Targeting FcαRI on polymorphonuclear cells induces tumor cell killing through autophagy

Neutrophils are the most abundant circulating FcR-expressing WBCs with potent cytotoxic ability. Currently, they are recognized as promising effector cells for Ab-mediated immunotherapy of cancer, because their capacity to kill tumor cells is greatly enhanced by tumor Ag-specific mAbs. The FcαRI represents the most potent FcR on neutrophils for induction of Ab-mediated tumor cell killing. However, the mechanisms of cell death that are induced are poorly understood. Because these mechanisms can be used for modulation of anticancer treatment, we investigated the tumor cell death induced by neutrophil-mediated Ab-dependent killing via FcαRI. Human mammary carcinoma cells were efficiently killed when incubated with human neutrophils and tumor-specific FcαRI bispecific or IgA Abs. Interestingly, we observed characteristics of autophagy such as autophagic structures by electron microscopy and LC3B(+) autophagosomes in different human epithelial carcinoma cells, which resulted in tumor cell death. To a lesser extent, necrotic features, such as cellular membrane breakdown and spillage of intracellular content, were found. By contrast, apoptotic features including fragmented nuclei, Annexin V-positivity, and presence of cleaved caspase-3 were not observed. These findings indicate that neutrophils mainly facilitate autophagy to induce tumor cell death rather than the more commonly recognized apoptotic cell death mechanisms induced by NK cells or cytotoxic T cells. This knowledge not only reveals the type of tumor cell death induced in neutrophil-mediated, Ab-dependent cellular cytotoxicity, but importantly opens up additional perspectives for modulation of anticancer therapy in, for example, apoptosis-resistant tumor cells.     

The sour taste of acids. The hydrogen ion and the undissociated acid as sour agents

In the first of two experiments, the sourness of aqueous solutionsof HCl and of several carboxylic acids was measured by meansof a fitter-paper method. Perceived sourness of the carboxylicacids was positively correlated with the dissociation constantK_al. In contrast to HCl, the H⁺ concentration in carboxylicacids appeared not to be the only factor in eliciting sourness.Decreasing pH by buffering of the carboxylic acids with theirsodium salts did not lower perceived sourness. The rank-orderof the acids, according to the amount of NaOH needed for titration,depends on the pH to which it is titrated. The rank-order ofpH 4.4 reasonably fits the sourness rank-order. In the secondexperiment, adaptation and cross-adaptation of HCl, tartaric-lactic-,and acetic acid were measured. Neither self- nor cross-adaptationwas observed in the case of HCl, whereas with the carboxylicacids self- and mutual cross-adaptation did occur. The presentresults suggest that HCl-sourness and the sourness of carboxylicacids are elicited by different receptor processes.     

Cross-adaptation in taste measured with a filter-paper method

A filter-paper method was applied to self- and cross-adaptationin taste. The original method was modified in order to overcomethree problems: (i) unreliable replacement of the test stimulusafter removal of the adapting stimulus, (ii) incomplete removalof the adapting stimulus liquid, and (iii) migration of stimulusliquid to unadapted surrounding tissue. With NaCl, sucrose anddi-quinine sulfate >70% of complete self-adaptation was retainedafter substituting the adapting stimulus with an identical testpaper. Citric acid behaved differently. Only 45% of the completeadaptation survived the change from adapting to test stimulus.It is speculated that this exception of citric acid is due tospecific physico-chemical properties of acids combined withthe use of the filter-paper method. The experiments show thatthe filter-paper method provides a useful and reliable procedurefor the investigation of cross-adaptation in taste.     

The use of filter paper as stimulus carrier in taste research

Seven types of filter paper were used as a stimulus carrierin a taste experiment. It was shown that the type of filterpaper used has a negligible influence on perceived intensityand on time to complete adaptation. Post hoc grouping into hardenedand soft papers revealed slightly higher subjective intensitiesand longer adaptation times for soft papers.