What structure is primarily involved in the body's immune response?

Langerhans cells play a crucial role in the body’s immune response as they are specialized dendritic cells found in the skin. They are important for recognizing and processing antigens—substances that can induce an immune response—in the epidermis. Once they capture these antigens, Langerhans cells migrate to lymph nodes where they present the antigens to T cells, thereby initiating a specific immune response. This process is vital for the body’s defense mechanism against pathogens, making Langerhans cells essential for skin immunity.

The thyroid gland primarily regulates metabolism and is not directly involved in the immune response. The adrenal gland produces hormones like cortisol and adrenaline that can influence immune function but is not the primary structure responsible for carrying out immune reactions. The pancreas is crucial for digestion and regulating blood sugar levels through insulin production, but it does not play a direct role in the body's primary immune response.