A predominance of M2b macrophages in mesenteric lymph nodes of mice exposed to whole body 137Cs γ-irradiation (89.32)

Abstract

Abstract In accompanying studies, we have demonstrated that mice exposed to 5 Gy whole body 137Cs γ-irradiation (5 GY-mice) are greatly susceptible to bacterial translocation. M1Mϕ (IL-12+IL-10− Mϕ), host defense effector cells against bacterial translocation, were not demonstrated in mesenteric lymph nodes (MLN) of these mice. M2Mϕ (IL-12−IL-10+ Mϕ) were predominated in MLN of 5 GY-mice. M2Mϕ are inhibitory on Mϕ conversion from resident Mϕ to M1Mϕ. In this study, MLN-M2Mϕ isolated from mice 14 days after 5 Gy γ-irradiation were characterized biophysically. F4/80+ cells (1 x 106 cells/ml) isolated from MLN were cultured with 106 heat-killed Enterococcus faecalis for 48 hrs. Culture fluids harvested were assayed for IL-10, CCL17, CCL1 and CXCL13 by ELISA. Also, cells harvested from the cultures were assayed for mannose receptor and LIGHT mRNA expression by RT-PCR. In the results, CCL1 and IL-10 were detected in the culture fluids of MLN F4/80+ cells isolated from 5 GY-mice. Also, these Mϕ expressed LIGHT mRNA. CCL17 and CXCL13 were not produced and mannose receptor mRNA was not expressed by these Mϕ. An 86% of antigen-stimulated Mϕ conversion from resident Mϕ to M1Mϕ was inhibited by MLN F4/80+ cells isolated from 5 GY-mice. CCL17 and mannose receptor are biomarkers of M2aMϕ, CCL1 and LIGHT are biomarkers of M2bMϕ, and CXCL13 and mannose receptor are biomarkers of M2cMϕ. These results indicate that F4/80+ Mϕ isolated from MLN of 5 GY-mice are M2bMϕ.