Langerhans cells are immature dendritic cells containing large granules called Birbeck granules. On infection of an area of skin, the local Langerhan's cells will take up and process microbial antigens before travelling to the T-cell areas in the cortex of the draining lymph node and maturing to become fully-functional antigen-presenting cells.
Generally, dendritic cells in tissue (such as Langerhan's cells) are active in the capture, uptake and processing of antigens. Once dendritic cells arrive in secondary lymphoid tissue however, they lose these properties while gaining the capacity to interact with naive T-cells.