Immunity is the bodys ability to resist or fight off infection and dieases by recognizing and eliminating harmful pathogens like bacteria, viruses, and fungi.
Types of Immunity –
Immunity
classified into two types
1. Innate immunity (non specific , natural )
2.
Acquired immunity (adaptive , specific)
1. INNATE IMMUNITY :-
Inborn
immunity
1
non specific immunity or natural immunity .
2 it also called nonspecific or natural
immunity.
3 it is present from birth .
4.it is inherited from mother to offspring through placenta.
5.innate immunity is in born capacity of the body to resist the pathogen
6. it
does not depend on previous exposure to foreign particles it is is called as non specific immunity.
Innate
immunity comprises the various types of barriers .
which prevent entry of
foreign agent into the
body –
Innate immunity various types of
barriers
a] Epithelial surface -
these barriers prevent
entry of the microorganism into the body
it consist
of surface barrier and internal defence
system or first and mucous membrane.
1)skin
; skin
prevent entry of bacteria , virus or other pathogen oil and sweat make the
surface acidic so growth of microb prevent.
2.Mucous membrane :-
it
secreat mucus an it coting of epithelial lining of the respiratory ,
gastrointestinal and urinogenital tracts it help remove microorganism entering
the body .
3.Body secretion
: sweat
oil, lysosome, Hcl , digestive secretion
Gastric juice {HCL} in stomach, lyosome contain saliva prevent growth of many
invading pathogen micro organisms ,
glycoprotein and inter form which
stop replication of virus and give protection against viral
infection interferon act as signaling
inside cells.
b)Antimicrobial substances in blood and
tissues:
1. The complement system contains more than 30 serum
proteins, circulating in the blood in an inactive state.
2. The presence of microbial pathogens activates the
'Complement cascade' to eliminate pathogens.
3.The cells infected with viruses and certain white
blood cells releases interferons are
a class of cytokines (soluble proteins) to stimulate other cells to protect
themselves from viral infection.
c) Cellular factors in innate immunity:
Natural defence against the invasion of blood and tissues by microorganisms and other foreign particles, is mediated to a large extent by phagocytic cells which ingest and destroy them.
Phagocytic cells (discovered by Metchnikoff in 1882)
are grouped as rnierophages and macrophages.
They remove foreign particles that enter the body.A
class of lymphocytes called Natural
killer (NK) cells is importa t in nonspecific defence against viral
infections and tumors.
d]
fever-
physiological barrier :-physiological
barrier like body temperature ,
pH various secretion prevent growth of many invading
pathogenic microorganism
it is bacterolytic enzyme it present in tear.
Body temperature :- leucocytes release pyrogens which cause rise in
body the temperature inhibits the growth
of many pathogens..
e] Acute phase proteins [ APPs] –
infection on injury leads to a sudden increase in concentration of certain plasma , proteins collectively called acute phase protein.
These include C relative protein [ CRP] Manose
binding protein Alpha-1 acid
glycoprotein, serum Amyloid p,
Apps are belived to
enhance host resistance prevent tissue injury and promote repaire of
inflammatory lession
Inflammatory barriers :- inflammation
is non specific defensive response of
the body to tissue damage an infection and tissue
injury causes redness
welling pain and the localized manifestation is clled inflammatory response response is due to release of certain
chemical like histamines
and prostsglandin it released by damaged mast cell of connective tissue and basophils of blood
which dilate the blood vessels.leucocytes release pyrogens .
which cause rise in
temperature which stimulate phagocytes and inhibitsgrowth of microorganisms.
II. Acquired immunity :
Adaptive
immunity/ specific immunity –
Resistance or
immunity an individual acquires during life is called acquired immunity
Ability of the body to defend it self against
specific invading non self foreign agent , like bacteria, viruses toxin and
transplanted tissue is called specific resistance or immunity
Aquired immunity is found only in vertebrates , It
supplement the protection provided by innate immunity , it requires several
days to become activate
Unique feture of acquired immunity-
a)
Specificity-
ability to different various foreign particals, it
is specific for each type pathogen
b)Diversity
–
it can recognize a more purity of divers pathogen o
r foreign molecule
c)
Discrimination between self and non self
–
capacity to
differ into own body cell and foreign or molecule self to non self
d)
Memory-
after first encounter specific pathogen retain the
memory of encounter second time of encounter of same pathogen bring quick and
strong immune respons
TYPES OF ACQUIRED IMMUNITY -:
[specific or acquired immunity ] maybe
2type
1. active immunity or
2. passive immunity
I. ACTIVE IMMUNITY :
a. The resistance or immunity developed by an
individuals own cells in response to an infection or a vaccine.
b. It has no side effect .
c. It provide relief only after long period.
d. it is long lasting ,
It is two type ---
A. Natural acquired active
immunity:
Immunity acquired due to infection is called natural
acquired immunity
It devloped by antibodies produced by an
individual own cell
It is developed after entery of pathogen in
the body ex. Measles
B. Artificial acquired active immunity _
Immunity is acquired
artificially by vaccination ,vaccine contain dead or live by attennated
pathogen or toxic
secreated by pathogen By taking vaccine injection antibody, secretion is
stimulating for body defence ex. polio, BCG vaccine etc.
II-PASSIVE IMMUNITY
The resistance that is
transmit to an recipient in a readymade form is called passive immunity
They give immediate
protection ,passive immunity can be acquired either naturally or artificial it cause of side
effect.
Acquired passive immunity is of two types :-
1.Natural Acquired Passive
immunity-
This is involves transfer
for antibodies from mother to her unborn child through placenta
IgG from placenta during the later part of her
pregncy.
This provide protection to the baby until, its own immune system.is fully function passive
immunity provide through colostrums it is an first secretion of the mammory
gland along with mother milk IGAtthrough milk
.
2.Artificial acquired passive immunity:-
This immunity have been
formed in one individual and are extracted and then injected in to the blood of
another individual. immunity developed previousaly prepaired anti bodies and
injection to another individuals, ex.
specific antibodies combating tetanus and diphtheria used to culture in horses
or cows and innjeted in human vaccine for cholera,typhoid,and hepatitis have
been prepaired genetic enginiarings.
B. Cells of Immune System:
There are two main types of cells involved in the
working of Immune system. They are
(a)
Lymphocytes
(b)
Antigen Presenting cells.
a. Lymphocytes:
i. Lymphocytes are the main cells of the immune
system.
ii. They, like the other blood corpuscles, arise
from the stem cells, the haemocytoblasts, present in liver of the foetus and in
the bone marrow in adult.
iii. Some of them undergo differentiation in the gut
- associated bursal lymphoid tissues (Tonsils, Peyer's patches) and are called Bursal or B-Iymphocytes;
iv. others are differentiated in the thymus gland
and are termed as T -lymphocytes.
v. The mature lymphocytes pass into body fluids
(blood and lymph) and circulate in the body.
vi. Many ofthem stay in the lymph nodes. The
B-Iymphocytes and T-Iymphocytes form humoral or antibodymediated immune system
(AMIS) and cell-mediated immune system (CMIS) respectively.
vii. Both the immune systems need antigens to come
into action, but they respond in different ways.
Mechanism of response of T -lymphocytes
to antigens:
On coming in contact with an antigen, T -lymphocyte
forms clones 0 ']I-cells which are similar but they perform different
functions.
The clone has four types of T-lymphocytes:
-
i. Helper T -cells: Sensitized
helper T -cells produce lymphokines for performing several types of functions
like proliferation of other T -cells, stimulation of B-Iymphocytes,
macrophages, etc.
ii.
Killer T -cells or Cytotoxic T -cells:
They
directly attack and destroy invading microbes, infected body cells and cancer
cells. Killer T -cells bind to infected cell and sec ete perforins. Then
perforins form a hole in infected cell. It also releases substances that kill
the cell, hens the name cytotoxic T-cell.
iii. Suppressor T -cells:
These
cells suppress entire i mune system against attack on the own body cells.
iv, Memory
T -cells: These are previously
sensitize cells which retain the sensitization memory for long time in the future.
Mechanism of action of B-Iymphocytes to
antige s:
i. B -lymphocytes are sensitized directly; 15 oth
antigens as well as by helper T -cells.
ii. Activated B-Iymphocyte multiplie veryfast to
produce clone of plasma cells and memory B-cells.
iii. The plasma cells produce specia . zed
glycoproteins, called antibodies which are circulated through body fluids
(humor) like blood and ymph.
iv.The antibody molecules may bind to a cell
membrane or they remain free.
The free antibodies have three main functions:
i.
Agglutination
of particulate matter,
including bacteria and viruses. The immobilized mass is then engu eo by
phagocytes.
ii.
Opsonisation
or coating of bacteria
to facilitate their subsequent phagocytosis by macrophages.
iii. Neutralization
of toxins released by
bacteria e.g. tetanus toxin.
Each
antibody is specific for a particular antigen.
Antigen Presenting cells:
i. Antigen presenting cells engulf invading
pathogens and process the antigens.
ii.Then the processed antigens are presented on
their own surface.
iii.These cells are able to deliver a stimulatory
signal that is necessary for activation of helper T-cell.
C. Vaccination:
Administration of vaccine (i.e. inactivated pathogen
or antigenic protection of particular pathogen) to protect against a particular
pathogen, is called vaccination.
The body's immune system helps to protect against
pathogens that cause infection.
It's an efficient system, most of the time, it
either keeps microorganisms out or tracks them down and gets rid of them.
some pathogens destroy the immune system. it can
cause serious illness.
Vaccination is a way to "teach" the immune
system as to how to recognize and eliminate pathogenic organism. That way, body
is always prepared if you are ever exposed.
Vaccination is an important form of primary
prevention, that can protect people from getting sick.
Vaccination has allowed us to control diseases like
measles, polio, tetanus and whooping cough that once threatened many lives.
It's important that as many people as possible get
vaccinated.
It also helps to protect the society.
Vaccinations are safe:
Vaccines are considered to be safe.
They are rigorously tested and go through many
rounds of study, examination, and research before they are used for the general
public.
Extensive research and evidence show that vaccines
are safe their side effects are rare and typically mild
Structure of Antibody:
Antibodies are glycoproteins which are highly
specific to specific antigens.
They are also known as Immunoglobulins (Igs),
produced in response to antigenic stimulation.
Antibodies are produced by plasma cells which in tum
are formed by B-lymphocytes.
The mature plasma cells produce antibodies at an extremely rapid rate i.e. about 2000 molecules per second.