Immunity is the body’s ability to resist and fight off infections, diseases, and other foreign substances that enter the body. The immune system is a complex network of specialized cells, tissues, and organs that work together to defend the body against harmful invaders such as viruses, bacteria, fungi, and parasites.

There are two types of immunity – innate (natural) and acquired (adaptive). Innate immunity is the first line of defense and includes physical and chemical barriers such as the skin, mucous membranes, and stomach acid. It also includes non-specific immune responses such as inflammation and fever.

Acquired immunity, also known as the adaptive immune system, develops over time as the body encounters new foreign substances. It involves the production of specific antibodies and immune cells that are able to recognize and attack these substances. Acquired immunity can be either active or passive. Active immunity is gained through natural exposure to a pathogen or through vaccination, where the body produces its own antibodies. Passive immunity is given to a person through the transfer of pre-made antibodies, such as through breastmilk or immunoglobulin injections.

A healthy immune system is essential for maintaining overall health and preventing diseases. However, certain factors can weaken the immune system, such as stress, poor diet, lack of sleep, and certain medical conditions. Immunodeficiency disorders, where the immune system fails to function properly, can also lead to increased susceptibility to infections and diseases.