I was watching the crash course episode on Immune System, brilliantly explained. But as I was re-reading my biology text book I found an additional info which I would like to share.
Along with neutrophils, macrophages and natural killer cells, there is also Complement .
Complement is a group of 20 proteins, many of which are enzyme precursors and are produced by the liver. They were named complement by Ehrlich but was discovered by Jules Bordet.
Complement proteins create pores in the plasma membrane of the microbes. Water enters the microbes. The latter burst and die.