Dr Maxwell Adeyemi

The immune system fight germs and foreign substances in the body and it is made up of two parts that work closely together by taking on different tasks.

The innate immune system

This is the body's first line of defence against germs entering the body. It responds in the same way to all germs and foreign substances hence it is often called general or 'non-specific' immune system. It acts quickly and ensures germs are detected and destroyed within a short space of time, but it has only limited power to stop germs from spreading.

The innate immune system consists of:

• Skin and mucous membrane, which form physical barriers against germs, also consist of chemicals like acids, enzymes and mucus that prevent germ entry.

• Immune system or defence cells are activated when germs get past the physical barrier, these cells cause inflammation, blood vessels get wider and more permeable, the area affected get swollen, hot and red. A fever may develop, more blood vessels expand, and more immune cells arrive the area. Scavenger cells known as phagocytes, a special kind of white blood cells or leucocytes attack the germs and neutralise them.

• Protein and enzymes are usually released to help the innate cells. Up to nine different enzymes and inflammatory substances are released and allows the immune system responses to escalate quickly to destroy germs.

• Natural killer cells destroy germs and infected cells by using cell toxins.

The adaptive or acquired immune system

This takes over when the innate system is unable to destroy the germ. Otherwise known as specific or acquired immune system, it specifically targets the type of germ causing the infection. It first identifies the germ, then attacks it. This immune system is slow to respond but is very accurate and has the advantage of being able to remember germs so that if it encounters the specific germ again, it will respond swiftly to neutralise or destroy it.

The adaptive immune system consists of:

• T-cells are produced in the bone marrow and stored in the thymus gland. They can be specialised into cytotoxic T-cells that detect and destroy germs and T-helper cells that use chemical messengers to activate other immune cells that start the adaptive immune system. They then become memory T-cells that can remember cells after infections has been defeated. The immune system can produce a matching T-cell type for each germ, once a germ attaches to the matching T-cell, it multiplies rapidly creating more T-cell specialised to that germ.

• B-cells are produced in the bone marrow and matures into specialised cells. B-cells are activated by T-helper cells, they also multiply and transform into plasma cells, which quickly produce large amounts of antibodies. Some of the activated B-cells transform into memory cells and become part of the adaptive immune system. The various adaptive immune system communicates directly or by chemical messengers such as cytokines - sm