Using Cytometry for Investigation of Purinergic Signaling in Tumor-Associated Macrophages

Tumor-associated macrophages are widely recognized for their importance in guiding pro-tumoral or antitumoral responses. Mediating inflammation or immunosuppression, these cells support many key events in cancer progression: cell growth, chemotaxis, invasiveness, angiogenesis and cell death. The communication between cells in the tumor microenvironment strongly relies on the secretion and recognition of several molecules, including damage-associated molecular patterns (DAMPs), such as adenosine triphosphate (ATP). Extracellular ATP (eATP) and its degradation products act as signaling molecules and have extensively described roles in immune response and inflammation, as well as in cancer biology. These multiple functions highlight the purinergic system as a promising target to investigate the interplay between macrophages and cancer cells. Here, we reviewed purinergic signaling pathways connecting cancer cells and macrophages, a yet poorly investigated field. Finally, we present a new tool for the characterization of macrophage phenotype within the tumor. Image cytometry emerges as a cutting-edge tool, capable of providing a broad set of information on cell morphology, expression of specific markers, and its cellular or subcellular localization, preserving cell-cell interactions within the tumor section and providing high statistical strength in small-sized experiments. Thus, image cytometry allows deeper investigation of tumor heterogeneity and interactions between these cells. © 2020 International Society for Advancement of Cytometry.

The capsular polysaccharides of Cryptococcus neoformans activate normal CD4(+) T cells in a dominant Th2 pattern

Capsular components of Cryptococcus neoformans induce several deleterious effects on T cells. However, it is unknown how the capsular components act on these lymphocytes. The present study characterized cellular and molecular events involved in immunoregulation of splenic CD4(+) T cells by C. neoformans capsular polysaccharides (CPSs). The results showed that CPSs induce proliferation of normal splenic CD4(+) T cells, but not of normal CD8(+) T or B lymphocytes. Such proliferation depended on physical contact between CPSs and viable splenic adherent cells (SAC) and CD40 ligand-induced intracellular signal transduction. The absence of lymphoproliferation after fixation of SAC with paraformaldehyde has discarded the hypothesis of a superantigen-like activation. The evaluation of a cytokine pattern produced by the responding CD4(+) T lymphocytes revealed that CPSs induce a dominant Th2 pattern, with high levels of IL-4 and IL-10 production and undetectable inflammatory cytokines, such as TNF-alpha and IFN-gamma. Blockade of CD40 ligand by relevant mAb down-regulated the CPS-induced anti-inflammatory cytokine production and abolished the enhancement of fungus growth in cocultures of SAC and CD4(+) T lymphocytes. Our findings suggest that CPSs induce proliferation and differentiation of normal CD4(+) T cells into a Th2 phenotype, which could favor parasite growth and thus important deleterious effects to the host.

Glycoinositolphospholipids purified from Trypanosoma cruzi stimulate Ig production in vitro

We have investigated the effects of glycoinositolphospholipid (GIPL) purified from Trypanosoma cruzi on murine B cell activation. The GIPL neither stimulated any proliferative response by itself, nor affected the blastogenesis induced by surface IgD cross-linking or LPS. On the other hand, the GIPL significantly stimulated both low and high density B cells to secrete IgM in vitro. The GIPL induced B cells to produce IgM when added in the presence of either the surface Ig cross-linker, anti-delta-dextran, or a combination of IL-4 and IL-5. The T. cruzi-derived GIPL also stimulated Ig class switch to IgG1 in cultures stimulated with GIPL, IL-4, and IL-5. The IgG1 secretion was comparable to that induced by LPS plus IL-4. Production of IgG3 was also detected and the GIPL also potentiated the IgG3 production induced by LPS. The stimulatory effect of the T. cruzi-derived GIPL was mediated mainly by its oligosaccharide moiety. This isolated fraction induced a potent IgM secretory response, compared with a much lower response induced by the isolated GIPL ceramide. Taken together, our data suggest that the stimulatory effect of the T. cruzi-derived GIPL on B cell activation could play a role on the conspicuous Ig production observed during infection of the host with T. cruzi.

Glycoinositolphospholipids purified from Trypanosoma cruzi stimulate Ig production in vitro

We have investigated the effects of glycoinositolphospholipid (GIPL) purified from Trypanosoma cruzi on murine B cell activation. The GIPL neither stimulated any proliferative response by itself, nor affected the blastogenesis induced by surface IgD cross-linking or LPS. On the other hand, the GIPL significantly stimulated both low and high density B cells to secrete IgM in vitro. The GIPL induced B cells to produce IgM when added in the presence of either the surface Ig cross-linker, anti-delta-dextran, or a combination of IL-4 and IL-5. The T. cruzi-derived GIPL also stimulated Ig class switch to IgG1 in cultures stimulated with GIPL, IL-4, and IL-5. The IgG1 secretion was comparable to that induced by LPS plus IL-4. Production of IgG3 was also detected and the GIPL also potentiated the IgG3 production induced by LPS. The stimulatory effect of the T. cruzi-derived GIPL was mediated mainly by its oligosaccharide moiety. This isolated fraction induced a potent IgM secretory response, compared with a much lower response induced by the isolated GIPL ceramide. Taken together, our data suggest that the stimulatory effect of the T. cruzi-derived GIPL on B cell activation could play a role on the conspicuous Ig production observed during infection of the host with T. cruzi.

Rat paw edema and leukocyte immigration induced by plant lectins

Lectins from Dioclea grandiflora (DG) and Canavalia brasiliensis (CB) were compared with Concanavalin A (ConA) for their ability to induce paw edema and peritoneal cell immigration in rats. ConA caused a slight edema with a peak at 1 h after injection, while DG or CB induced a pronounced and long-lasting edema that reached a maximum at about 6 h. Different antiinflammatory drugs partially inhibited the edema. alpha-D-glucose (GLU) partially blocked the edema caused by ConA and markedly inhibited that due to CB, but had no effect on the edema induced by DG. alpha-Methyl mannoside (alpha-MM) blocked the edema caused by DG and ConA, but did not affect that caused by CB. At doses much lower than those used to induce paw edema, the lectins promoted an intense accumulation of neutrophil and mononuclear cells in the rat peritoneal cavity. CB and DG were more potent than ConA, which also presented a different profile of cell immigration. GLU significantly inhibited leukocyte accumulation caused by all lectins. alpha-MM impaired ConA- and DG-induced cell immigration, but only partially inhibited CB. Thus, despite their physicochemical similarities with ConA, DG and CB have more powerful pro-inflammatory effects. This difference seems to be related to their sugar-binding properties. However, while ConA- and DG-induced effects were inhibited more by alpha-MM than by GLU, CB-induced effects were inhibited more by glucose.