The immune system

What is an immune system?

How does the body fight infection? When germs, such as bacteria or viruses, invade the body, they attack and proliferate. This invasion, called an infection, is what causes illness. The immune system uses several tools to fight infection. Blood contains red blood cells, for carrying oxygen to tissues and organs, and white or immune cells, for fighting infection. These white cells primarily consist of:

• Macrophages are white blood cells that swallow up and digest germs, plus dead or dying cells. The macrophages leave behind parts of the invading germs called antigens. The body identifies antigens as dangerous and stimulates antibodies to attack them.
• B-lymphocytes are defensive white blood cells. They produce antibodies that attack the antigens left behind by the macrophages.
• T-lymphocytes are another type of defensive white blood cell. They attack cells in the body that have already been infected.

The first time the body encounters a germ, it can take several days to make and use all the germ-fighting tools needed to get over the infection. After the infection, the immune system remembers what it learned about how to protect the body against that disease.

The body keeps a few T-lymphocytes, called memory cells, that go into action quickly if the body encounters the same germ again. When the familiar antigens are detected, B-lymphocytes produce antibodies to attack them. link

Boost your immune system

• lack of sleep can lead to higher levels of a stress hormone. It may also lead to inflammation in your body.
• moderate exercise of 30 minutes per day can help the body fight off infection.
• eating a wide variety of brightly coloured fruit and vegetables which are rich in vitamin C, E, beta-carotene and zinc are good for your immune system

Naturally acquired immunity

This is immunity from having acquired the disease itself. Some people think that naturally acquired immunity is better than immunity provided by vaccination. However, infections can cause acute complications and may cause death.

During the last 3 months of pregnancy, antibodies from the mother are passed to her unborn baby through the placenta. This type of immunity is called passive immunity because the baby has been given antibodies rather than making them itself. Newborn immunity is temporary, lasting about 2 months, therefore it is important to commence childhood immunisations at this time.

Immunity passports

According to the World Health Organisation (WHO) “there is currently no evidence that people who have recovered from COVID-19 and have antibodies are protected from a second infection”.

WHO have warned against the issuance of “immunity passports to people who have been sick with COVID-19 on the assumption that they will be immune from reinfection. “As of 24 April 2020, no study has evaluated whether the presence of antibodies to SARS-CoV-2 confers immunity to subsequent infection by this virus in humans,” the paper said, using the formal name for the virus which causes COVID-19. link