Human monocyte function in vitro: influence of conditions during transport of blood from patient to laboratory

Quantitative assessment of cell viability based on flow cytometry and microscopy

We compare flow cytometric and microscopic determination of cell viability by fluorescence labeling using calcein acetoxy-methyl-ester and ethidium homodimer-1 as live and dead stain, respectively. Peripheral blood monocytes served as model system and were accumulated applying density gradients. Subsequently, monocytes were further enriched by magnetic-activated or fluorescence-activated cell sorting (MACS, FACS) targeting the antigen CD14. Identical samples were used for flow cytometric and microscopic analysis to allow direct comparison of both analysis methods. More than 1,000 cells were measured for each sample to minimize the measurement uncertainty caused by counting statistics. We observed good agreement of flow cytometric and microscopic viability measurements. On average, the difference in viability measured by flow cytometry and microscopy amounted to (2.7 ± 1.4)% for live staining and (1.7 ± 1.2)% for dead staining. These deviations were similar to the uncertainty of measurement for cell viability, thus demonstrating that both methods delivered equal results. Besides monocytes, comparison of flow cytometric and microscopy viability for MACS enriched CD34-positive cells also showed consistent results.

Monocyte chemotactic properties in hereditary hemochromatosis

Several observations indicate that the innate metabolic defect in hereditary hemochromatosis (HH) leads to a defective function of the monocyte-macrophage system. The present study was performed to investigate the possibility that a defect in migration of cells of the monocyte-macrophage system can explain the abnormal location of the submucosal macrophages in HH. Monocytes isolated from 14 patients with HH were investigated with regard to chemotactic responsiveness (MCR). Two different methods were used at two different laboratories. Casein and zymosan-activated serum were used as attractants. No difference in MCR was found between the control group and the group of HH patients. The conclusion can therefore be drawn that the abnormal location of the macrophages of the gut wall in HH cannot be explained by an inborn abnormality of the function of receptors responsible for the chemotactic activity of the monocyte-macrophage system. It is, however, still possible that local factors responsible for the macrophage migration (gut hormones?) may have defective activity in HH patients.

The gamma-interferon assay for diagnosis of bovine tuberculosis in cattle: conditions affecting the production of gamma-interferon in whole blood culture

The recently developed gamma-interferon (IFN-gamma) assay system for the diagnosis of bovine tuberculosis in cattle has been accredited by the Standing Committee on Agriculture for use in Australia. In this test system, whole blood is incubated with tuberculin purified protein derivative (PPD) antigens for 16 to 24 h. The plasma is then collected and assayed for IFN-gamma production using an enzyme immunoassay (EIA). The assay system has proven to be a rapid, sensitive and inexpensive method for measuring antigen specific cell-mediated reactivity when compared with the more traditional lymphocyte proliferation assay. The IFN-gamma assay is the first in-vitro cellular assay to be used as a routine diagnostic test in veterinary medicine. While the IFN-gamma EIA has been optimised, several conditions affecting the production of IFN-gamma in whole blood culture needed investigation. We determined that optimal IFN-gamma production required the use of heparinised blood, cultured with 20 micrograms/ml of PPD within 8 h of collection. The use of blood collected post mortem resulted in reduced sensitivity for the assay. The kinetics of IFN-gamma release were established as were the effects of intradermal tuberculin testing on the IFN-gamma assay.