The **immune system** functions as a defense system that fights pathogens and prevents infection in the body. The immune system recognizes, attacks, damages, destroys and eventually remembers the pathogen that enters the body. There are two general categories of the immune system: **nonspecific defense** and **specific defense**.

The **nonspecific defenses** cannot distinguish one threat from another. However, they act as the first line of defense by the body (like an outer gate of a castle), hence preventing the entrance of pathogens. Two known nonspecific defenses are the **skin** and **inflammatory responses**.

The **immune system** protects us from pathogens. The immune system produces specialized cells that recognize and fight against invading pathogens. As the specialized cells fight the pathogens, it also creates *a database* or response that remembers the pathogen for future invasion and protection.

When a cell becomes infected by a virus, the infected cells produce interferons to block the virus from synthesizing more viral proteins and also block viral replication. Interferons give the immune system more time to respond by slowing down the rate of infection.

**Antigens** are pathogens such as viruses and bacteria that elicit an immune response. One specialized cell of the immune system is the plasma cell. Plasma cells release antibodies that are able to recognize, bind, and attack a particular antigen.

Differences:
Active immunity refers to the body’s response by producing antibodies to counter an unknown pathogen. On the other hand, passive immunity refers to the body’s response that involves the help of antibodies, which are acquired outside of the body.

Similarities:
Both active immunity and passive community can develop by natural means or by repeated exposure.

Active immunity refers to the body’s response by producing antibodies to counter an unknown pathogen. On the other hand, passive immunity refers to the body’s response that involves the help of antibodies, which are acquired outside of the body. Both active immunity and passive community can develop by natural means or by repeated exposure.