Page:Bacteria, why do they make me sick?.pdf/18



As mentioned, a bacterial infection doesn’t always lead to disease and this is thanks to our immune system, which, roughly, is able to distinguish self from nonself.

There are two types of immunity: innate or natural immunity (IIS) and the acquired immunity (AIS).

• It’s the first line of defense against invasive microorganisms (bacteria, viruses, and fungi).

• It is present since birth; it is nonspecific and lacks memory.

The IIS has three components:

• Physical and chemical barriers; such as skin, cilia, mucosae and secretions. By continuous cleaning, they protect us and prevent the foreign particles entering the body.

• The humoral component is composed of antibodies and the complement system.

• The cellular component, which is the cells that are part of the Innate Immune System: neutrophils, eosinophils, basophils, mast cells, and Natural Killers lymphocytes (NK lymphocytes).

• Acquired immunity is not present at birth, it increases with age and it is specific, and it has a memory. This is why it is also called adaptative.

• It is composed of antibodies, T lymphocyte receptors and the molecules of the major histocompatibility complex.

In general, the innate and acquired immune responses are not activated independently. Their optimal performance is when they complement each other.

In particular, the AIS’ antibodies are able to direct the IIS’ components toward the relevant objects.