Immunity
a) Types of immunity – innate and discussions.
hypersensitivity acquired.autoimmunity and b) Immunization schedule. immunizing agents Immunoprophylaxis (vaccines, sera etc.)
c) Hypersensitivity and autoimmunity.
d) Principles and uses of serology
tests
Types of immunity
Immunity :-
“Immunity is defined as the resistance of the body towards the harmful effects caused by the pathogenic organism and other toxic factors”
(Immunity is the resistance shown by the host against the condition caused by the micro organism and its products (toxin).)
Immunity
Immunity is defined as the ability of the body to recognize, destroy and eliminate antigenic material (bacteria, virus, proteins) foreign to its own.
(Immunity is the ability of the host to identify, destroy and remove antigenic material – bacteria, viruses, proteins – coming into the body from outside.
Protection against infectious disease is an effective result of immune response. It is a reaction against a completely foreign antigen.
Types of immunity
1) Innate immunity
Innate or native immunity is genetically (inherited) to a person, there is no effect of contact or immunization of the micro-organism. When it creates resistance against general infection, it is called non-specific and when it creates resistance (barrier) against a single pathogen, it is called specific. This type of immunity is found at species, racial and individual level.
(i) Species immunity
In species immunity, almost every member of a species has immunity against a pathogen. The mechanism of this immunity is not fully understood, but it is believed to be due to physiological and biochemical differences between different host species tissues.
Which determines the cultivation of the pathogen.
This was first observed in Pasteur’s experiment of anthrax on frogs, in which frogs were naturally resistant to the disease.
But when kept at 25 c to 35 c, some of them were found to be susceptible to anthrax.
(ii) Racial immunity (hereditary)
Different races in the same species have different susceptibility against the same type or generalized infection. This is known as racial immunity.
Immunity against anthrax in Algerian sheep is an example of this.
But nowadays it can be developed to some extent, in some parts of Africa people of plasmodium falciparum have resistance.
(iii) Individual immunity
In innate immunity, the difference found in different individuals of the same race is called individual immunity
Age, hormonal influence and nutrition are factors influencing individual immunity.
2) Acquired immunity
A person acquires resistance against micro-organism during his life is called Acquired immunity or Adaptive immunity. Thus it differs from innate immunity.
There are two types of acquired immunity.
(1) Active immunity
(2) Passive immunity
(ii) Passive immunity
Antibodies produced in one person are transferred (ready made) to another person to protect the person against disease, it is called passive immunity.
In other words, the body does not produce antibodies. But it depends on readymade antibodies. Passive immunity comes in the following ways.
Injection of antisera.eg. ATS (for protection against tetanus)
Injection of gamma-globulin.
Maternal Immunity – Antibodies placenta transfer from mother to fetus. Maternal antibodies protect the baby for a few months after birth. Like against diphtheria measles etc.
Local immunity
Besredka gave the concept of local immunity. (1919-24) Its importance can be for the treatment of localized infection.
Which is done at the entry site of the pathogen.
Systemic immunity can be created against Poliomyelitis virus through killed virus vaccine.
which acts against the virus in the blood stream. But since the virus enters. (the gut, mucosa) does not affect the growth of the virus there.
Live / oral vaccine is given for this.
Which creates local (intestinal) active immunity
Immunization with killed influenza vaccine induces a systemic antibody response.
But it is not useful for local infection of respiratory tract. For this, locally live virus vaccine or immunoglobulin is given through the nose.
Herd Immunity
It shows the overall immunity level of the community, it plays an important part in epidemic control.
When most of the individuals of a community are immunized against a pathogen, the immunity of the entire community against that pathogen is seen as satisfactory, while when the level of herd immunity is low, there are chances of an epidemic.
Irradiation of communicable disease is based on high level of herd immunity and not high level immunity.
Ex.polio
💪 Mechanism of innate immunity
Skin-barrier, high salt concentration in sweat, sebaceous secretion, and long chain fatty acid act as bacterial cidal (kill bacteria).
Respiratory tract :-Mucus, cough reflex act as defense mechanism
GI-tract :– saliva, and Acidic PH gastric juice
Conjuctiva :- Lysozyme present in tears bacteriocidal, flush wash micro-organism
Inflammation
Mast cell – Release histamine which causes Vasodiatation and hence increase in Capillary permeability.
Inflammation process (redness, swelling, heat, pain) is necessary to reach the immune cells to the infected tissue.
Fever is also caused due to the process against this microorganism.
Mechanism of active immunity
Humoral immunity :– which depends on the synthesis of plasma cell antibody. In which it produces specific antibody against specific antibody and modifies its activity.
Cell-mediated immunity :- It is produced by the sensitivity of T-lymphocytes, which is very useful for resistance to chronic bacterial infection.
A vaccine is a preparation of a disease agent or its toxin when it is injected into the body. Then helps to produce specific antibody, or stimulates it. Hence the vaccine induces active immunity.
Vaccines are made in different ways
(i) Live attenuated organism :- Ex. Polio, Measles, B.C.G vaccine
(ii) Killed organism:- ex.Cholera vibrio
(iii) Toxoid :- Ex.Diphtheria, Tetanus
(iv) Mixed/Combined :- Combination all types of vaccine.
IMMUNIZING AGENTS
Immunization :-
In this, vaccine is inoculated to bring individual artificial immunity
Immunizing agent :-Immunizing agent is divided into two parts. has been divided into two parts.
(1) Vaccine (antigen material)
(2) Immunoglobulin’s (antibody material)
For the prevention of disease, organisms are introduced from animals to humans, the principle of vaccination was discovered accidentally in 1776. English physician jenner observed that milking animals infected with cow pox were protected against the dreaded disease small pox. Jenner applied these principles to humans. The material taken from the eruption of cow pox was transferred to man, and that man was able to escape from small pox infection even during the epidemic of small pox.
Vaccine and vaccinations
A vaccine is a preparation of antigen when it is given. Then it stimulates the formation of specific antibody in the body.
Vaccine is made from live organism (attenuated). Either prepared from killed organism or toxoids or a combination of each. If more than one immunizing agent is in a vaccine, it is called mixed or combined vaccine.
Immunoglobulins (Gamma gobulins)
The term Immunoglobulin was first used in 1959 for serum protein. Immunoglobulins produced by the reticuloendothelia system of the body are very important for the study of immunity. Human Immunoglobulin system (human serum) is of five classes. IgG, IgA, Ig M, Ig D, Ig E They differ by their antigenicity and physical-chemical properties.
Immunoglobulin is very important containing 80% of serum antibody of normal human being. This only Immunoglobulin passes through the placenta and reaches the fetus and provides immunity to the fetus.
10% Antibodies are Immunoglobulin. It is found in body fluids like milk, saliva, tears, mucous secretion. Mucous surface of minute leakage prevents organisms from going into circulation, its synthesis starts after 2 weeks of birth.
Human serum contains 5 to 10% antibodies. Its large antibodies are called macroglobulin. It remains intra vascular and cannot pass through the placenta, its life is short. It has bacteria killing capacity.
Less than 1% (Total immunoglobulin) is present. Not having antibody activities.
The least amount of immunoglobulin in the body is found in serum at trace time. Responsible for immediate allergy and anaphylaxis.
HYPERSENSITIVITY
Immunity is seen as a protective process. But it is only a small part of the process for antigen response.
Sometimes the immune response can be injurious to the host. Which becomes responsible for tissue damage, diseases or even death.
Harmful effects arising from contact with specific antigen is called hypersensitivity.
Hypersensitivity is divided into two parts depending on the time of clinical response that develops in the host.
(1) Immediate hypersensitivity (B cell or antibody mediated)
(2) Delayed hypersensitivity (T cell mediated)
Type-1 Hypersensitivity
(Anaphylactic or regain dependents)
Antibodies are fixed on the surface of tissue cells (mast cells) and basophiles of sensitized person.
Pharmacological active substances combined with antigen cell with fixed antibodies are responsible for causing clinical reaction.
Type-2 Hypersensitivity
(Cytotoxic or cell stimulating)
This type of reaction begins with the reaction of antibodies against a cell or tissue or the binding of an antigen to a cell.
It causes cell damage in the presence of mononuclear cells. Type-II reaction is a reaction between hypersensitivity and autoimmunity.
Conjugation with antibodies in many cases works to stimulate the cell rather than damage it.
Long acting thyroid stimulator (LATS) is an example of this. Antibodies stimulate the thyroid cells and increase the secretion of thyroid hormones.
Type-3 Hypersensitivity
(Immune complex or toxic complex disease)
In this, damage is caused by antibody-antigen complexes.
Due to its precipitation around small vessels, it causes damage to the vessels or due to its infiltration in the membrane, the efficiency of the membrane decreases.
Damage to the walls or basement membranes of small blood vessels (membranes) causes inflammation.
Type-4 Hypersensitivity
(Delayed or cell mediated hypersensitivity)
Cell mediated immunity is a necessary reaction
Activated antigen of sensetized T4(TDH) Lymphocytes.
Due to which lymphokines are secreted.
Local infiltration of mononuclear cells is seen in this reaction.
AUTOIMMUNITY
Immune system is known as non self (foreign) antigen or self antigen.
But its response is also seen due to which the mechanism of the serum body or system deteriorates. Which is known as immunological reaction or auto immunity or auto immune disease. It is found in two types.