CD1A and Allergy: However, the expression of group 1 molecules is largely limited to antigen-presenting cells (APCs) and thymocytes, whereas CD1d is additionally expressed by other haematopoietic and epithelial cells.1 In contrast to the aforementioned CD1 molecules, CD1e is involved in lipid processing and loading rather than antigen presentation.4 CD1 molecules have been implicated in a broad range of disorders such as cancer, infections, autoimmune disorders and allergies.5–9