Dermal dendrocytes FXIIIa+ are essential antigen-presenting cells in indeterminate leprosy.

Indeterminate leprosy (IL) is the early phase of Hansen disease and reword (APCs). Langerhans cells and dermal dendrocytes FXIIIa positive (DDFXIIIa) are the major APCs in the skin and can be identified by the expression of CD1a and FXIIIa, respectively, by immunohistochemical techniques. Plasmacytoid dendritic cells (PDCs) are another type of dermal dendrocytes with a questionable antigen-presenting function and can be highlighted by anti-CD123 expression. To our knowledge, there are no studies evaluating DDFXIIIa and PDC in IL. The purpose was to investigate the involvement of these cells in the pathogenesis of IL. The authors performed a retrospective study on 18 cases of IL (10 confirmed and 8 suspected) to investigate expression of FXIIIa, CD1a, and CD123. The results were compared with normal skin (for CD1a and FXIIIa only). A higher amount of FXIIIa-positive cells (P , 0.05) in confirmed and suspected IL cases was noted when comparing with normal skin. However, CD1a showed no quantitative differences in the epidermis of IL lesions when comparing with normal skin and CD123 expression was negligible. Based on these findings, the authors postulate that Langerhans cells and PDCs do not have a major role in IL and that DDFXIIIa may be the main APCs in IL. Further study is required to establish this.