There are two subsystems within the immune system
1. Innate (non-specific) immune system
2. Adaptive (specific) immune system.
Both of these subsystems are closely linked and work together whenever a germ or harmful substance called a pathogen triggers an immune response.
The innate immune system provides a general defense against harmful germs and substances, so it’s also called the non-specific immune system. It mostly fights using immune cells such as natural killer cells and phagocytes (“eating cells”). The main job of the innate immune system is to fight harmful substances and germs that enter the body, for instance through the skin or digestive system.
The adaptive (specific) immune system makes antibodies and uses them to specifically fight certain germs that the body has previously come into contact with. This is also known as an “acquired” (learned) or specific immune response.Because the adaptive immune system is constantly learning and adapting, the body can also fight bacteria or viruses that change over time.
Cell lineages below indicate the variety of cells involved in any response to an injury / pathogen. Each cell expresses a variety of proteins on its cell surface which interact with many cell receptors and chemicals within and outside cells.
"Antibodies" are produced by plasma B cells are a common marker of measuring an immune response to infection or vaccination, of which there are 5 and more types being characterised.
Cell lineages are derived from where the cells develop
Immunopaedia - An excellent resource on all updates and developments in immunity
Immunopharmacology - All the cells and mechansims involved in immune cell regulation