Immunology Introduction – Jan. 9
- Microorganisms can provide us with immune protection from infectious diseases. These are called
microbiota (normal flora). Microorganisms can also cause infectious diseases. Gut microbiota is
associated with health and disease. The human body has more microorganisms than human cells.
- The aims of the human microbiome project are to map every bacterium in the body and to associate
changes in the microbiome with human health/diseases.
- Microorganisms with the potential to cause infectious disease are called pathogenic microorganisms
or pathogens. Pathogens can include bacteria, viruses, parasites, and fungi.
- Many normal flora are opportunistic pathogens, which means they can become pathogenic when
- Extracellular pathogens reside outside host cells, in the interstitial spaces, blood, lymph, and
epithelial surfaces. Intracellular pathogens (most commonly viruses) reside inside host cells, in the
cytoplasm or in vacuoles. Immune responses are different to extracellular and intracellular
pathogens. Classifying microorganisms as either an intracellular pathogen or an extracellular
pathogen is sometimes incorrect because many pathogens have both an extracellular and
intracellular phase. For example, viral entry into a host cell involves a transition from the
extracellular to the intracellular space.
- The immune system is the body’s defense system that protects us against pathogens. Immunology
comes from the latin word immunitas, which means freedom from infectious diseases. The concept of
immunity from disease dates back to Greece in the 5 century BC by Thucydides in reference to
Athenians who had become immune to the plague. No one was attacked a second time, never at least
fatally. People who are exposed to a pathogen and recover develop immunity against subsequent
attacks of the same pathogen.
- How does the immune system work?: 1. Recognize pathogen. 2, Eliminate pathogen from your body.
3. Minimize the damage they cause.
- Microorganisms have the advantage of reproducing and evolving extremely quickly (ex. HIV). Disease
occurs when we are unable to mount an effective immune response against pathogen.
- The main defences of our immune system are cells and soluble molecules. Cells include some tissue
cells and white blood cells (leukocytes).