This term refers to the various ways that the body protects itself from many types of pathogens, without having to "recognize" them. The first line of defense in nonspecific immunity (the outermost layer) consists of the methods of protection:
- Mechanical - examples include the skin, which acts as a barrier, and the sticky mucus on mucous membranes, which serves to trap pathogens.
- Physical - examples include coughing, sneezing, vomiting, and diarrhea. Although not pleasant, these serve to expel pathogens that have gotten past the initial barriers.
- Chemical - examples include tears, saliva, and perspiration. These have a slightly acidic nature that deters pathogens from entering the body while also washing them away. In addition, stomach acids and enzymes serve to kill germs.
The second line of defense in nonspecific immunity comes into play if the pathogens make it past the first line. Defensive measures include certain processes, proteins, and specialized cells. Defensive processes include the following:
- Phagocytosis - pathogens that make it past the first line of defense and enter into the bloodstream may be consumed by neutrophils and monocytes.
- Inflammation - acquiring its name from its properties, this is a protective response to irritation or injury. The characteristics (heat, swelling, redness, and pain) arise in response to an immediate vasoconstriction, followed by an increase in vascular permeability. These provide a good environment for health. If caused by a pathogen, the inflammation is called an infection.
- Pyrexia - when infection is present, fever may serve a protective function by increasing the action of phagocytes and decreasing the viability of certain pathogens.
The protective proteins are part of the second line of defense. These include interferons, which get their name from their ability to "interfere" with viral replication and limit a virus's ability to damage the body. A second protein type, the complement proteins, exist as inactive forms in blood circulation that become activated in the presence of bacteria, enabling them to lyse (destroy) the organisms.
Finally the last of the "team" in the second line of defense are the natural killer (NK) cells. This special kind of lymphocyte acts nonspecifically to kill cells that have been infected by certain viruses and cancer cells.
(Useful for UPSC General Studies, APPSC Group 1 Group 2 , Mains Material, Paper 1, Paper 4 Section 1 Section 2 Section 3, ROLE AND IMPACT OF SCIENCE AND TECHNOLOGY IN THE DEVELOPMENT OF INDIA, GENERAL AWARENESS WITH THE MODERN TRENDS IN LIFE SCIENCES, DEVELOPMENT & ENVIRONMENT PROBLEMS)