background: there are two subclasses of human iga (iga1 and iga2) that differ in antigenic properties and in chemical composition. the constant domains of α1 and α2 heavy chains have >95% sequence homology though major structural differences exist in the hinge region. quantitation of iga subclass levels depends on the availability of monoclonal antibodies (mabs) specific for conserved conformat...

This paper reports a reconfigurable microfluidic dilution device for high-throughput quantitative assays, which can easily produce discrete logarithmic/binary concentration profiles ranging from 1 to 100-fold dilution in parallel from a fixed sample volume (e.g., 10 μL) without any assistance of continuous fluidic pump or robotic automation. The integrated dilution generation chip consists of s...

To determine whether the sensitivity of the human long-term culture-initiating cell (LTC-IC) assay could be increased, we have evaluated a spectrum of different fibroblast cell lines for their abilities to influence the number of cells detectable as LTC-IC, to influence LTC-IC maintenance, and/or to influence LTC-IC differentiation into colony-forming cells (CFC) in cocultures containing variou...

Induction of neonatal tolerance leads to a profound reduction in cytotoxic T-lymphocyte precursor frequencies against the tolerated alloantigen ("tolerogen") as evaluated by limiting-dilution analysis. The curves obtained were linear within the range tested and, thus, did not yield evidence for any dissociation of cytotoxic precursors from regulatory cell populations. However, it could be shown...

Detailed analyses of simian immunodeficiency virus (SN)-specific cytotoxic T lymphocyte (CTL) responses in vaccinated and infected macaques may help to clarzfi the role of CTL immunity in protection against lentiviruses. Here, the optimal conditions for the measurement of SIV Gag-specific CTL were investigated by bulk and limiting dilution assays of peripheral blood mononuclear cells (PBMC) fro...

There are currently no standardized phenotypic methods for the screening and detection of AmpC enzymes. This study aimed to evaluate different methods to detect AmpC enzymes in Escherichia coli, Klebsiella spp., and Proteus spp., comparing the results from two disk-based methods and an agar dilution method. AmpC activity was determined for 255 clinical isolates by use of a three-dimensional enz...

We have studied the metabolism of benzo(a)pyrene (BP) by intact mouse hepatoma cells, at nM concentrations of the carcinogen, using an assay in which we directly measure the rate of BP fluorescence disappearance. The rate of BP metab olism is half-maximal, at limiting cell dilution, when the concen tration of BP is about 4 nM. This apparent Kmfor BP metabolism is much lower than those reported ...

The accuracy of different methods for the quantitation of hepatitis C virus in plasma was measured with samples from individuals infected with different genotypes and by using RNA transcripts of predetermined concentrations. Highly reproducible results were observed upon repeat testing of samples by both the original version of the Chiron branched-DNA (bDNA) assay (Quantiplex RNA assay; bDNA-1)...

We have studied the metabolism of benzo(a)pyrene (BP) by intact mouse hepatoma cells, at nM concentrations of the carcinogen, using an assay in which we directly measure the rate of BP fluorescence disappearance. The rate of BP metabolism is half-maximal, at limiting cell dilution, when the concentration of BP is about 4 nM. This apparent Km for BP metabolism is much lower than those reported p...