WBC's that stands for white blood cells, that are cells of the immune system. It helps to protect the body from various infectious diseases. There are different types of white blood cells in the body like T cells, B cells, monocytes etc. And is circulated in the body by the circulatory system and thus helps in the recovery from the infection.
Thus, immune and circulatory are two organ systems that are involved in the recovery of the infection.
The population will continue to grow but as we grow so does pollution. Some would need vaccines to cure simple diseases like the flu but what if there would not be enough?
