How does the body respond to pathogens- Covid 19

 IMMUNOLOGY -PART 1 

DEFINITION OF IMMUNITY

Resistance exhibited by the host against any foreign antigen including microorganism

TYPES OF IMMUNITY:

A) INNATE IMMUNITY

B) COMBINED

C) MISCELLANEOUS

A) INNATE IMMUNITY

• It is the resistance possessed by birth,by virtue of genetic and constitutional make up .
• It does not depend on prior contact with foreign antigen.

TYPES:

SPECIES IMMUNITY

• Resistance to a pathogen
• Shown by all members of particular species
• Eg- Bacillus Anthracis infect human,chicken does not get affected.

RACIAL IMMUNITY

• Within 1 species,different resistance to infection

INDIVIDUAL IMMUNITY

• In same race and species there will definitely be difference in resistance to infection
• For example: imagine  you and our friend of same age group ,the resistance to infection might be at least slightly higher or even lower than your friend it depends on the individual .

FACTORS INFLUENCING INNATE IMMUNITY;

AGE:

• Foetus and old person they both high susceptibility to various infection as a foetus has a immune system that's still developing and immature ,where as old person will have gradual waning of immune response .

HORMONE:

• Hormonal disorder like diabetes mellitus ,hypothyroidism will enhance susceptibility to infection.

NUTRITION:

• Malnutrition predisposes to bacterial infection 
• In malnutrition : hormonal and cell mediated immunity plays a role 

C)MECHANISM OF INNATE IMMUNITY:

EPITHELIAL SURFACE:

SKIN:

• Act as mechanical barrier to microorganism
• Provide bactericidal secretion skin can be freed of transient flora,but not resident flora they prevent colonisation by pathogens .

RESPIRATORY TRACT:

• Inhaled particles get arrested in nasal passage on moist mucous membrane
• Mucous secretion of respiratory tract 
• Respiratory tract traps and propel towards pharynx it can either be swallowed or coughed out 
• Cough reflex plays a important role in defense mechanism 

INTESTINAL TRACT:

• SALIVA present in the mouth act as inhibitory effect on bacteria it may be swallowed or destroyed by acidic pH of gastric juice.

CONJUNCTIVA:

• TEARS that roll down when you feel sad or even when we are extremely happy they help in flushing away bacteria and dust.

GENITOURINARY TRACT:

• In females: vaginal secretion free many pathogen
• In males ; semen is believed to be antibacterial substance

ANTIBACTERIAL SUBSTANCE:

• In blood and tissue both specific antibacterial substance 
• Substance like: lysozyme,complement,betalysin

CELLULAR FACTORS:

• When a infective agent invade the epithelial surface ,tissue factor come into play for defense
• When pathogen agent invade tissue
• Exudative inflammatory reaction occur by ,accumulation of phagocyte at site of infection
• phagocytic cell ingest these organism and destroy them.

INFLAMMATION:

• Entry of pathogen leads to tissue injury /irritation 
• Non specific defense mechanism
• Lead to: 

1. Vasodilation,outpouring of plasma
2. Increased vascular permeability
3. Cellular infiltration 

FEVER

• Natural defense mechanism
• Destroy infecting organism
• Stimulate production of interferon

 ACQUIRED IMMUNITY

• Resistance acquired by individual during life is known as acquired immunity

Types of acquired immunity:

• A)Active
• B)Passive 

Active immunity mechanism 

Humoral immunity 

• Antibody mediated immunity
• Produce specific circulating antibody+antigen  modify their activity
• Different forms to modify their activity:

1. Lysis of antigen molecule
2. Toxin-neutralized 
3. Phagocytosis

CELL MEDIATED IMMUNITY :

• Depends on T-lymphocyte developed against certain antigen

Types: 

1. Natural active
2. Artificial active

NATURAL ACTIVE

• Long lasting
• For example person recovering from smallpox infection develop natural active immunity.

Artificial active

• Its produced by vaccination 
• Vaccine are prepared from live,attenuated,killed microorganism

Vaccine:

A) Live vaccine:

• BCG  for tuberculosis
• MMR vaccine for measles,mump,rubella

B) Killed vaccine:

• Hepatitis b

C) Bacterial product 

Diphtheria toxoid for diphtheria

B) PASSIVE IMMUNITY:

• Induced by preformed antibodies (antiserum) against infective agent
• Protection starts immediately
• No latent period
• Short lasting 

i) Natural:

• Mother to foetus 
• Maternal antibodies through transplacental route
• Milk ( colostrum) rich in Ig E antibodies

ii) ARTIFICIAL :

• Achieved through parenteral administration of antibodies.

USES OF PASSIVE IMMUNITY;

• Immediate short term protection
• Treatment of serious infection

MISCELLANEOUS:

COMBINED IMMUNISATION:

• Combination of active and passive immunisation

ADOPTIVE IMMUNITY

• Injection of immunologically competent lymphocyte

Transfer factor:

• Instead pf whole lymphocyte,extract of immunologically competent lymphocyte

LOCAL IMMUNITY:

• At site of entry : gut mucosa,nasal mucosa
• Natural infection/live viral vaccine is administered orally ,intranasally to provide local immunity

HERD IMMUNITY:

• Overall resistance in the community
• When ,herd immunity decreases the chance of epidemic increases
• Eradication of any communicable disease depend on development of high level of herd immunity in individual.

AIM OF THIS POST:

Vanakam, today we started of from the definition of immunity then moved on to in detail types and mechanism of immunity .I felt this post would help people understand what happens to our body when we get arrested by pathogens which is need of the hour .Yes,we all know Covid -19 is spreading much more faster than the first wave  one of the main reasons would be herd immunity ,communicable disease such as coronavirus ,tuberculosis the major disadvantage being that together we all need to develop more resistance to such pathogens one option is definitely  maintaining hygiene ,oral health status ,rich diet;vitamin c  apart from these we have a option to get vaccinated ,now let's not get into debate of is it hazardous and all as far the current situation is I would recommend all of you to refer with your family doctor ,check your immune status then get vaccinated if you have a chance.

GENERAL TALK:

Here at stencildent we are celebrating this week as #classificationweek so yesterday day 1 - we learnt about classification of composite if you haven't checked it out yet then do click on this to learn more classification of composite today being day-2 we have discussed about types of immunity the topic was been suggested by Nandhini are very own stencildent subscriber ,If you would also like to suggest topic do get contacted with us in instagram as well as we will be posting notification of all post ,that would be really helpful . If you like this post do let me know in the comment section below 

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