Dendritic cell function in sentinel nodes.

Intraoperative lymphatic mapping and sentinel lymphadenectomy has become an increasingly popular technique for staging the regional lymph nodes in early-stage melanoma. This operative technique allows for detailed pathologic analysis of the first (or sentinel) lymph node in direct connection with the primary tumor, and provides a unique opportunity for assessing potential immunologic interactions between the primary tumor and regional lymph node basin. We performed lymphatic mapping and sentinel lymphadenectomy on 25 patients with early-stage melanoma and resected an additional nonsentinel node in each case. Sentinel and nonsentinel nodes were evaluated by routine pathologic analysis. A portion of each node was processed for expression of the dendritic markers of activation CD80, CD86, and CD40, and their corresponding T-cell receptors CTLA-4 and CD28. Of 25 patients undergoing lymphatic mapping and sentinel lymphadenectomy, 20 (80%) had matched sentinel and nonsentinel nodes. A total of 26 matched lymph node sets were obtained: three pairs from one patient and two from an additional two patients. Reverse transcription polymerase chain reaction analyses of corresponding sections of the sentinel and nonsentinel nodes demonstrated a marked reduction in semiquantitative expression of CD80 (77%), CD86 (77%), and CD40 (85%), as well as CTLA-4 (88%) and CD28 (85%) in sentinel as compared to nonsentinel nodes. The diminished expression of the dendritic cell markers appeared to be unrelated to the B-cell (CD20) and T-cell (CD2) expression. Lymphatic mapping and sentinel lymphadenectomy allows for detailed pathologic and molecular characterization of sentinel nodes. Our results suggest a quantitative reduction in dendritic cell markers in sentinel as compared to nonsentinel nodes, which may be important in the immunologic interaction between the primary site and regional lymph node basin and may also serve as useful criteria for identifying sentinel nodes.