The immune system's primary function is to protect the body from harmful substances, such as bacteria, viruses, and toxins.

The cell-mediated immune response is responsible for attacking and destroying infected cells. It involves the activation of T cells, which can directly kill infected cells or release chemicals that attract other immune cells to the site of infection.

The humoral immune response involves the production of antibodies, which are proteins that can bind to and neutralize pathogens. Antibodies are produced by B cells, which are activated by antigens.

Macrophages are phagocytic cells that engulf and destroy foreign particles, such as bacteria, viruses, and cellular debris. They play an important role in the innate immune response.

B cells are responsible for producing memory cells, which are long-lived cells that can quickly respond to a pathogen that the body has encountered before.

The thymus gland is responsible for maturing T cells, which are a type of white blood cell that plays a crucial role in the adaptive immune response.

The adaptive immune response is responsible for providing long-term protection against infection. It involves the activation of memory cells, which can quickly respond to a pathogen that the body has encountered before.

Cytokines are small proteins that regulate the immune response. They are produced by immune cells and can act on other immune cells to activate or suppress their function.

Mast cells are responsible for releasing histamine and other inflammatory mediators, which are involved in the inflammatory response.

The spleen is responsible for filtering blood and removing old or damaged red blood cells, as well as foreign particles and pathogens.

The innate immune response is responsible for providing immediate protection against infection. It involves the activation of physical barriers, such as the skin and mucous membranes, as well as the production of antimicrobial substances, such as interferons.

The lymph nodes are responsible for filtering lymph and removing foreign particles and pathogens. They also contain immune cells, such as lymphocytes, which can activate an immune response.

The bone marrow is responsible for producing natural killer cells, which are a type of white blood cell that can kill infected cells and tumor cells.

The complement system is a group of proteins that work together to enhance the activity of antibodies and promote the destruction of pathogens.

The cell-mediated immune response is responsible for providing protection against intracellular pathogens, such as viruses and bacteria that live inside cells.