What are the first line of defense in the immune system?

Question

What are the first line of defense in the immune system?

Answer 1

It differs from organism to organism, again the answer is on wikipedia. basically, anything the pathogen is first in contact with that can kill it will be the first line of defense.

Several barriers protect organisms from infection, including mechanical, chemical and biological barriers. The waxy cuticle of many leaves, the exoskeleton of insects, the shells and membranes of externally deposited eggs, and skin are examples of the mechanical barriers that are the first line of defense against infection.[5] However, as organisms cannot be completely sealed against their environments, other systems act to protect body openings such as the lungs, intestines, and the genitourinary tract. In the lungs, coughing and sneezing mechanically eject pathogens and other irritants from the respiratory tract. The flushing action of tears and urine also mechanically expels pathogens, while mucus secreted by the respiratory and gastrointestinal tract serves to trap and entangle microorganisms.[6]

Chemical barriers also protect against infection. The skin and respiratory tract secrete antimicrobial peptides such as the β-defensins.[7] Enzymes such as lysozyme and phospholipase A2 in saliva, tears, and breast milk are also antibacterials.[8][9] Vaginal secretions serve as a chemical barrier following menarche, when they become slightly acidic, while s***n contains defensins and zinc to kill pathogens.[10][11] In the stomach, gastric acid and proteases serve as powerful chemical defenses against ingested pathogens.

Within the genitourinary and gastrointestinal tracts, commensal flora serve as biological barriers by competing with pathogenic bacteria for food and space and, in some cases, by changing the conditions in their environment, such as pH or available iron.[12] This reduces the probability that pathogens will be able to reach sufficient numbers to cause illness. However, since most antibiotics non-specifically target bacteria and do not affect fungi, oral antibiotics can lead to an “overgrowth” of fungi and cause conditions such as a vaginal candidiasis (yeast infection).[13] There is good evidence that re-introduction of probiotic flora, such as pure cultures of the lactobacilli normally found in yoghurt, helps restore a healthy balance of microbial populations in intestinal infections in children and encouraging preliminary data in studies on bacterial gastroenteritis, inflammatory bowel diseases, urinary tract infection and post-surgical infections.[14][15][16]

Answer 2

I'm gonna keep this real concise.....

First line is nonspecific defense. Helps prevent pathogens from entering the body. These include:

Skin that blocks pathogen

Mucous membranes that release mucus and trap microbes.

Cilia in the respiratory system that sweep out mucus with its trapped microbes.

Stomach acid that kills germs that enter through the nose and mouse

Answer 3

physical barrier presented by skin and mucous membranes of the body.

Answer 4

I think it's your skin

Answer 5

The tonsils...Too bad so many doctors take out tonsils at the least little bit of trouble...They are wonderful filters..

Answer 6

white blood cells i think