B1.1.2 How our bodies defend themselves against diseases

Defense

Microorganisms that cause infectious disease are called pathogens.

Bacteria and viruses may reproduce rapidly inside the body and may produce poisons (toxins) that make us feel ill. Viruses damage the cells in which they reproduce.

The body has different ways of protecting itself against pathogens.

White Blood Cells

White blood cells help to defend against pathogens by:

• ingesting pathogens
• producing antibodies, which destroy particular bacteria or viruses
• producing antitoxins, which counteract the toxins released by the pathogens.

Immunity

The immune system of the body produces specific antibodies to kill a particular pathogen. This leads to immunity from that pathogen. In some cases, dead or inactivated pathogens stimulate antibody production. If a large proportion of the population is immune to a pathogen, the spread of the pathogen is very much reduced.

A vaccine usually contains:

• Dead form of the pathogen
• Antigens from the pathogen
• A weakened or inactive form of the pathogen

Semmelweis

Semmelweis recognised the importance of hand-washing in the prevention of spreading some infectious diseases. By insisting that doctors washed their hands before examining patients, he greatly reduced the number of deaths from infectious diseases in his hospital.

Relieving Symptoms

Some medicines, including painkillers, help to relieve the symptoms of infectious disease, but do not kill the pathogens.

Antibiotics and Resistance

Antibiotics, including penicillin, are medicines that help to cure bacterial disease by killing infectious bacteria inside the body. Antibiotics cannot be used to kill viral pathogens, which live and reproduce inside cells.

It is important that specific bacteria should be treated by specific antibiotics. The use of antibiotics has greatly reduced deaths from infectious bacterial diseases. Overuse and inappropriate use of antibiotics has increased the rate of development of antibiotic resistant strains of bacteria.

Many strains of bacteria, including MRSA…