Innate immunity or Non-specific defence mechanism

Our
body is equipped with bombs and machine guns to combat with intruders. But our
body has also fortress wall with highly sensitive alarms and are heavily
guarded.

Why
innate immunity is called non-specific defence mechanism?

This
defence strategy is same for most type of infections or pathogens, hence called
as non-specific defence mechanism. It protects body from infection primarily by
blocking pathogen entry or destroying pathogens that has entered, by different
means other than antibodies.

Innate
immunity is also known as inborn/familial/natural or genetic immunity.

Major
features of innate immunity

It
is inherited from parents and present from birth itself

It
offers immunity throughout life time

Prior
contact or interaction with pathogen or its antigen is not essential

t
protects the individual from getting diseases of other organisms

Innate
immunity involves removal of pathogens at two levels either externally or
internally

This Figure depicts major physical and
chemical barriers that blocks pathogen entry

Skin the largest organ in the body and is undoubtedly the major physical barrier that blocks pathogen entry. Apart from its role as an impenetrable barrier, it secretes various chemical weapons that avoid pathogen entry. The skin epidermis is approximately 10-30 cells thick, as thick as a page. The outer layer is the stratum corneum which are exposed and subjected to injury, and wear and tear. Such damaged cells of stratum corneum are continuously replaced by cells produced in the innermost layer of epidermis, stratum basale. The cells in the stratum basale pass through a middle layer,stratum spinosum where protein keratin is added which makes skin tough and water resistant. The new cells that reach stratum corneum remain for a month before they are shed and replaced by newer cells from stratum basale. In short,outer layer of skin, stratum corneum is a tough fully keratinised layer of dead cells capable of preventing pathogen entry efficiently.Contextual point: Why psoriasis?

Psoriasis
is a chronic skin disorder in which epidermal cells (cells at the stratum
corneum) are replaced every 3 to 4 days that is about eight timed faster than
normal.

Otherpotential routes of pathogen entry
are the openings in the body to the outside that is digestive tract,
respiratory tract and urogenital tract. Microbes are always at the
door step of these tracts for getting an entry. But our body has different
plans. Let us look in detail as points.

Mucus
secreted by mucous membrane that traps microbes and immobilise them

Microbes
inhaled are trapped by mucus secreted by cells lining the smaller bronchi and
bronchioles. In addition to this,cilia in all these passages help in sweeping
out entrapped microbes.

Somehow
if a pathogen enters body systems, then body uses defencemechanisms such as
vomiting, diarrhoea, coughing sneezing and mucous secretions to expel pathogen.

We
have discussed only the physical barriers of first line of defence. Now you may
thing, is it possible for a pathogen to enter human body?

Our defence
system is more sophisticated and complex than a nations defence system. It is
almost fool proof. But our enemies are also evolving side by side. The race is
on and let us discusses the internal defence of first line of defence in the
next post

Now
the microbe has breached the physical barrier, what will our defence system do?