One recurrent, common theme with ASVAB science biology is the appearance of different cell types.
In the cardiovascular system we learned about red blood cells and platelets; how the former transport oxygen around the body whilst assisting the elimination of carbon dioxide, and how the latter is involved in plugging any cuts or wounds we may have sustained.
In the immune system, the predominant cell type is the white blood cell. Scientifically, that cell is referred to as a leucocyte.
There are many different types of leucocyte, each of which with a different but complementary function. These include:
- Phagocytes – macrophages and neutrophils
- Granulocytes – eosinophils, basophils and mast cells
- B-cells and T-cells
Thankfully, you are not required to have an in-depth understanding of each of these cell types. What you do need to know, though, is how these cells work together to protect the immune system.
We mentioned the word ‘phagocytes’ above. Phagocytosis is an important immunological tool; the name given to the process through which white blood cells eat, or break down, harmful cells.
These harmful cells may be disease-causing – in which case they are known as pathogens.
Mast cells play an important role in allergy.
Many people experience allergic reactions. The symptoms of an allergic reaction – such as a runny nose – are mediated by mast cells. The cause of the allergic reaction – such as pet dander – is known as the antigen. When the human body is exposed to that antigen, mast cells release histamine and it’s through histamine that we experience the allergic, inflammatory response.
You may have heard of antihistamines – which work by blocking the effects of that histaminereleased from mast cells.
Finally, we must talk about natural killer cells (NK cells). These are rapidly acting cells that directly seek out, and kill, very harmful cells in the body. This includes tumor cells as well as viral or bacterial cells.
NK cells have a much faster response than many other elements of the immune response. Typically, once the body is exposed to a pathogen or tumor cell, NK cells respond within 72 hours. That may appear to be a long time but, for the immune system, is quite rapid.