DNA analysis of stimulated lymphocytes by automatic sampling for flow cytometry

Gingipains in the culture supernatant of Porphyromonas gingivalis cleave CD4 and CD8 on human T cells

Porphyromonas gingivalis has been shown to attack host defense systems through proteolytic cleavage of a wide variety of members of the systems. In this study, we examined the ability of P. gingivalis culture supernatant to alter the expression of human T cell surface proteins. As judged by flow cytometric analysis, detection of CD4 expression was completely eliminated by the supernatant, but CD8 was less sensitive. When the culture supernatant was added with reducing agents, proteolytic activity was enhanced, resulting in the cleavage of CD8. Mitogenic response of T cells to phytohemagglutinin or concanavalin A was decreased by the treatment of the cells with the culture supernatant of P. gingivalis. The three forms of gingipains (high molecular mass arginine-specific gingipain, arginine-specific gingipain 2 and lysine-specific gingipain) purified from the culture supernatant of P. gingivalis actively cleaved CD4 and CD8 on human T cells, indicating that proteolytic activity of the culture supernatant was due to gingipains. These results suggest that cysteine proteinases like gingipains released from P. gingivalis cleave T cell surface proteins and impede T cell function.

Nonradioactive alternative to clinical mixed lymphocyte reaction

The MLR is used clinically as a functional assay for genetic HLA disparity. Traditionally this test relies on [3H]thymidine incorporation to detect T-cell proliferation as an indicator of alloantigenicity. Environmental and administrative concerns regarding radioisotope use and disposal have encouraged the development of sensitive, nonradioactive assay for T-cell alloactivation. We describe a nonradioactive alternative to the clinical MLR which uses an IL-2-dependent cell line, CTLL20.3, and MTT reduction to detect IL-2 accumulation in MLC SNs as an index of T-cell alloactivation. We first determined (a) the optimal number of CTLL20.3 cells for the assay, (b) the optimal time of SN analysis for IL-2, and (c) additional manipulations that significantly increase the assay sensitivity for IL-2. Using this assay system with patient lymphocyte combinations, we demonstrated that the CTLL20.3-MTT assays correlate well with the [3H]thymidine assays of T-cell proliferation for the detection of MHC incompatibility. Indeed, the CTLL20.3-MTT assay may be slightly more sensitive than the traditional clinical MLR.

Methodological Analysis of Flowcytometric Measurements of Nuclear Dna in Oncology

The application of specific and proven guidelines is required for flow cytometric nuclear DNA analysis, which can provide precise information on genomic quantitative modifications and the proliferative activity of tumour tissues, clinically useful for prognosis and monitoring of therapy and recurrencies. The authors review the various protocol phases to be followed for a correct analysis and discuss the main problems that can be encountered in the procedural steps and in interpreting the histograms.

A novel B cell stimulation/proliferation assay using simultaneous flow cytometric detection of cell surface markers and DNA content

Assessment of the specific B cell proliferative response by thymidine incorporation following polyclonal stimulation (e.g. with pokeweed mitogen or B cell growth factor) is problematic whenever the proportion of B cells in a particular sample is low as in blood samples. Here we describe a simple assay consisting of identifying the cultured B cells with anti-CD19/CD20 fluorescein-conjugated antibody and simultaneously using propidium iodide DNA staining to determine the percent of S/G2/M phase cells among the gated B cells. This assay can be used to determine B cell responsiveness even in individuals with very low blood B cell counts (e.g., in recipients of bone marrow transplant), does not require laborious B cell purifications and does not involve radiation hazard.

Phenotypic analysis of human peripheral blood lymphocytes by automatic sampling flow cytometry after stimulation with mitogens or allogeneic cells

Human peripheral blood lymphocyte (PBL) phenotypes have been analyzed before and after stimulation with phytohemagglutinin (PHA), concanavalin A (ConA) and pokeweed mitogen (PWM) for 3 days and in mixed lymphocyte culture (MLC) for 7 days. PBL labeled with each of 10 fluorescent monoclonal antibodies were automatically sampled for flow cytometry from 96-well microtiter plates using a microsample delivery system. The reference phenotypic ranges were determined in fresh cells and control cultures. PHA was mostly mitogenic for T PBL bearing the CD3, CD5, CD7, CD8 and CD25 differentiation clusters, and a low density of CD1 and CD4 had a small effect on human natural killer cells (HNK) and also did not stimulate B (CD19) and HLA-DR+ PBL. There was an incomplete phenotypic overlapping between PHA- and ConA-stimulated cultures, ConA being more mitogenic for CD4 and less mitogenic for CD8 PBL. The mitogenic effect of PWM was evident on CD3, CD5, CD7, CD4, CD25 and CD8, but not on HNK, HLA-DR and CD19 B PBL, which presumably had already differentiated into antibody-secreting cells. After MLC stimulation all T, B and HNK PBL subsets tested were increased, but the cells bearing CD1, CD4, CD5, CD7, CD25, HNK, CD19 and HLA-DR had the greatest proliferation with respect to the unmixed control PBL. The present approach to the phenotyping of PBL subsets could offer more complete and accurate data for monitoring and follow-up of patients in transplantation and immunopathology hospital wards.