Grade 12 Zoology Note

Vaccines, tissue and organ transplantation


Vaccines is a chemical substances, which is used to stimulate an immune response in the body to resist disease. The first vaccine  produced by Edward Jenner in 1776 was small pox Vaccine. Types of vaccines are as follows;

1.Killed vaccine:

These vaccine are prepared by killing  the pathogenic organisms by heat or UV-rays or alcohol for e.g. Typhoid vaccine, Cholera vaccine.


These vaccine are prepared by destroying the toxic property of the toxins. E.g. Tetanus toxoid.

3.Antibodies as vaccines:

Serum is used after a person or animal has been exposed to infection. This causes antibodies against the pathogen.  E.g. ATS,  AS.

4.Attenuated living vaccines:

The pathogen is made weakened to make it non-virulent e.g. OPB, BCG, MMR,

5.Antigen like polysaccharides:

Pneumococcii, interferon are also used in vaccines.

Classification of vaccines

Vaccines can be classified in following generation;

1.First generation vaccines:

Vaccines produced by conventional methods using whole organisms are called 1’st generation vaccines. They have both advantages as well as disadvantages.

2.Second generation vaccines:

Vaccines prepared by genetic engineering or recombinant DNA technology are called second generation vaccines. These vaccines are synthesis by high purity and potency. Also these vaccines are simpler, safer, and more effective e.g. vaccines for Hepatitis-B virus. The hepatitis-b vaccines is the first human vaccines prepared by using transgenic yeast.

3.Third generation vaccines:

Vaccines which are prepared artificially are called third generation vaccines. These vaccines have advantages of being pure and highly effective. Diphtheria is an example of this type of vaccine.

Application of vaccines:

Application of vaccines is as follows;

1.Vaccines develop immunity against infectious disease.

2.Vaccines destroy or kill the disease causative organisms.

Tissue and organ transplantation

An organ transplant is the process of moving of an organ from one body to another body. The tissue or organ which gets transplanted is called a transplant or graft. Organ that can be transplant is the recipient, and the person from whose body the organ was taken is the donor. Many people carry donor cards with them all the time, starting that they are happy for their organs to be used in a transplant operation. In human the genes that are responsible for the graft rejection called H genes or (HLA). For success of organ transplants and skin grafts require a matching of (HLA) that occur on all cells in the body. The test carried out to match the HLA antigens of the recipient is called tissue typing. IF HLA types are matched survival of transplanted organ dramatically increases.

Types of transplantation:

According to genetic relationship between donor and recipient, transplantation is classified in to four groups:


 It is the graft in which the donor and recipient is the same individual. For example; skin is taken from trunk and can be shifted to arm of same individual.


 It is a graft between genetically identical individuals such as identical twin. In this type the donor and recipient belong to same genotype.


It is a graft between genetically different members of same species. In this type the donor and recipient belong to different genotype.

4.Xenograph or heterograft:

It is the graft in which donor is of different species from that of the recipient e.g. from monkey to man or from pig to human.

Rejection of transplanted organs:

Some of the main problem is transplant rejection. The body does not accept the transplanted organ. The immune system recognizes the donor organs as foreign organ and attack it and possibly leading to transplant failure and the need immediately remove the organ from the recipient which is called rejection.

Prevention of graft rejection is as follows;

1.Slection of organs from genetically similar member.

2.The immune system can be also be suppressed  by radiation.

3. Precaution is taken according to their tissue typing.

4.Use of immunosuppressant drugs.

5.Use of monoclonal antibodies – Monoclonal antibodies.

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