IL-2/CD40-activated macrophages rescue age and tumor-induced T cell dysfunction in elderly mice

Abstract

The role of macrophages and their interactions with T cells during aging is not well understood. We determined if activating elderly-derived macrophages could rescue age-related and tumor-induced T cell dysfunction. Healthy elderly (18-24 months) Balb/c contained significantly more splenic IL-10-secreting M2-macrophages and myeloid-derived suppressor cells than young (6-8 weeks) mice. Exposure to syngeneic mesothelioma or lung carcinoma-conditioned media polarized peritoneal macrophages into suppressive M2-macrophages regardless of age. Tumor-exposed, elderly, but not young-derived, macrophages produced high levels of IL-4 and could not induce T cell IFN-γ production. We attempted to rescue tumor-exposed macrophages with LPS/IFN-γ (M1 stimulus) or IL-2/agonist anti-CD40 antibody. Tumor-exposed, M1-stimulated macrophages retained high CD40 expression, yet TNF-α and IFN-γ production were diminished relative to non-tumor-exposed, M1-stimulated controls. These macrophages induced young and elderly-derived T cell proliferation however, T cells did not secrete IFN-γ. In contrast, tumor-exposed, IL-2/CD40-stimulated macrophages rescued elderly-derived T cell IFN-γ production, suggesting that IL-2/CD40-activated macrophages could rescue T cell immunity in aging hosts.

Macrophage Depletion in Elderly Mice Improves Response to Tumor Immunotherapy, Increases Anti-tumor T Cell Activity and Reduces Treatment-Induced Cachexia

“…We have previously shown that intra-tumoral IL-2 combined with anti-CD40 antibody leads to AE17 mesothelioma tumor regression in young mice; this was associated with increased CTL activity ( Jackaman et al, 2008 , 2016 ). Furthermore, in vitro studies showed that elderly derived IL-2/anti-CD40-activated macrophages could restore age- and tumor-related T cell function ( Jackaman et al, 2013 , 2014 ). Therefore, we next examined whether IL-2/anti-CD40 was effective in young vs. elderly AE17 tumor-bearing mice and whether macrophages contributed to the efficacy of IL-2/anti-CD40 immunotherapy.…”

“…This response included the generation of anti-tumor CTLs and polarization of macrophages into a pro-inflammatory phenotype within DLNs in young mice in vivo ( Jackaman et al, 2016 ). Similarly, we have shown that IL-2/anti-CD40-activated macrophages can rescue age- and tumor-induced T cell function in vitro ( Jackaman et al, 2013 , 2014 ). However, it is likely that the inflammaging microenvironment plays a pivotal role in age-related macrophage dysfunction ( Oishi and Manabe, 2016 ) and further in vivo studies are required.…”

“…However, in separate studies BM-derived macrophages from elderly female C57BL/6J mice (aged 16–22 months) exhibited increased TNF-α and IL-6 production in response to LPS ( Bouchlaka et al, 2013 ; Thevaranjan et al, 2017 ). Similarly, elderly derived female Balb/c (aged 17–18 months) and C57BL/6J peritoneal macrophages (aged 24–28 months) displayed hypersensitivity to anti-inflammatory IL-4 stimuli with increased production of anti-inflammatory IL-10 and TGF-β ( Jackaman et al, 2013 , 2014 ). In vivo murine studies have also described macrophages from the eye, muscles, lymph nodes, spleen and bone marrow expressing increased IL-10 during aging ( Wang et al, 1995 , 2015 ; Kelly et al, 2007 ; Jackaman et al, 2013 ).…”

Murine mesothelioma induces locally-proliferating IL-10+TNF-α+CD206−CX3CR1+M3 macrophages that can be selectively depleted by chemotherapy or immunotherapy

“…26,27 CFSElabeled splenocytes were incubated for 2-4 h (37x C, 5% CO 2 ) to remove adherent macrophages and DCs and collect nonadherent cells (consisting of 40% T cells). Splenocytes were labeled with carboxyfluorescein diacetate succinimidyl ester (CFSE; Invitrogen) a fluorescent dye that binds permanently to cell membranes.…”

“…3 Systemic injection of IL-2/CD40 was unacceptably toxic, even in young adult mice, and significantly less effective than intra-tumoral administration. 26,27 Others have shown that targeting and depleting tumor-associated macrophages inhibits mesothelioma tumor development. 3 The role of macrophages was not examined in those studies.…”