Chapter 26, Problem 1SA

Summary Introduction

To review:

The three ways in which the immune system combats pathogens.

Introduction:

The immune system is said to have three lines of defense – physical, non-specific and specific.

Explanation of Solution

The immune system has levels at which it defends the body against pathogens.

Physical barriers make up the first level of defense, by preventing the pathogens from entering and establishing infection in the body. The skin, hair in the nose and ears, and the mucus membranes are examples of physical barriers. They also secrete some chemicals that stop the growth of pathogens.

Non-specific immunity refers to the immune cells that attack all foreign objects, without specifically attacking one type of pathogen. This type of defense is rapid and is seen in almost all multicellular organisms. This is also called innate immunity since we are born with it.

Specific immunity refers to the cells and molecules that recognize specific pathogens, remember them and attack them strongly when they re-enter the body. This is slow to activate, but offers the best protection once activated. This is also called adaptive immunity.

Conclusion

Physical barriers are the surfaces such as the skin, hair and the mucus membranes, that prevent the entry of pathogens into the body. Non-specific immunity refers to the immune cells that recognize any foreign object and attack it rapidly, without being specific to one pathogen. Specific immunity refers to the immune cells and molecules that recognize and fight off specific pathogens, that the body has been previously exposed to.