CD 169‐positive macrophages in regional lymph nodes are associated with a favorable prognosis in patients with colorectal carcinoma

CD 169 (sialoadhesin) is a sialic acid receptor that is expressed on specific macrophages such as lymph node sinus macrophages. Animal studies have suggested that CD 169 + macrophages have a pro‐inflammatory property, however, the role of these cells in human diseases has not been clarified. In our in vitro experiments with human macrophages, pro‐inflammatory cytokines, such as type 1 interferon, induced strong expression of CD 169, suggesting that CD 169 might be a specific marker of inflammatory macrophages. To examine the role of CD 169 in antitumor immunity, we examined the expression of CD 169 in regional lymph nodes ( RLN s) and its association with overall survival in colorectal carcinoma ( CRC ). In a clinicopathological analysis on 83 CRC patients, paraffin‐embedded specimens were evaluated for CD 169 expression of RLN macrophages by immunohistochemistry. We found, for the first time, a high density of CD 169 + macrophages was significantly associated with longer overall survival; multivariate analysis showed that the ratio of CD 169 + cells to CD 68 + cells was an independent prognostic factor. The majority of CD 169 + macrophages were in direct contact with CD 8 + T cells expressing CD 43, a major ligand of CD 169. We also found that the density of CD 169 + macrophages had a positive correlation with the number of CD 8 + cytotoxic T cells infiltrating tumor tissues. These data suggest that CD 169 + macrophages in RLN s promote CD 8 + T‐cell‐mediated antitumor immunity and are associated with a better prognosis for CRC patients. CD 169 + macrophages in RLN s could be a useful marker for assessing clinical prognosis and monitoring antitumor immunity in patients with CRC .