What type of blood cell is primarily responsible for fighting infections?

Leukocytes, also known as white blood cells, are the primary cells in the immune system that are responsible for fighting infections. They play a critical role in protecting the body against both infectious disease and foreign invaders. There are several types of leukocytes, including lymphocytes (which produce antibodies), neutrophils (which engulf and destroy bacteria and fungi), and monocytes (which differentiate into macrophages and help in phagocytosis of pathogens).

These cells are actively involved in identifying, targeting, and eliminating pathogens, thus ensuring that the body can effectively respond to infections. Their presence and function are crucial for maintaining a healthy immune response, making leukocytes essential in the body's defense mechanisms.

In contrast, the other options refer to different components of the blood. Platelets and thrombocytes are involved in blood clotting and wound healing, while erythrocytes are responsible for oxygen transport throughout the body. None of these cells directly participate in fighting infections, highlighting the specialized role of leukocytes in the immune response.