CD1a and langerin: acting as more than Langerhans cell markers.

Langerhans cells (LCs) represent a unique DC subset populating the outermost body surface, i.e., the epidermis. Although CD1a and langerin (CD207) are used as specific markers to distinguish LCs from other DC subsets, their immunological functions have remained mostly unknown. A new paper (see the related article beginning on page 701) demonstrates that LCs utilize these markers to induce cellular immune responses to Mycobacterium leprae: CD1a mediates the presentation of nonpeptide antigens to T cells, while langerin facilitates uptake of microbial fragments and perhaps their delivery to a specialized subcellular compartment.