What is the composition of blood?

Blood consists of 4 different elements: 

1. 55% is PLASMA 
   
2. other 45% are 3 different components: 
   

• red blood cells
  
• white blood cells
  
• platelets 

The main components we will focus on today are: white blood cells. If you think about white blood cells, they themselves have lots of different types of cells present within them. Their function is basically to protect us against pathogens. They're part of the so-called immune system. The main players all work together in harmony to make sure we stay healthy and disease free! About 25 per cent of the white blood cells are lymphocytes (B and Tcells). These lymphocytes produce soluble proteins called antibodies. Antibodies basically help in the recognition of "outside material" that enter our body, namely pathogens. So antibodies will find an antigen (these are substances found on the surface of pathogens) and attach to it. Different antibodies will attach to different antigen, this way you have more specificity. Antibodies can surround the pathogen and basically cause it to die in various different ways, but mostly by tagging them to get killed by phagocytes (which make up the other 70% of the immune system) and macrophages (another type of cells part of the immune system).