Basic Immunology Introduction
Intro
Our blood is so energy rich that any quickly dividing organism could use all of it within hours and would kill us. Therefore, our resources have to be defended against any form of cell that tries to steal it. These cells can be either invaders that got across the skin (bacteria, worms, insects). They can also be our own cells that might suddenly use too much energy (infected by a virus or with a mutated cancer-genome).
Immunology, like any part of biology, is daunting at first because of the many strange technical terms, many of them derived from ancient Greek. Learning about the immune system revolves mostly around many different types of cells that are transported by our blood together with the red blood cells. When you spin blood in a centrifuge, you get three layers: red, white and transparent water (called "plasma"). The immune system cells accumulate in a white layer above the red blood cells. The different cells of the immune system are called white blood cells or leukocytes (leuko=white, cyte=cell).
They travel towards the organs in the blood vessels and return via the lymphatic system (lympha=water), a network of conduits through the whole body that empties into the heart, from where they re-enter the blood stream. There are eight major types of cells and we will not cover all of them here. The most difficult part of immunology is the communication between the different cell types, but we will not cover this here either.
Some of these cell types (like macrophages, neutrophils or natural killer cells) can destroy other cells with various means (not covered here). The tricky part is how do these cells recognize foreign cells or mutated body cells. This task is accomplished by one type of cells, called the lymphocytes (lympho=related to the lymphatic system, cyto=cell). Lymphocytes can be divided into B-cells, produced in the bone marrow, and T-cell, produced in the thymus.
T-Cells check body cells and try to recognize the "unusual" ones by scanning them with special receptors on their cell surface. If they think that the cell is "unusual", they will then recruit other cells to kill them, induce them to commit suicide or kill them directly.
B-Cells recognize non-body stuff, which is called antigen. They do this by either binding to a part of the the antigen called epitope with receptors on their cell membrane. Or they can secrete these receptors in the form of antibodies into the blood (or mucus) where the antibodies will bind themselves to antigen, without any other cell around.
