Fighting infection is primarily the job of white blood cells (WBCs), not red blood cells. White blood cells are part of the immune system and work to identify, attack, and eliminate pathogens like bacteria, viruses, and fungi. Red blood cells, on the other hand, are specialized for oxygen transport, not immune defense. Confusing the two types of blood cells is common, but they serve distinct roles. While both circulate in the bloodstream, only white blood cells are designed to detect and respond to infection. If you're thinking about immunity, white cells are key — but for oxygen delivery, it's red blood cells that carry the load.