Methods for identifying sentinel lymph nodes (SNs) and their clinical significance have been established. Recent advances in molecular immunology have enabled the analysis of precise immune responses. The objective of the current study was to clarify the dendritic cell (DC) maturation, T‐helper type 1 (Th‐1) and Th‐2 responses, and regulatory T‐cell responses of SNs in patients with breast carcinoma.

SNs and non‐SNs were identified by radioguided and blue dye‐guided methods in 70 consecutive patients with clinically lymph node negative (N0) breast carcinoma. Lymphocytes were collected from SNs and non‐SNs and were subjected to flow cytometric analysis (FCM) using antibodies of CD83‐fluorescein isothiocyanate (FITC), CD80‐phycoerythrin (PE), CD86‐PE, CD40‐PE, human leukemic D‐related antigen (HLA‐DR)‐FITC, CD4‐FITC, and CD25‐PE. Total RNA was extracted from SNs and non‐SNs, and the expression of CD83, interleukin 12p40 (IL‐12p40), interferon γ (IFN‐γ), IL‐4, IL‐10, and Foxp3 was evaluated by using quantitative real‐time reverse transcriptase‐polymerase chain reaction (RT‐PCR) analysis. The immunologic status of SNs was analyzed further with regard to micrometastases, which were identified as negative microscopically but positive according to an RT‐PCR analysis that was specific for mammaglobin.

SNs were detectable in 70 of 71 consecutive patients (98.6%) with clinically N0 breast carcinoma. Fourteen of 70 patients (20.0%) had positive metastasis in SNs. When SNs were compared with non‐SNs in 56 metastasis‐negative patients, FCM revealed that HLA‐DR‐positive, CD80‐positive, CD86‐positive, and CD40‐positive cell populations were decreased significantly in SNs. RT‐PCR analysis demonstrated that, among 44 patients with metastasis‐negative SNs, the expression levels of CD83 and IFN‐γ mRNA were significantly lower in SNs compared with non‐SNs. Immunologic parameters also were compared between 44 metastasis‐negative SNs and 14 metastasis‐positive SNs. The metastasis‐positive SNs demonstrated significantly higher expression of CD83, IL‐12p40, IFN‐γ, IL‐10, and Foxp3 mRNA than the metastasis‐negative SNs. Correction of micrometastasis detected by mammaglobin enhanced these differences consistently.

In patients with breast carcinoma, cellular immune responses, from DC maturation to Th‐1 responses, appeared to be less active in SNs compared with non‐SNs before metastasis developed. Once metastasis was established in SNs, DC maturation was triggered and was followed by the up‐regulation of Th‐1 responses, which may reflect antigen‐specific immune responses in SNs. Unlike DC maturation and Th‐1 responses after metastasis in SNs, up‐regulation of Th‐2 and regulatory T‐cell responses developed in parallel. Cancer 2006. © 2006 American Cancer Society.