What is the primary function of white blood cells?

The primary function of white blood cells is to fight infection and disease. White blood cells, or leukocytes, are a crucial part of the immune system, tasked with identifying and combating pathogens such as bacteria, viruses, and other foreign invaders. They play an essential role in immune response by recognizing harmful microorganisms, producing antibodies, and directing other immune cells to respond effectively. This defensive action not only helps to protect the body from infections but also aids in the process of healing and maintaining overall health.

In contrast, the other options describe functions performed by different types of cells: red blood cells are responsible for transporting oxygen in the blood, while certain cells in the digestive system absorb nutrients. Hormone production is generally associated with endocrine cells or glands, not white blood cells. Understanding the role of white blood cells in immune defense is fundamental in the study of human health and immunology.