B_T_2015_02_

types of ImmunIty

• The different types of immunity are given in the

following flow chart:

Innate immunity/non-specific defence

mechanism

• Non-specific defence mechanism is similar for most

type of infections. It resists infection by blocking the

entry of pathogens into the body or by destroying the

microbes through means other than antibodies.

•    This type of immunity is inherited and provides

protection, since birth, and throughout life.

•    It is also known as innate/inborn/natural/familial/

genetic immunity.

•    It is further of two types : external and internal

defence.

external defence (first line of defence)

•    It comprises physical and chemical barriers to the entry

of pathogens into the body.

•    Physical barriers prevent the entry of pathogens into

the body, while chemical barriers are certain chemicals

secreted by the skin and by the mucous membranes,

which destroy the pathogens that enter into the

body.

•    The table given below shows the different physical

and chemical barriers.

Internal defence (second line of

defence)

•    It occurs when the first line of defence fails to prevent

access of pathogens to the tissues.

•    The body’s internal defence is carried out by the different

white blood corpuscles or leucocytes, macrophages,

natural killer cells (NK cells), inflammatory reactions,

fever, interferons and complement system.

•    The internal defence mechanisms operate in a

coordinated manner to prevent damage to the body

organ by pathogens.

Type Eyes Skin

Gastrointestinal

tract

Respiratory

tract

Urinogenital

tract

Physical

barriers

Tears by lacrimal

gland

Perspiration,

sloughing off of

skin

Flow of food, saliva,

mucus by mucous

membrane

Mucus by mucous

membrane, cilia,

nasal hair

Urine, mucus,

by mucous

membrane,

semen flow

Chemical

barriers

Lysozyme in

tears

Sebum (fatty

acids), lactic acid,

lysozyme, cerumen

Acidity, enzymes

(proteases), bile,

bicarbonate ions

Lysozyme in nasal

secretions

Acidity in vaginal

secretions,

spermine and zinc

in semen

Antimicrobial peptides (defensins)

Table : External defence mechanisms

 West Bengal JEE 18 th April and 19th April

 MGIMS Wardha 19 th April

 Kerala PMT 22 nd April and 23rd April

 AIPMT 3 rd May

 COMEDK 10 th May

 AIIMS 1 st June

 JIPMER 7 th June

Important Exam Dates 2015