What are components of the first line of defense?

Answer 1

The body's first line of defense against pathogens uses mostly physical and chemical barriers such as sweat, skin, tears, mucus, stomach acid, and so on. Our skin and other membranes which line the body passages are fairly effective in keeping most pathogens out of the body. Mucus can trap pathogens, which are then washed away or destroyed by chemicals. Tears, sweat, and saliva all contain chemicals to destroy pathogens to some extent.

There's multiple ways to organize the body's defenses. One way splits them into two parts: specific and nonspecific. Specific, also known as adaptive, is the last line of defense. This describes anything that targets the specific antigen, and not foreign substances in general. Specific includes lymphocytes, their antibodies, and the rather complex system that allows your body to become immune to certain invaders.

The non-specific, or innate, immune system is the first line. This includes the first line of defense as described in the first paragraph, but also includes non-specific cells such as macrophages and neutrophils, which will eat and destroy just about anything it encounters that isn't a part of your body. Also included are the complement system, inflammatory response and interferons, which are left for another question.

Answer 2

the skin