Developmental Immunology is a branch of medical science that deals with the study of factors responsible for development of immune cells and organs in an organisms body. In newly born babies, immune system is still in developing condition, while with aging, the system gets depressed. Hence, there are several factors that are responsible for an active immune system in human body which includes age, type of antigen, maternal factors, etc. In case of neonates, the body immune cells like lymphocytes and monocytes are not fully active. Hence, when they get in contact to the foreign cells and antigens, their phagocytic activity gets impaired. Maternal milk carries various important factors like antibodies that are needed for an active innate immunity in neonates. These antibodies actually help the new born babies to survive for months without any external vaccination. Developmental immunology focuses to deal with the above circumstances. It forms an important part of immunological study. The journals related to this portion of science encourage new and young scientists to work on the causes and consequences of immunological diseases that occur due to improper development of immune system.