Which cells are primarily responsible for fighting infections?

White blood cells, also known as leukocytes, are the primary cells responsible for fighting infections in the body. Their main role is to identify and eliminate pathogens such as bacteria, viruses, and other foreign substances that can cause diseases. There are several different types of white blood cells, including neutrophils, lymphocytes, monocytes, eosinophils, and basophils, each with specialized functions in the immune response.

These cells are crucial to the immune system as they not only attack and destroy invaders but also help in coordinating the overall immunity response by signaling other immune cells. For instance, lymphocytes, which include T cells and B cells, are particularly important in identifying specific pathogens and developing targeted responses, including the production of antibodies.

The other options involve different functions: red blood cells are primarily responsible for transporting oxygen and carbon dioxide, platelets play a critical role in blood clotting, and plasma cells are a type of B cell that specifically produces antibodies. While plasma cells engage in fighting infections by producing antibodies, they are a subset of white blood cells. Therefore, the most comprehensive answer regarding the primary cells responsible for fighting infections remains white blood cells.