Which cells in the epidermis act as antigen-presenting cells and express CD1a?

Which cells in the epidermis act as antigen-presenting cells and express CD1a?

• A. Merkel cells
• B. Langerhans cells (dendritic cells)
• C. Melanocytes
• D. Keratinocytes

Answer: (B)

Antigen presentation in the epidermis is carried out by Langerhans cells, which are dendritic cells that express CD1a. These cells reside in the epidermis (especially the stratum spinosum), capture antigens that enter the skin, and migrate to regional lymph nodes to present processed antigens to T cells. They use MHC class II to present peptide antigens and CD1a to present lipid-based antigens, making them the professional antigen-presenting population in the epidermis. Distinguishing features include Birbeck granules on electron microscopy and their role in initiating T-cell responses after skin exposure. Merkel cells are mechanoreceptors and do not function as APCs; melanocytes produce pigment and are not antigen presenters; keratinocytes are the main epidermal cells but are not CD1a-expressing professional APCs.

Antigen presentation in the epidermis is carried out by Langerhans cells, which are dendritic cells that express CD1a. These cells reside in the epidermis (especially the stratum spinosum), capture antigens that enter the skin, and migrate to regional lymph nodes to present processed antigens to T cells. They use MHC class II to present peptide antigens and CD1a to present lipid-based antigens, making them the professional antigen-presenting population in the epidermis. Distinguishing features include Birbeck granules on electron microscopy and their role in initiating T-cell responses after skin exposure.

Merkel cells are mechanoreceptors and do not function as APCs; melanocytes produce pigment and are not antigen presenters; keratinocytes are the main epidermal cells but are not CD1a-expressing professional APCs.