Biology Today — May 2017

• Cardiovascular diseases are those diseases that affect the blood vessels and heart, for e.g.,
  (i) Arteriosclerosis - Hardening and loss of elasticity of the arteries, causes high blood pressure.
  (ii) Atherosclerosis - Lumpy thickness develops on the inner walls of arteries that prevent dilation of arteries.
  (iii) Hypertension or high blood pressure - Arterial pressure exceeding 120/80 mmHg; can result in heart failure, kidney
  damage, etc.
  (iv) Myocardial infraction - Clot formation in the lumen of coronary artery, results in “heart attack”.


• Cerebrovascular accident (CVA) or stroke is the sudden interruption of blood flow to a portion of the brain due to a
  blockage or rupture of a cerebral blood vessel. Thus, the brain cells do not get sufficient oxygen and glucose. This can cause
  paralysis, loss of speech, etc.

IMMUNITY

• Immunity is the ability of the body to protect against all types of foreign bodies like bacteria, virus, toxic substances, etc., which
enter the body. It is also called disease resistance. The lack of immunity is known as susceptibility.
• The study of body’s defence mechanism against pathogens is called immunology.

• Edward Jenner (1749 - 1823) is known as the Father of Immunology.

• Antigens are substances which when introduced into the body, stimulate the production of antibodies.

Flow chart : Types of Immunity

Types of Immunity

Person’s own cells produce antibodies in

response to infection or vaccination; is

slow and takes time to form antibodies,

long lasting and harmless.

Develop when readymade antibodies

are directly injected into a person to

protect the body against foreign agents;

gives immediate relief; not long lasting.

(i)  Physical barriers - Skin, mucous membrane. Active immunity Passive immunity

(ii)     Physiological barriers - Bile, cerumen, urine,

nasal hair, etc.

(iii)    Cellular barriers - WBCs, natural killer cells,

PMNL-neutrophils, etc.

(iv)    Cytokine barriers - Interferons, interleukines.

Acquired/Adaptive/Specific defence mechanism. It is acquired after

birth during one’s lifetime. It is specific and mediated by antibodies that make

the antigen harmless. Unique features of acquired immunity are specificity,

diversity, discrimination between self and non-self and memory.

Innate/Inborn/Non-specific defence mechanism. It

is inherited since birth and consists of four types of barriers

against the entry of foreign agents into the body.

Components of Acquired Immunity

• It has two components:

1. Antibody mediated immune system (AMIS) or humoral immunity

• It consists of antibodies that circulate in the body fluids like blood plasma and lymph.

• B-lymphocytes or B-cells produce antibodies that regulate antibody
mediated or humoral immunity.

• T-lymphocytes do not secrete antibodies but help B lymphocytes to produce

them.

• B-cells give rise to:

• Plasma cells (Effector B-cells) : The antigen specific T-cells
  stimulate specific B-lymphocytes to multiply rapidly, forming clone of
  plasma cells.


• Memory B-cells : Some of the activated B cells do not differentiate
  into plasma cells but rather remain dormant as memory B-cells until
  activated once again by a renewed attack of the same antigen.

Antigen enters body

Flow chart:Functioning of Humoral Immunity

Other B-cells “remember”

the antigeni.e., memory cells

Some B-cells become

plasma cells

Plasma cells produce

antibodies

Antibody reacts

with antigen

Memory cells cause the

production of new plasma cells

when same antigen again

enters body.