CD169 identifies an anti‐tumour macrophage subpopulation in human hepatocellular carcinoma

Macrophages are a major component of most solid tumours and can exert both anti‐ and pro‐tumourigenic functions. Although the immunosuppressive/pro‐tumour roles of macrophages have been widely examined, significantly less is known about macrophage subpopulations that have potential anti‐tumour properties in humans. In the present study, a population of CD169⁺ macrophages with relatively high expression levels of HLA‐DR and CD86 was identified in human hepatocellular carcinoma tissues. The frequency of CD169‐expressing macrophages within cancer nests was significantly lower than that found in paired non‐tumour areas. In vitro experiments revealed that in the presence of anti‐CD3 stimulation, CD169⁺ macrophages could significantly enhance the proliferation, cytotoxicity, and cytokine production capacity of CD8⁺ T cells in a CD169 molecule‐dependent manner. Autocrine TGF‐β produced by tumour‐stimulated macrophages was involved in the down‐regulation of CD169 expression on these cells. Moreover, the accumulation of CD169⁺ macrophages in tumour tissues was negatively associated with disease progression and predicted favourable survival in hepatocellular carcinoma patients, which was in contrast to the trend observed for total CD68⁺ macrophages. Therefore, CD169 might act as a co‐stimulatory molecule for cytotoxic T‐cell activation, and could define a population of tumour‐infiltrating macrophages with potential anti‐tumour properties in human hepatocellular carcinoma tissues. Copyright © 2016 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.