Alkaline fixation-resistant acid phosphatases in human tissues: histochemical evidence for a new type of acid phosphatase in endothelial, endometrial and neuronal sites

Predicting cytotoxic T-cell age from multivariate analysis of static and dynamic biomarkers

Adoptive T-cell transfer therapy relies upon in vitro expansion of autologous cytotoxic T cells that are capable of tumor recognition. The success of this cell-based therapy depends on the specificity and responsiveness of the T cell clones before transfer. During ex vivo expansion, CD8+ T cells present signs of replicative senescence and loss of function. The transfer of nonresponsive senescent T cells is a major bottleneck for the success of adoptive T-cell transfer therapy. Quantitative methods for assessing cellular age and responsiveness will facilitate the development of appropriate cell expansion and selection protocols. Although several biomarkers of lymphocyte senescence have been identified, these proteins in isolation are not sufficient to determine the age-dependent responsiveness of T cells. We have developed a multivariate model capable of extracting combinations of markers that are the most informative to predict cellular age. To acquire signaling information with high temporal resolution, we designed a microfluidic chip enabling parallel lysis and fixation of stimulated cell samples on-chip. The acquisition of 25 static biomarkers and 48 dynamic signaling measurements at different days in culture, integrating single-cell and population based information, allowed the multivariate regression model to accurately predict CD8+ T-cell age. From surface marker expression and early phosphorylation events following T-cell receptor stimulation, the model successfully predicts days in culture and number of population doublings with R2=0.91 and 0.98, respectively. Furthermore, we found that impairment of early signaling events following T cell receptor stimulation because of long term culture allows prediction of costimulatory molecules CD28 and CD27 expression levels and the number of population divisions in culture from a limited subset of signaling proteins. The multivariate analysis highlights the information content of both averaged biomarker values and heterogeneity metrics for prediction of cellular age within a T cell population.

Localisation of high acid phosphotyrosine phosphatase activity in afferent arterioles and glomeruli of human kidney

Endothelial cells contain a variety of specific protein tyrosine phosphatases and an acid phosphatase differing from other known phosphatases. The highest activity of this acid phosphatase with artificial or unspecific substrates is present in the afferent arterioles and glomeruli of human kidney, and the activity is inhibited by nephrotoxic fluoride concentrations, suggesting that it plays a role in circulatory regulation. Here the activity was characterised with physiological substrates. An incubation mixture containing phosphotyrosine or phosphoserine was stable at pH 5 when phosphate-precipitating lead was chelated with tartrate. The activities were studied in frozen sections. Only phosphotyrosine was hydrolysed by some cells. High activity of tartrate-resistant phosphotyrosine phosphatase was present in lymphocytes, endothelial cells of afferent arterioles, and glomerular mesangial cells of kidney, decidual cells, and alveolar macrophages. In lymphocytes the activity was fluoride-resistant and vanadate-sensitive, in other cells fluoride- and vanadate-sensitive. In decidual cells and alveolar macrophages, the activity is due to specific osteoclastic/macrophagic tartrate-resistant acid phosphatase, in lymphocytes to specific protein tyrosine phosphatases, and in endothelial and mesangial cells to a protein tyrosine phosphatase-like acid phosphatase. The results suggest that in endothelial cells of the afferent arterioles, mesangial cells, and lymphocytes the cellular activities are regulated by high constitutive phosphotyrosine phosphatase activity and this may be related to the exceptional cyclosporin A sensitivity of these cells.

Inhibition of human renal acid phosphatases by nephrotoxic micromolar concentrations of fluoride

Fluoride is considered to be a nephrotoxic substance, due to the association of 50-180 microM serum concentrations of fluoride with dose-related, subclinical to overt clinical renal impairment. At these concentrations the cellular targets of fluoride in renal tissue remain unknown. Fluoride at micromolar concentrations inhibits some enzymes including phosphatases. Here the effects of fluoride on a recently characterized acid phosphatase complex present only in a few human tissues were studied. This enzyme complex consists of alkaline fixation-resistant beta-glycerophosphatase and tartrate-resistant a-naphthyl phosphatase, and these are different from activities of known types of acid phosphatase and specific phosphatases. In kidney, strong activities for this complex are detected only in the endothelium of the afferent arterioles and in glomeruli. It appeared that alkaline fixation-resistant and lysosomal acid phosphatase activities were significantly inhibited in afferent arterioles and glomeruli by 75 microM fluoride. Tartrate-resistant activity was significantly inhibited by greater concentrations (250 microM). Inhibition of acid phosphatases in the afferent arterioles and glomeruli may be one renal target of fluoride nephrotoxicity. Although the physiological substrates of this acid phosphatase complex are unknown, its specific and restricted location may indicate a role in regulation of renal circulation.