What type of cell is produced by the spleen to defend against foreign cells?

The correct response highlights the role of white blood cells in defending against foreign cells. The spleen is an integral part of the immune system and plays a crucial role in producing and storing various types of white blood cells, particularly lymphocytes. These cells are essential for identifying and attacking pathogens such as bacteria and viruses, contributing to the body's immune response.

While antibodies are indeed vital for immune defense, they are produced by a specific type of white blood cell known as B cells, which are found in the spleen. Therefore, focusing on white blood cells as the primary defenders against foreign cells encompasses the broader function of the spleen in immune response.

Red blood cells and platelets play important roles in the body—red blood cells in oxygen transport and platelets in clotting—but they do not participate directly in the immune response against foreign cells. This distinction emphasizes why the production of white blood cells is the most relevant and accurate answer when discussing the spleen's immune function.