Which component of the blood is primarily responsible for immune responses?

White blood cells, or leukocytes, are primarily responsible for immune responses in the body. They play a crucial role in identifying and combating pathogens such as bacteria, viruses, and other foreign substances. There are several types of white blood cells, including lymphocytes, neutrophils, and macrophages, each with specific functions in the immune system. For instance, lymphocytes are key players in adaptive immunity, recognizing specific antigens and facilitating targeted immune responses. Neutrophils and macrophages are part of the innate immune system, acting quickly to engulf and destroy pathogens.

These cells circulate throughout the body, moving from the bloodstream to tissues where they can encounter and respond to infections. In contrast, red blood cells are primarily responsible for transporting oxygen from the lungs to the rest of the body and returning carbon dioxide to the lungs. Platelets are involved in blood clotting, and plasma proteins primarily function in transport and regulation, such as maintaining osmotic pressure. While other components of blood have their own important roles, it is the white blood cells that are integral to the immune response.