Final answer:
The stratum spinosum layer of the epidermis is characterized by keratinocytes connected by desmosomes and the presence of Langerhans cells that help fight infection.
Step-by-step explanation:
The skin layer characterized by the presence of cells that fight infection and keratinocytes that are joined by desmosomes is the stratum spinosum layer of the epidermis.
The stratum spinosum is superficial to the stratum basale and plays a vital role in skin health. Desmosomes hold the keratinocytes together, providing structural integrity to the skin. In addition to keratinocytes, this layer is also enriched with Langerhans cells which are part of the immune response, fighting pathogens that enter through the skin. The epidermis itself is a multilayered epithelial structure where the continual process of keratinization occurs. The production of keratin in keratinocytes provides an essential waterproof barrier and strength to the skin.
The skin layer characterized by the presence of cells that fight infection and keratinocytes joined by desmosomes is the stratum spinosum layer of the epidermis. This layer is located superficial to the stratum basale and is responsible for providing a barrier against pathogens and foreign particles.