Immunity and Immune System

Immunity

The ability of a host to resist a particular infection or toxins by the action of specific antibodies or sensitized white blood cells produced by them in response to natural exposure of the organism is called as immunity.

Immune System

A complex network of specialized cells, tissues, and organs that recognize and defend body from foreign substances. Primarily disease causing microorganism such as bacteria viruses, parasites and fungi.

Lymphoid Organs:

·           PRIMARY LYMPHOID ORGANS – Thymus, Bone Marrow

·           SECONDARY LYMPHOID ORGANS – Lymph Node, Spleen

These organs produce immune cells or T-cells, B-cells, NK cells, macrophages, leukocytes that help to fight against pathogens

Factors Influencing the Immune Status of Individual Inherent

Species immunity

Species immunity is that in which a disease affecting one species does not affect the other species (Ex) Human do not contract cattle plague, chicken cholera, while animals are not affected by enteric fever.

Racial immunity:- is that in which various races show marked differences, in their resistance to certain infectious disease.

(Ex) Black Africans affected by a sickle cell anemia (a genetic disease) are resistant to Malaria while Malaria affects other human races.

Individual immunity:-The same racial background and opportunity for exposure some individual of the race experience severe infection. (Ex) Children are more susceptible to disease such as measles, chicken pox while aged individuals are susceptible to pneumonia.

Specific antibodies or sensitized white blood cells produced by them in response to natural exposure of the organism is called as immunity.

Types of immunity:- 3 types of immunity is in human.

1.        Innate immunity (natural or non specific)

2.        Acquired (specific or adaptive) immunity

3.        Active and passive immunity.

Innate (natural or Non-specific immunity:-

It refers to the inborn ability of the body to resist and is genetically transmitted from one generation to the next. The immunity offers resistance to any microorganism or foreign material encountered by the host.

Natural immunity results after acquiring certain disease Ex. Measles. This immunity lasts a life time.

Innate immunity can be divided in to species, racial, individual immunity

Acquired immunity (Specific or Adaptive):

Acquired immunity refers to an immunity that is developed by the host in its body after exposure to a suitable antigen or after transfer of antibodies.

Immunity can be described as either active or passive, depending on how it is acquired.

Active immunity: - Active immunity involves the production of antibodies by the body itself and the subsequent development of memory cells.

Passive immunity: - Results from the acquisition of antibodies from another source and hence memory cells are not developed.

Active immunity will result in long-term immunity but passive immunity will not due to the presence or absence of memory cells.

Both active and passive immunity can be induced by either natural or artificial mechanism.

Examples of active immunity: -

Natural – Producing antibodies in response to exposure to a pathogen if infection acquires. (e.g. Chicken Pox, Measles).

Artificial – Producing antibodies in response to the controlled exposure to an attenuated pathogen (e.g. vaccination)

Examples of passive immunity: -

Natural: Receiving antibodies from another host. (e.g. IgG - mother to feters via the placenta; IgA - From mother to new born via breast milk (colostrum)).

Artificial: - Receiving manufactured antibodies via external delivery (Blood transfusion of monoclonal antibodies).

Types of Immunity:-

Example

Types of immunization:-

Active immunization: is the induction of immunity after exposure of an antigen. Antibodies are created by the recipient and may be stored permanently. Artificial active immunization is where the microbe is injected into the person before they are able to take it in naturally.

Passive immunization: - It can be provided when people cannot synthesize antibodies, and when they have been exposed to a particular organ that they do not develop immunity.

Vaccine:-

Definition:

A vaccine is a biological preparation that provides active acquired immunity to a particular disease. A vaccine typically contains an agent that resembles a disease causing microorganism and is often made from weakened or killed forms of the microbe, its toxin or one of its surface protein.

The agent stimulates the body’s immune and that it may encounter in the future.

The term vaccine and vaccination were derived from variola vaccine (smallpox of the cow) This term was first discovered by Edward Jenner in 1796.

Types of vaccines:

·           Live Attenuated Vaccine

·           Inactivated Vaccine

·           Subunit Vaccine

·           Toxoid Vaccine

·           Conjugate Vaccine

·           DNA Vaccine

·           Recombinant Vector Vaccine

Live attenuated vaccine:

Live microorganism modified to be less deadly or closely related microorganism that induce immune response. The organism can be attenuated by growing it in prolonged culture. Attenuation means the loss of virulence of the pathogen.

e.g. OPV, MMR (mumps, measles, Rubella) BCG, varicella vaccine, yellow fever.

Inactivated vaccine or killed vaccine:

Whole microorganism destroyed by heat, chemicals, radiation, antibiotics.

e.g. Hepatitis A vaccine, Hepatitis B, Pneumococcal polysaccharide, IPV, influenza, Hib, Typhoid.

Toxoid vaccine:

Inactivated toxic compounds is toxoid. [toxins can be inactivated by using formalin]

Toxin +formalin ____________ toxoid

e.g. DPT, Antivenom, TT (tetanus toxoid)

Subunit vaccine:

A Protein component of the microorganism.

e.g. Surface Protein or Synthetic virus like particles lacking viral genetic material [unable to replicate] e.g. Hepatitis –B

Monovalent Vaccine:

Immunize against single strain of microorganism.

Multivalent Vaccine:

Immunize against multiple antigens strains or micro organism

The children with malnutrition have low resistance to fight against infection. Therefore children need timely immunization. All children have a rights to get vaccines, protection against preventable disease. Extremely malnourished children may show severe reaction to certain vaccines because they have low antibodies. e.g. Measles Vaccine.

Advantages of live/killed Vaccine:

Live Vaccine:

Killed Vaccine:

Maintaining a cold chain:

It is essential to maintain the favorable temperature with cold storage, to maintain the potency of vaccines. The temperature should be around 2°C to 8°C. The vaccine should be kept under freezing compartment. The thermometer should be placed in cold place to confirm the validity.

During transportation, the vaccines should be placed in a container maintaining the cited temperature or in a plastic bag in the ice box.

The Vaccines should be arranged according to their expiry dates for the better use.

Contraindications for the immunization:

An acute illness with fever.

When the child is on immune suppressive drug or on radiation.

A child suffering from leukemia, lymphoma, malignancy.

Infection & Its transmission:

1.        Entry of infection into human body:

·           Microorganism may enter the body in

·           one of the below three ways.

·           Digestive tract – Swallowed in contaminated food or water.

·           Respiratory tract – air contain pathogens

·           Skin and mucous membrane – through a wound, weekend surface or injections

2.        Organism leave the body of an infected person:

·           Excreta – Feces and urine.

·           Coughing and sneezing and sputum Pus and wound discharges

·           Blood (Mosquito bite and injection needles)

3.        Routes of transmission:

·           Fecal to oral route. Feces to Skin.

·           Droplet infection

4.        Prevention of infection:

·           Hand washing before preparing or eating food.

·           Eating only clean food, kept free from flies.

·           Handwashing after defecation.

·           Drinking boiled water. Avoid crowded places.

·           Immunization specially to protect children.

·           Cover the mouth and nose when coughing.