IMMN

Innate and adaptive immune responses may operate independently or collaboratively to eliminate infection

Student name: Xinyi Yang
Word count: 1470

Introduction
Human body contains approximately 1013 human cells and 1014 bacterial, protozoan and fungal cells (Immunity, 2007). To defense against those pathogens, our body generate three levels of defense: (1) anatomic barriers; (2) innate immune system and (3) adaptive immune system. The first level of defense involves the inhibition effects of skin, mucus secretion of the respiratory tract, low pH of stomach, etc. If pathogens do get through the physiological barrier, the innate and adaptive immune system come into play.
Innate immunity is widely exist in all animal types, whereas, adaptive immunity only developed in vertebrates. It is also much less specified than that of adaptive immunity and does not include memory cells. Some major differences between innate and adaptive immunity are shown in table 2.

innate immunity adaptive immunity evolutionary origin all animals vertebrates secretion cells phagocytes lymphocytes secretion molecules complement, cytokines antibody, cytokines specificity broad high rate of action rapid slow development of memory no yes Table 2. Main differences of innate and adaptive immunity.
The infectious diseases remains one of the major causes of deaths, especially in the developing countries (see table 1). Therefore, understanding the mechanism of immune responses against infection is vital in diagnosis development.
It is only till recent that people discovered the link between innate and adaptive immunity. This essay will briefly introduce the innate immune system and discuss how the adaptive immunity might be regulated by the innate immune system.

deaths / year
Causes of death developed countries developing countries circulatory disease
5900000
6500000 cancer 2300000
2500000
infectious disease
500000
16500000
Table 1. Comparison of deaths caused by three

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