Immunity (medical)

Immunity refers to the biological mechanisms that defend an organism against disease. This complex system is made up of cells and proteins that work together to protect the body from potentially harmful invaders such as bacteria, viruses, and parasites. Immunity can be broadly classified into two types: innate (or natural) immunity and adaptive (or acquired) immunity.

Innate Immunity

Innate immunity is the first line of defense against pathogens. It is non-specific and responds to pathogens in a generic way. This type of immunity is present at birth and provides immediate but temporary protection. Components of innate immunity include physical barriers like skin and mucous membranes, and internal defenses such as phagocytes, natural killer cells, and the complement system.

Adaptive Immunity

Adaptive immunity, on the other hand, is a specialized type of immunity that develops over time. It involves the activation of lymphocytes, which respond to specific pathogens and remember them for future encounters. This results in a stronger and quicker response upon subsequent exposures, a phenomenon known as immunological memory.

Immune Response

The immune response is the reaction of the immune system to foreign substances. It involves a complex network of interactions between various cells and molecules. The immune response can be divided into the humoral response, which is mediated by antibodies, and the cell-mediated response, which involves T cells.

Immunodeficiency

Immunodeficiency occurs when the immune system's ability to fight infectious diseases is compromised or entirely absent. This can be due to genetic disorders, infections, or treatments such as chemotherapy. People with immunodeficiency are more susceptible to infections and may have difficulty recovering from them.

Immunization

Immunization is a way to artificially induce immunity against a specific disease. This is usually achieved by introducing a weakened or dead form of the pathogen, or a part of it, into the body. This stimulates the immune system to produce a response, including the production of antibodies, without causing the disease itself.

File:Immune System Diagram.jpg

Diagram of the human immune system

See Also

• Autoimmunity
• Immunology
• Vaccine
• Allergy