Neurofibromatosis 1 (NF1) is one of the most common genodermatoses and cutaneous neurofibromas (cNFs) manifest in almost every adult with NF1. The immune microenvironment of cNFs is incompletely known. A total of 60 cNFs from ten patients with NF1 were used for immunolabeling. Tumor T-cells were visualized and counted based on positive reaction for CD3, CD4, CD8 and FoxP3. CD68 and CD163 were used to detect macrophages. The aggregation of cells at the tumor margin was separately assessed for the topmost part of the tumor covered by epidermis. Nine cNFs were analysed by separating the overlying skin and the tumor, and isolating genomic DNA from both tissues. The T cell receptor (TCR) CDR domain was sequenced to compare the T cell profiles of cNFs and the skin. Mass spectrometric analysis of 15 cNFs and the overlying skin was performed to compare the expression of inflammation-related pathways in skin and cNF. Intratumoral T cells were detected in all samples, and the T-cell population of cNFs was clearly CD4-dominant. Most samples displayed aggregation of CD3 positive cells at the tumor margin in the area underlying epidermis.The density of CD68 positive macrophages was higher in cNFs from older patients (P=0.019). CD163 positive cells suggestive of M2 macrophages were abundant in cNFs. TCR sequencing showed that the T-cell populations of the tumor and overlying skin were clearly distinct. The number of productive TCR rearrangements observed in cNFs (mean 1,200) was significantly lower compared to skin (mean 5,190; P<0.001). The mass spectrometry data showed that many processes related to T cells were downregulated in cNFs. This study gives an overview of tumor immune microenvironment of cNFs and paves the way for detailed studies to elucidate potential therapeutic targets for the treatment or for the prevention of the growth of cNFs.

ESDR289 - Immune cell population of cutaneous neurofibromas

The scientific meeting of the European Society for Dermatological Research (ESDR) is held yearly, usually in September. With an international attendance of more than 1000 skin scientists from around the globe, the four-day event includes short oral presentations from peer-reviewed abstracts, keynote lectures from international experts, sponsored symposia, satellite programs, educational events as well as an important focus on posters, networking and building collaborations amongst scientists. For more information about this year’s meeting visit our website.