Biology Today — May 2017

VACCINATION AND IMMUNISATION

• Vaccine (L. vacca = cow) is a preparation/suspension or extract of dead/attenuated (weakened) germs of a disease which on
inoculation (injection) into a healthy person provides temporary/permanent active/passive immunity by inducing antibodies formation.

• The process of introducing a vaccine into an individual to provide protection against a disease is called vaccination.

Flow chart : Types of Vaccines

Types of Vaccines

First generation

vaccines

Live attenuated

vaccines

Prepared from

(weakened)

strains devoid of

pathogenicity e.g.,

measles, rubella,

yellow fever.

Inactivated vaccines

Dead or non-

replicating form of

pathogen, requires

higher doses or

boosters, e.g.,

influenza, cholera,

polio.

Subunit vaccines

Isolated antigens

that best stimulate

the immune system,

e.g., Hepatitis-B,

influenza.

Toxoid vaccines

Isolated deactivated

toxins (toxoids) used

to induce immune

response, e.g.,

tetanus, diphtheria.

Conjugate vaccines

Type of subunit vaccine, antigen

combined with a carrier protein.

DNA vaccines

Piece of DNA

(plasmid) genetically

engineered

to produce

specific antigens.

Experimental:

veterinary use.

Recombinant

vector vaccines

Harmless vector

expresses antigens

stimulating

immune response.

Experimental : wide

range targets.

Second generation

vaccines

Third generation

vaccines

• Immunisation is the process by which the body produces antibodies against the vaccine preventable diseases through
administration of specific vaccines.

ORGAN TRANSPLANT

• Transplantation involves the removal of damaged/injured tissues or organs from the body of a person and their substitution by
similar tissues/organs from a donor.

• Tissue matching and blood group matching are essential before undertaking any graft/transplant. Sometimes, the immune system
may reject the transplanted organ by recognising its protein as foreign. Therefore, patient has to take immuno-suppressants
(drugs) to prevent organ rejection throughout the life.

• The success of tissue and organ transplants depends on the donor’s and recipient’s human leucocyte antigens (HLA) encoded
by the HLA genes. The genes for the HLA proteins are clustered in the major histocompatibility complex (MHC), located on
the short arm of chromosome 6.

Autograft

It is grafting of one’s own tissue to another part

of the body, e.g., skin graft. It is most successful

transplantation.

Types of Organ

Transplantation

Isograft

It is transplantation from a twin brother or

sister, i.e., donor and recipient are genetically

identical.

Allograft

It is transplantation between individuals of same

species, but with different genetic background.

Xenograft

It is transplantation between animals of different

species.