What is the primary function of the immune system?

The primary function of the immune system is to defend against pathogens, which include bacteria, viruses, parasites, and fungi that can cause disease. The immune system is a complex network of cells, tissues, and organs that work together to identify and eliminate these harmful invaders. Key components of the immune system include white blood cells, antibodies, and the lymphatic system, all of which play crucial roles in recognizing and responding to threats.

When a pathogen enters the body, the immune system activates an array of responses, such as inflammation and the activation of specialized immune cells that can target and destroy the pathogens. This protective mechanism allows the body to maintain health and resistance to infections. The ability of the immune system to remember past infections (through memory cells) also contributes to long-lasting immunity.

In contrast, the other functions mentioned—regulating body temperature, transporting nutrients, and facilitating cellular respiration—are carried out by different systems in the body. The circulatory system is responsible for transporting nutrients, the integumentary system (including skin) plays a role in temperature regulation, and cellular respiration is primarily a function of cellular metabolism within the mitochondria of cells. These systems operate independently from the immune system and are not its primary role.