The Health Diva

The most common disease-causing microbes are bacteria, viruses, and parasites. Each uses a different tactic to infect a person, and, therefore, each is thwarted by different components of the immune system.

Most bacteria live in the spaces between cells and are readily attacked by antibodies. When antibodies attach to a bacterium, they send signals to complement proteins and phagocytic cells to destroy the bound microbes. Some bacteria are eaten directly by phagocytes, which signal to certain T cells to join the attack.

All viruses, plus a few types of bacteria and parasites, must enter cells of the body to survive, requiring a different kind of immune defence. Infected cells are able to alert T lymphocytes to destroy the infected cells. Antibodies also can assist in the immune response by attaching to and clearing viruses before they have a chance to enter cells.

Parasites live either inside or outside cells. Intracellular parasites such as the organism that causes malaria can trigger T cell responses. Extra cellular parasites are often much larger than bacteria or viruses and require a much broader immune attack.

The role of the immune system is very complex and to be honest something we largely take for granted until something goes wrong and we have recurrent infections, find it difficult to shift a virus, or start to develop allergic reactions.