What acts as the skin's first line of defense against pathogens?

The skin's first line of defense against pathogens is primarily attributed to Langerhans cells. These specialized immune cells reside within the epidermis and play a crucial role in the skin's immune response. They are capable of detecting and capturing foreign invaders, such as bacteria and viruses, which allows them to initiate an immune response. Langerhans cells function by processing and presenting antigens to T cells, thereby acting as a critical component in the skin's defense against infections.

Keratinocytes, while abundant in the epidermis and important for forming a protective barrier, primarily serve to prevent moisture loss and provide structural support. Melanocytes are involved in pigmentation and protection against ultraviolet radiation but do not play a direct role in defending against pathogens. Fibroblasts are key in the dermis, contributing to the formation of connective tissue and wound healing but are not directly involved in immune surveillance like Langerhans cells. This specialization in pathogen detection and response underscores the role of Langerhans cells as the first line of defense in the skin's immune system.