Abstract Besides being a preferential site of early metastasis, the sentinel lymph node (SLN) is also a privileged site of T-cell priming, and may thus be an appropriate target for investigating cell types involved in antitumor immune reactions. We determined the prevalence of OX40+ activated T lymphocytes, FOXP3+ regulatory T cells, DC-LAMP+ mature dendritic cells (DCs) and CD123+ plasmacytoid DCs by immunohistochemistry in 100 SLNs from 60 melanoma patients. Density values of each cell type in SLNs were compared to those in non-sentinel nodes obtained from block dissections (n=37), and analyzed with regard to associations with clinicopathological parameters and disease outcome. Sentinel nodes showed elevated amount of all cell types studied in comparison to non-sentinel nodes. Metastatic SLNs had higher density of OX40+ lymphocytes compared to tumor-negative nodes, while no significant difference was observed in the case of the other cell types studied. Within the sentinel-positive group, FOXP3+ cell density was higher in patients showing disease progression and >5 years survival than in those without progression and <5 years survival, respectively, or in sentinel-negative cases. High amount of FOXP3+ cells in SLNs was associated with shorter progression-free (P=0.0203) and overall survival (P=0.0238), while no significant correlation was found in the case of the other immune cell types. In multivariate analysis, SLN status, ulceration, Breslow index and patient gender, but not the density values of the immune cell types, proved significant independent predictors of survival. Taken together, our results are compatible with the hypothesis of functional competence of sentinel lymph nodes based on the prevalence of the studied immune cells. The density of FOXP3+ lymphocytes showed association with progression and survival, but none of the immune markers emerged as independent prognostic factor. These results, together with our previous findings on the prognostic value of activated T cells and mature DCs infiltrating primary melanomas, suggest that immune cells residing in the primary tumor, rather than those in sentinel lymph nodes, may be crucial in the development of antitumor immune response reflected in influencing the outcome of the disease. This work was supported by the National Scientific Research Fund OTKA 72836. *The first two authors contributed equally to the work. Citation Format: Anita Mohos, Timea Sebestyen, Gabriella Liszkay, Vanda Plotar, Szabolcs Horvath, Istvan Gaudi, Andrea Ladanyi. Immune cell profile of sentinel lymph nodes in melanoma patients . [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 453. doi:10.1158/1538-7445.AM2013-453