What are the different types of immunity?

The different types of immunity are innate immunity, adaptive immunity, passive immunity, and humoral immunity.

Innate immunity, also known as natural or non-specific immunity, is the first line of defence against pathogens. It is present from birth and provides immediate but general protection against any foreign invaders. This type of immunity includes physical barriers like skin and mucous membranes, as well as internal defences such as fever, inflammation, and phagocytic cells that engulf and destroy pathogens. Innate immunity does not have a memory response, meaning it responds to pathogens in the same way regardless of whether the body has encountered them before.

Adaptive immunity, also known as acquired or specific immunity, is not present at birth but is developed throughout life. It provides a targeted response to specific pathogens that the body has previously encountered. This type of immunity involves lymphocytes (B-cells and T-cells) and has a memory response, allowing for a quicker and more effective response to pathogens that the body has been exposed to before. Adaptive immunity can be further divided into humoral and cell-mediated immunity.

Humoral immunity is a type of adaptive immunity that involves B-cells producing antibodies in response to an antigen (foreign substance). These antibodies circulate in the blood and lymph, binding to the antigen to neutralise it or mark it for destruction by other immune cells. This type of immunity is particularly effective against bacteria and viruses in body fluids.

Passive immunity is another type of immunity where antibodies are obtained from another source, rather than being produced by the individual's own immune system. This can occur naturally, such as the transfer of antibodies from a mother to her baby through breast milk, or artificially, such as through the injection of antibodies. Passive immunity provides immediate but temporary protection, as the antibodies are eventually broken down and do not contribute to immune memory.

In summary, the immune system is a complex network of cells, tissues, and organs that work together to defend the body against harmful pathogens. It achieves this through various types of immunity, each with its own unique characteristics and functions.