GITR (glucocorticoid‐induced TNFR family related gene) is a member of the TNFR superfamily (TNFRSF) that is expressed in different cell types, including T lymphocytes. Because of a high homology in its cytoplasmic region with other known costimulatory members of the TNFRSF, we investigated whether GITR played a costimulatory role in T lymphocyte subpopulations. Our results show that the proliferation response of CD8⁺ and CD4⁺ peripheral T cell subpopulations was potentiated when a GITR costimulus was added to an anti‐CD3 stimulus. Furthermore, expression of the main activation‐induced receptor (IL‐2Rα) and production of IL‐2 and IFN‐γ were increased more with a GITR costimulus than with anti‐CD3 alone. GITR stimulation also enhanced anti‐CD3‐induced ERK phosphorylation, suggesting that GITR is involved in MAPK‐pathway activation. Interestingly, CD4⁺CD25⁺ regulatory T cell (Treg cell) proliferation was triggered by the GITR costimulus; Treg cell proliferation was paralleled by the loss of the anergic phenotype and suppressor activity. Nevertheless, unstimulated GITR^–/– CD4⁺CD25⁺ and GITR^+/+ CD4⁺CD25⁺ cells were equally able to exert suppressor activity on CD4⁺CD25^– responder cells. These results indicate a novel function for GITR as costimulatory molecule of T cell subsets.

Antibody Fc-driven engagement of macrophages is critical for evoking cellular activation and effector functions and influencing tumour-associated macrophage (TAM) recruitment. We previously reported that IgE class antibodies promote restriction of cancer growth in rodent models associated with significant TAM infiltration. However, the human macrophage-associated IgE-Fc Receptor (FcεR) axis remains unexplored. We investigated the effects of anti-tumour IgE stimulation on human macrophage activation. Human blood monocyte-differentiated quiescent (M0), classically-(M1) and alternatively-(M2) activated macrophages were crosslinked with IgE and polyclonal antibodies to mimic immune complex formation. We examined surface marker expression, cytokine secretion, protein kinase phosphorylation and gene expression in IgE-stimulated macrophages and IgE antibody-dependent macrophage-mediated cytotoxicity (ADCC) against tumour cells. A proportion (40%) of M2 and (<20%) M0 and M1 macrophages expressed the high-affinity IgE receptor FcεRI. IgE crosslinking triggered upregulation of co-stimulatory CD80, increased TNFα, IFNγ, IL-1β, IL-12, IL-10, IL-13, CXCL9, CXCL11 and RANTES secretion by M0 and M2 and additionally enhanced MCP-1 by M2 macrophages. IgE-stimulated M1 macrophages retained secretion of pro-inflammatory cytokines. IgE crosslinking enhanced the FcεRI-dependent signalling pathway, including phosphorylation of the Lyn kinase, ERK1/2 and p38 in M2 macrophages and upregulated Lyn gene expression by M1 and M2 macrophages. Anti-tumour IgE engendered ADCC of cancer cells by all macrophage subsets. IgE can engage and re-educate alternatively-activated macrophages towards pro-inflammatory phenotypes and prime all subsets to mediate anti-tumour functions. This points to IgE-mediated cascades with potential to activate immune stroma and may be significant in the clinical development of strategies targeting tumour-resident macrophages.

Th2 immunity and allergic immune surveillance play critical roles in host responses to pathogens, parasites and allergens. Numerous studies have reported significant links between Th2 responses and cancer, including insights into the functions of IgE antibodies and associated effector cells in both antitumour immune surveillance and therapy. The interdisciplinary field of AllergoOncology was given Task Force status by the European Academy of Allergy and Clinical Immunology in 2014. Affiliated expert groups focus on the interface between allergic responses and cancer, applied to immune surveillance, immunomodulation and the functions of IgE‐mediated immune responses against cancer, to derive novel insights into more effective treatments. Coincident with rapid expansion in clinical application of cancer immunotherapies, here we review the current state‐of‐the‐art and future translational opportunities, as well as challenges in this relatively new field. Recent developments include improved understanding of Th2 antibodies, intratumoral innate allergy effector cells and mediators, IgE‐mediated tumour antigen cross‐presentation by dendritic cells, as well as immunotherapeutic strategies such as vaccines and recombinant antibodies, and finally, the management of allergy in daily clinical oncology. Shedding light on the crosstalk between allergic response and cancer is paving the way for new avenues of treatment.

CD28 is well characterized as a costimulatory molecule in T cell activation. Recent evidences indicate that TNFR superfamily members, including glucocorticoid-induced TNFR-related protein (GITR), act as costimulatory molecules. In this study, the relationship between GITR and CD28 has been investigated in murine CD8⁺ T cells. When suboptimal doses of anti-CD3 Ab were used, the absence of GITR lowered CD28-induced activation in these cells whereas the lack of CD28 did not affect the response of CD8⁺ T cells to GITR costimulus. In fact, costimulation of CD28 in anti-CD3-activated GITR^−/− CD8⁺ T cells resulted in an impaired increase of proliferation, impaired protection from apoptosis, and an impaired rise of activation molecules such as IL-2R, IL-2, and IFN-γ. Most notably, CD28-costimulated GITR^−/− CD8⁺ T cells revealed lower NF-κB activation. As a consequence, up-regulation of Bcl-x_L, one of the major target proteins of CD28-dependent NF-κB activation, was defective in costimulated GITR^−/− CD8⁺ T cells. What contributed to the response to CD28 ligation in CD8⁺ T cells was the early up-regulation of GITR ligand on the same cells, the effect of which was blocked by the addition of a recombinant GITR-Fc protein. Our results indicate that GITR influences CD8⁺ T cell response to CD28 costimulation, lowering the threshold of CD8⁺ T cell activation.

Background: Macrophages can be converted in vitro into immunoregulatory M2b macrophages in the presence of immune complexes ( IC s), but the role of the specific subclasses IgG1 or IgG4 in this phenotypic and functional change is not known. Objective: We aimed to refine the original method by applying precisely defined IC s of the subclasses IgG4 or IgG1 constructed by two independent methods. Methods: Monocyte‐derived macrophages ( MDM s) were treated with M‐ CSF , followed by IL ‐4/ IL ‐13 to induce the M2a allergic phenotype. To mimic unspecific or allergen‐specific IC s, plates were coated with myeloma IgG1 or IgG4, or with grass pollen allergen Phl p 5 followed by recombinant human Phl p 5‐specific IgG1 or IgG4. M2a polarized macrophages were then added, cultured, and examined for cellular markers and cytokines by flow cytometry, ELISA , and rt PCR . Alternatively, immune complexes with IgG1 or IgG4 were formed using protein L. Results: IgG4 IC s down regulated CD 163 and CD 206 on M2a cells, and significantly increased IL ‐10, IL ‐6, TNF α, and CCL 1 secretion, indicating a shift to an M2b‐like phenotype. Treatment with IgG4 IC s resulted in expression of Fcγ RII and down modulation of Fcγ RII compared with IgG1 treated cells ( P = 0.0335) or untreated cells ( P < 0.00001). Conclusion: Immune complexes with subclasses IgG1 and IgG4 can in vitro be generated by plate absorption, and in fluid form by protein L. Cross‐linking of Fcγ RII b by the IgG4 subclass redirects pro‐allergic M2a macrophages to an M2b‐like immunosuppressive phenotype. This suggests an interplay of macrophages with IgG4 in immune tolerance, likely relevant in allergen immunotherapy.