Characterization of peritoneal leukemia-associated macrophages in Notch1-induced mouse T cell acute lymphoblastic leukemia.

Macrophages, which have remarkable plasticity, are indispensable cellular components and play essential roles in both innate and adaptive immune responses. Peritoneal macrophages show unique gene expression profile and peritoneal cavity is also involved in leukemia. However, the characteristics of peritoneal leukemia-associated macrophages (Per LAMs) have not been established. Here we studied the phenotype of Per LAMs, their subpopulations in Notch1-induced acute lymphoblastic leukemia mice and compared with LAMs from BM or spleen in the same model. Peritoneal macrophages and Per LAMs simultaneously expressed high level iNOS and Arg1, which was not commonly observed in macrophages from different origins. Furthermore, LAMs from peritoneal, BM and spleen expressed lower level CSF-1, TGF-β1 and VEGF-A than tumor-associated macrophages (TAMs). Moreover, diverse responses in the expression of some phenotype-associated genes to leukemia microenvironments were detected among those LAMs. In addition, Per LAMs can be sub-divided into CD206+ and CD206- sub-populations, which expressed both M1- and M2-associated genes. These results revealed the unique phenotype of Per macrophages and Per LAMs and contributed to better understanding of macrophage plasticity and their pathological roles in leukemia.