The immune system's main purpose is to defend the body against harmful microorganisms, such as bacteria, viruses, and parasites.

White blood cells, specifically lymphocytes, are responsible for recognizing and attacking foreign invaders through various mechanisms.

Antibodies are proteins produced by the immune system to neutralize and eliminate foreign substances, such as bacteria and viruses.

Antigens are molecules that trigger an immune response by activating immune cells, such as lymphocytes, to recognize and attack foreign invaders.

Vaccination introduces a weakened or inactivated form of a pathogen into the body, allowing the immune system to develop immunity without causing illness.

Adaptive immunity, specifically through memory cells, provides long-term immunity by remembering and responding to specific pathogens encountered in the past.

Macrophages are phagocytic cells that engulf and destroy foreign particles, such as bacteria, viruses, and cellular debris.

Humoral immunity involves the production of antibodies by B cells, which are specific proteins that recognize and neutralize foreign antigens.

Cytokines are small proteins that regulate immune cell activity, communication, and differentiation, playing a crucial role in coordinating immune responses.

Active immunity is acquired through exposure to an antigen, leading to the production of antibodies by the immune system, while passive immunity is acquired through the transfer of antibodies from another individual.

T cells, specifically cytotoxic T cells, are responsible for cell-mediated immunity by directly killing infected cells and tumor cells.

The complement system is a group of proteins that work together to destroy infected cells, promote inflammation, and enhance the effectiveness of antibodies.

Innate immunity provides immediate protection against infections through physical barriers, chemical mediators, and phagocytic cells, without the need for prior exposure to the pathogen.

Dendritic cells are specialized antigen-presenting cells that capture and process antigens, then present them to immune cells, such as T cells, to initiate an immune response.

Memory cells are long-lived lymphocytes that remember and respond to specific pathogens encountered in the past, providing rapid and robust immune responses upon re-exposure.