• Human Papillomavirus Vaccine
• Background Information
• Process of mitosis and meiosis
• Work of a vaccine
• Virtual Lab 2: Recombinant
  DNA technology
• Revision Questions
• 

Work of a vaccine : Introduction

Immunity 免疫 is the ability of a human to fight against pathogens.  Once our body recognizes the entry of pathogens, specific immune response is triggered.  Two types of lymphocytes 淋巴細胞, B and T cells work together to fight against pathogens by the following ways:

1. T lymphocytes stimulate the B lymphocytes and phagocytes for an immune response and directly kill the infected cells by releasing cytokines 細胞激素. This immune response of killing the infected cells directly is called Cell Mediated Immune Response (CMIR) 細胞介導免疫反應.
2. B lymphocytes after contacting the pathogen differentiate into plasma cells which produce antibodies. Antibodies recognize specific part on the surface of pathogens we called antigen in a highly specific manner. After binding, antibodies eliminate the pathogen in a number of ways, for example, through agglutination 凝集作用, precipitation and neutralization. This immune response of releasing antibodies to kill and eliminate pathogens is called Humoral Immune Response (HIR) 體液免疫反應.

In the first entry of a specific kind of pathogen, primary immune response will occur after an expansion of the B and T lymphocytes. Some of the B and T lymphocytes will turn into memory cells with a longer lifespan. When the same kind of pathogen enters the body again, a much efficient and effective immune response will be triggered as a result of the expanded memory cells. This protection is called secondary immune response. The principle of vaccination is based on triggering the primary immune response of B lymphocytes and production of memory cells by using an attenuated or recombinant vaccine.

Please see the following animation which shows the detailed principles of vaccination: