Which type of blood cell primarily fights infection in the body?

White blood cells are the blood cells that primarily fight infection in the body.

Also called leukocytes, white blood cells are immune-system cells that recognize, attack, or help coordinate defenses against pathogens and other foreign substances. They include several specialized groups, including granulocytes, lymphocytes, and monocytes. Neutrophils can rapidly respond to many bacterial infections, while lymphocytes include B cells and T cells that support antibody production and targeted immune responses.

White blood cells are made mainly in the bone marrow and travel through the blood, lymphatic system, and tissues. Unlike red blood cells and platelets, they contain nuclei, reflecting their more complex cellular functions. Their numbers can rise during infection or inflammation, although a high count does not by itself identify the exact cause.

“Plasma cells” are not a separate broad blood-cell category in the same way; they are specialized B cells that produce antibodies and are found mainly in tissues. Platelets help blood clot, while red blood cells carry oxygen. Those cells are vital, but they are not the body’s primary infection fighters.