
Vaccination & Immunization
Vaccination is the process of introduction of vaccine (weakened or inactivated pathogens)
into a person to provide protection against a disease.
Immunization is the process by which the body produces antibodies against the vaccine.
Vaccination provides immunity after a time gap.
The principle of vaccination and immunization is based on the property called “memory”
of the immune system.
The vaccine generates memory B and T-cells, that recognize the pathogen on subsequent
exposure and produce antibody.
If a quick immune response is needed as in tetanus infection, performed antibodies or
antitoxin is injected into the patient. This type of immunization is called passive
immunization.
Hepatitis-B vaccine has been produced from yeast by recombinant DNA (rDNA)
technology and acts against Hepatitis-B virus which causes Jaundice and liver cancer.
Allergies
The exaggerated or hypersensitive reaction of the immune system to certain antigens
present in the environment is called allergy.
The substances/agents which produce an immune response in an individual is called
allergens. Eg. Pollen grains, animal dander, dust, feathers, drugs such as penicillin etc.
IgE antibodies are produced in response to allergens.
Symptoms: i. sneezing, ii. Watery eyes, iii. Running nose, iv. Difficulty in breathing.
Chemicals such as histamines and serotonin are released from the mast cells to cause
allergy.
Drugs: antihistamines, adrenaline, steroids.
2. Auto Immunity
It is an abnormal immune response in which the immune system of the body starts
rejecting its own body cells or “self” cells.
Eg. Rheumatoid arthritis, Addisson’s disease, Hoshimoto disease.
Immune System
The immune system includes lymphoid organs which acts as the sites of formation and
maturation of lymphocytes.
It plays a role in allergic reactions, auto immune disorder, and organ transplantations.
There are two types of lymphoid organs: a. primary and b. secondary.
Primary lymphoid organs
Those organs where origin/ maturation/ proliferation of lymphocytes occur.
Eg. Bone marrow and thymus.
i. Bone marrow:
It is the main lymphoid organ where all blood cells including
lymphocytes are formed.
Bone marrow provides the micro-environment for the
development and maturation of the B-lymphocytes.
ii. Thymus:
Thymus is a lobed organ located near the heart and beneath the
breastbone.
It becomes smaller with age.
It provides the microenvironment for the development and
maturation of the T-lymphocytes.
Secondary lymphoid organs
Those organs where lymphocytes interact with the antigen and proliferate to
become effector cells, eg., spleen, lymph nodes, tonsils, Peyer’s patches of small
intestine and appendix are called as secondary lymphoid organs.
i. Spleen:
It’s a large bean shaped organ and contains lymphocytes and
phagocytes.
It acts as a filter of the blood by trapping blood borne
microorganisms.
It has a large reservoir of erythrocytes. (graveyard of RBCs)
3. ii. Lymph nodes:
It is small solid structures present at different points along the
lymphatic system.
It traps the microorganisms or other antigens that have entered the
lymph.
Antigens trapped in the lymph nodes are responsible for the
activation of lymphocytes and produces immune response.
iii. Mucosa Associated Lymphoid Tissue (MALT)
It is formed from masses of lymphoid tissues present in the mucosa
of the respiratory, digestive, and urogenital tracts.
50% of the lymphoid tissue in human body is formed of MALT.
MCQs
1. Which of the following glands is large sized at birth but reduces in size with ageing?
a. Pineal gland
b. Pituitary gland
c. Thymus gland
d. Thyroid gland
2. An animal is said to have acquired active immunity when
a. He responds actively to a vaccine
b. He acquires immunity upon recovering from a disease.
c. It produces its own antibody in its defense
d. All the above
3. Lysozyme is an important antimicrobial secretion present in
a. Tears
b. Saliva
c. Nasal mucosa
d. All of these
4. White blood cells that do not show phagocytic activity are
a. Lymphocytes
b. Monocytes
c. PMNL
d. All of these
5. Antigens may be
a. Proteins
b. Complex lipids
c. Polysaccharides
d. All of these
