This chapter is all about the immune system and vaccines! 

Each type of cell has specific molecules on its surface that identify it. These molecules include proteins and enable the immune system to identify pathogens, cells from other bodies of your species, abnormally growing body cells and toxins. In this chapter, you will learn about antigens and antibodies, relating them to protein structure that was taught in chapter 1. You will be learning about how the cells of your immune system work together to combat pathogens.