Claudin-1, claudin-2 and claudin-11 genes differentially associate with distinct types of anti-inflammatory macrophages in vitro and with parasite- and tumour-elicited macrophages in vivo.

Macrophages altered by various Th2-associated and anti-inflammatory mediators--including IL-4 and IL-13 [inducing alternatively activated macrophages (AAMs)], IL-10 and TGF-ß--were generically termed M2. However, markers that discriminate between AAMs and other M2 remain scarce. We previously described E-cadherin as a marker for AAMs, permitting these macrophages to fuse upon IL-4 stimulation. To identify novel potential contributors to macrophage fusion, we assessed the effect of IL-4 on other adherens and tight junction-associated components. We observed an induction of claudin-1 (Cldn1), Cldn2 and Cldn11 genes by IL-4 in different mouse macrophage populations. Extending our findings to other stimuli revealed Cldn1 as a mainly TGF-ß-induced gene and showed that Cldn11 is predominantly associated with IL-4-induced AAMs. Cldn2 is upregulated by diverse stimuli and is not associated with a specific macrophage activation state in vitro. Interestingly, different claudin genes preferentially associate with M2 from distinct diseases. While Cldn11 is predominantly expressed in AAMs from helminth-infected mice, Cldn1 is the major macrophage claudin during chronic trypanosomiasis and Cldn2 dominates in tumour-associated macrophages. Overall, we identified Cldn1, Cldn2 and Cldn11 as genes that discriminate between diverse types of M2.

Subset characterization of myeloid-derived suppressor cells arising during induction of BM chimerism in mice.

To date, myeloid-derived suppressor cells (MDSC) have been best studied in cancer, where they represent an escape mechanism for immune surveillance. MDSC are now also gaining interest in the context of transplantation. Suppressive CD11b(+) myeloid progenitor cells have been reported to expand endogenously during BM chimerism induction in mice; in particular, in irradiated MHC-matched BM chimeras and in parent-in-F1 BM chimeras. Myeloid cell expansion coincided with a time frame where donor lymphocyte infusion (DLI) therapy-mediated GVL effects without GVHD. Hypothesizing that regulatory myeloid cells may have a role in regulating post-transplant T-cell alloreactivity, we performed a detailed phenotypic and functional characterization of these cells in the parent-in-F1 C57BL/6 → [C57BL/6xDBA2] model. We found that transiently expanding CD11b(+) myeloid progenitor cells comprise the two phenotypically and functionally distinct mononuclear and polymorphonuclear MDSC subsets that were recently described in tumor-bearing mice. Both MDSC subsets suppressed in vitro and in vivo alloreactive T-cell proliferation. Also, both the subsets mediated enhanced in vitro suppression when harvested from chimeras, given a prior in vivo challenge with non-tolerant donor T cells, indicating that allo-activated T cells can activate MDSC in vivo. This study provides the basis to investigate the-potentially beneficial-role of expanding MDSC in influencing the risk of GVHD during chimerism induction.

B7-1, IFN gamma and anti-CTLA-4 co-operate to prevent T-cell tolerization during immunotherapy against a murine T-lymphoma.

We previously reported on a murine T lymphoma cell line, BW-Sp3, with inherent immunogenicity. BW-Sp3 tumors can elicit an anti-tumor CD8(+) CTL response capable of mediating a regression of subcutaneous tumors. However, this immune response is inadequate to eliminate cancer cells completely in a significant percentage of the recipients, resulting in progressing tumors. In this tumor model, tumor progression correlated with a tolerization of tumor-reactive T cells and cellular immunotherapy of tumor bearing animals, with or without B7-mediated costimulation, even increased tumor progression (Raes et al, 1998). In the present study, we investigated whether the co-expression of IFN gamma, together with B7-1, could have beneficial effects on immunotherapy. Although immunotherapy with IFN gamma and B7-1 single transfectants tended to tolerize anti-tumor T-cells and consequently increased tumor growth, the B7-1/IFN gamma double transfectants resulted in a more beneficial outcome. This phenomenon correlated with an increased CTL-inducing potential of the double transfectants. Secondly, we wondered whether CTLA-4 signalling was involved in the down-regulation of the anti-tumor response. Indeed, when immunotherapy was provided along with anti-CTLA-4, the protection by B71/IFN gamma double transfectants was further improved and the tumor-promoting effect of BW-Sp3(B7-1) was compensated for. Our results indicate that B7-1, IFN gamma and the blockade of CTLA-4 cooperate to tilt the balance in favour of tumor elimination, while either factor alone fails to do so or even promotes tumor growth.