The Immune System: Your Own Person Military

     This post has taken me quite awhile to write, but here is the starting point for our journey to understanding vaccines: the immune system! You can think of your immune system like your own personal army protecting you from outside threats. With this in mind, the first term that we should define is pathogen: an agent that causes disease. Your immune system is designed to protect you from pathogens. 

    Now, at first glance this definition seems pretty straight forward; however, defining a pathogen can actually be kind of a tricky process.  For example, staphylococcus aureus is normally a pretty harmless skin bacteria, but if your skin gets damaged or the staph gets into a spot it really shouldn't be, now it can cause disease. This means that staph is not always a pathogen. This also means that it can take awhile for your immune system to recognise a pathogen is present and thus the infection can take root before your immune system can respond, and thus you get something the picture on the right, which is an MRSA infection.



      The idea with vaccines is to get your immune system to immediately recognise a pathogen and destroy it before it has a chance to cause disease. So who is involved in this very important immune army? We have antibodies, T cells, and B cells. T cells and B cells are also referred to as "white blood cells".  (The oxygen carrying blood cells are called red blood cells.) There is a difference between T cells and B cells in where they are produced and how they interact with antigens, but for simplicity, I am not going to delve into the differences. We are just going to focus on B cells and antibodies. 

Antigen: This is a marker on a cell that causes a response from your white bloods (B and T). This could be a protein on the cell membrane. Whatever it is, it tells your immune system that this cells is a foreign invader and needs to be dealt with. 

Antibodies: Little Y-shaped proteins that bind to antigens. These are specific to the antigen on a specific pathogen. They are secreted proteins. They roam around your blood system and will bind to the antigen on the pathogen they are specific for when they come across them. This marks the pathogen and allows your white blood cells to destroy it. If you have had a disease, you keep the antibodies that you formed when you were infected and it prevents you from being reinfected.  (Antibodies are also referred to as immunoglobulin or immune globulin.) 

To summarise: your white blood cells (B and T cells) are your body's Swiss army. They are exist to prevent pathogens from invading your body and killing you. When you get a disease, your white blood cells wage war, and usually win. (Again, Swiss army-fierce when engaged.) Your immune system produces antibodies that bind to specific markers on pathogens, called antigens, and this marks pathogens, making them easily removed from your body. If you have never had a disease before, you will end up creating antibodies. If you have had a disease before, then you will already have antibodies, immediately marking the disease cells and preventing you from getting it again. 

   The idea with vaccines is that you trick your immune system into thinking that it has the disease. It produces antibodies, so that when you are exposed to the actual disease, your immune system immediately marks the pathogens BEFORE they can cause disease and they are destroyed by your white blood cells. 

   I said above that your immune system usually wins, so why do we even care about this? Well, just because your immune system may win, it doesn't mean that it does not suffer some losses. For example: measles, you may not die, but you may end up losing your hearing. Mumps: you may actually lose your ability to reproduce. Polio: you may be paralysed for life. And of course, you can actually die. The flu causes over 100 000 deaths world wide every year, and that doesn't even count the millions who have died in massive flu pandemics prior to the advent of the vaccine. 

Coming Up Next: Vaccines: How They are Produced