Comparative analysis between CFSE flow cytometric and tritiated thymidine incorporation tests for beryllium sensitivity

Comparing [3H] thymidine LPT and CFSE assay to assess lymphocyte proliferation in beryllium-exposed sarcoidosis patients

The detection of antigen specific lymphocyte responses plays a vital role in the diagnosis of various diseases. Beryllium-specific [3H] thymidine lymphocyte proliferation test (LPT) is regarded as a gold standard in identifying chronic beryllium disease (CBD) cases. Alternatively, flow cytometric based carboxyfluorescein succinimidyl ester (CFSE) assay, has several benefits as opposed to LPT, since it further permits both phenotypical characterization and functional analysis of proliferating lymphocyte subsets. The suitability of both LPT and CFSE assay to therefore detect beryllium sensitivity in a group of Be-exposed sarcoidosis patients with suspected beryllium exposure, was evaluated in this study. The clinical relevance of the test responses, expressed as stimulation indices (SI), were additionally compared on a group and individual level. Agreement in clinical interpretation of the test responses between both methods was observed in 4 out of 5 recruited patients, when considering total lymphocyte population i.e., CD3+ and CD19+-cells combined, on day 7 and with CFSE-SI >1.5, when compared with LPT-SI >2.5. Variability in responses to beryllium was additionally evaluated in Be-exposed sarcoidosis patients and compared with healthy controls. To conclude, both LPT and CFSE assay are suitable assays to detect Be sensitivity in Be-exposed sarcoidosis patients. At the same time, flow cytometric based CFSE assay has the edge over LPT in identifying the relevant proliferating lymphocyte populations. As such, when comparing two or more methods, factors that contribute to assay variability such as timepoints, lymphocyte subsets and number of replicates should always be accounted for.

Methods to Assess Proliferation of Stimulated Human Lymphocytes In Vitro: A Narrative Review

The ability to monitor lymphocyte responses is critical for developing our understanding of the immune response in humans. In the current clinical setting, relying on the metabolic incorporation of [³H] thymidine into cellular DNA via a lymphocyte proliferation test (LPT) is the only method that is routinely performed to determine cell proliferation. However, techniques that measure DNA synthesis with a radioactive material such as [³H] thymidine are intrinsically more sensitive to the different stages of the cell cycle, which could lead to over-analyses and the subsequent inaccurate interpretation of the information provided. With cell proliferation assays, the output should preferably provide a direct and accurate measurement of the number of actively dividing cells, regardless of the stimuli properties or length of exposure. In fact, an ideal technique should have the capacity to measure lymphocyte responses on both a quantitative level, i.e., cumulative magnitude of lymphoproliferative response, and a qualitative level, i.e., phenotypical and functional characterization of stimulated immune cells. There are many LPT alternatives currently available to measure various aspects of cell proliferation. Of the nine techniques discussed, we noted that the majority of these LPT alternatives measure lymphocyte proliferation using flow cytometry. Across some of these alternatives, the covalent labelling of cells with a high fluorescence intensity and low variance with minimal cell toxicity while maximizing the number of detectable cell divisions or magnitude of proliferation was achieved. Herein, we review the performance of these different LPT alternatives and address their compatibility with the [³H] thymidine LPT so as to identify the "best" alternative to the [³H] thymidine LPT.

Novel Nanoparticulate and Ionic Titanium Antigens for Hypersensitivity Testing

Titanium is used in a wide variety of materials ranging from medical devices to materials used in everyday life. Adverse biological reactions that could occur in patients, consumers, and workers should be monitored and prevented. There is a lack of available agents to test and predict titanium-related hypersensitivity. The aim of this study was to develop two bioavailable titanium substances in ionic and nanoparticulate form to serve as antigens for hypersensitivity testing in vitro. Peripheral blood mononuclear cells from 20 test subjects were stimulated with the antigens and secretion of monocytic and lymphatic cytokines and chemokines were measured by a multiplex bead assay. Lymphocyte stimulation indices were also determined in a subset of test subjects by measuring CD69 and HLA-DR expression by flow cytometry. Cytokine profiling revealed that both antigens increased production of typical monocyte and macrophage secreted cytokines after 24 h, with significant increases in IL-1β, IL-7, IL-10, IL-12, IL-2R, IL-6, GM-CSF, TNF-α, IL-1RA, MIP-1α, MIP-1β, IFN-α, and IL-15. Lymphatic cytokines and chemokines were not significantly induced by activation. After seven days of stimulation, ionic-Ti (2.5 μg/mL) caused proliferation (stimulation index > 2) of CD4+ cells and CD8+ cells in all persons tested (N = 6), while titanium dioxide nanoparticles (50 μg/mL) only caused significant proliferation of CD4+ cells. Our preliminary results show that the experimental titanium antigens, especially the ionic form, induce a general inflammatory response in vitro. A relevant cohort of test subjects is required to further elucidate their potential for predictive hypersensitivity testing.

Detection of nickel and palladium contact hypersensitivity by a flow cytometric lymphocyte proliferation test

We established a flow cytometric lymphocyte proliferation test (LPT) for the detection of nickel (Ni) and palladium (Pd) sensitization. Eighty-one consecutive patients with an indication for patch test (PT) were tested by LPT with Ni (NiSO4 ) and Pd (Na2 PdCl4 and PdCl2 ) salts. The imprecision of the LPT was low (coefficient of variation 7.2%). Using PT as a diagnostic reference, the sensitivity and specificity of LPT were 74.4% and 80% for NiSO4 , 74.4% and 78.3% for Na2 PdCl4 , and 57.2% and 85.4% for PdCl2 , respectively. For both Ni and Pd, the likelihood ratio for a positive PT markedly increased with increasing LPT value. With medical history as a reference, the sensitivity and specificity were 40.6% and 82.1% for LPT and 59.4% and 89.7% for PT, respectively. Combination of LPT and PT resulted in a higher specificity of 95%, albeit lower sensitivity of 34.4%. In conclusion, flow cytometric LPT represents a reliable and useful method for the detection of Ni and Pd sensitization. LPT values correlate with PT results and, when used in combination with PT, increase test specificity.

Functional consequences of platelet binding to T lymphocytes in inflammation

Expression of the scavenger receptor CD36 on lymphocytes is intriguing. We observed that a minor subpopulation of lymphocytes expressed CD36 on the cell surface. We investigated the source of CD36 and also the proliferation and cytokine production of these CD36(+) CD4(+) lymphocytes. Flow cytometry analysis and immunofluorescence microscopy showed that CD36(+) platelets were responsible for CD36 detection on lymphocytes. CD36 was then used as a tool to characterize lymphocytes with bound platelets. Activation-induced proliferation was lower in CD4(+) lymphocytes with bound platelets than lymphocytes without bound platelets. IL-17 and IFN-γ production was also reduced in lymphocytes with bound platelets. We then studied the presence of CD36(+) CD4(+) lymphocytes in RA patients. We observed that the percentage of CD4(+) lymphocytes with bound platelets was higher on RA patients than in healthy donors. RA patients with higher titers of anti-CCP, RF levels, and cardiovascular risk index presented a lower percentage of CD4(+) lymphocytes with bound platelets. These patients also had higher IL-17 and IFN-γ production. These results suggest that platelet-binding modifies lymphocyte function. This binding could be a regulatory mechanism in RA that confers a less severe phenotype.

Mucosal tolerance to a combination of ApoB and HSP60 peptides controls plaque progression and stabilizes vulnerable plaque in Apob(tm2Sgy)Ldlr(tm1Her)/J mice

Oral tolerance to auto antigens reduces the development of atherosclerosis in mouse models. However, the effect of immune tolerance to multiple self antigenic peptides in plaque progression and stabilization is not known. We studied the protective effect of mucosal tolerance to peptides from apolipoprotein B (ApoB; 661–680) and heat shock protein 60 (HSP60; 153–163), in combination with diet, in the prevention of atherosclerotic lesion progression and plaque stabilization in ApoB^tm25gyLDLr^tm1Her mice. We found that oral administration of five doses of a combination of ApoB and HSP60 peptides (20 µg/mice/dose) induced tolerance to both the peptides and reduced early plaque development by 39.9% better than the individual peptides (ApoB = 28.7%;HSP60 = 26.8%)(P<0.001). Oral tolerance to combination of peptides along with diet modification arrested plaque progression by 37.6% which was associated with increases in T-regulatory cell and transforming growth factor-β expression in the plaque and peripheral circulation. Reduced macrophage infiltration and tumor necrosis factor-α expression in the plaque was also observed. Tolerance with continued hypercholesterolemia resulted in 60.8% reduction in necrotic core area suggesting plaque stabilization, which was supported by reduction in apoptosis and increased efferocytosis demonstrated by greater expression of receptor tyrosine kinase Mer (MerTK) in the plaque. Tolerance to the two peptides also reduced the expression of matrix metalloproteinase 9, tissue factor, calprotectin, and increased its collagen content. Our study suggests that oral tolerance to ApoB and HSP60 peptide combination induces CD4⁺ CTLA4⁺ Tregs and CD4⁺CD25⁺Foxp3⁺ Tregs secreting TGF-β, which inhibit pathogenic T cell response to both peptides thus reducing the development and progression of atherosclerosis and provides evidence for plaque stabilization in ApoB^tm25gyLDLr^tm1Her mice.

Activation of inflammatory cells and cytokines by peptide epitopes in vitro: a simple in-vitro screening assay for prioritizing them for in-vivo studies

OBJECTIVE

Antigen-specific immune modulation is an attractive approach to atherosclerosis treatment. The aim of this study was to develop an in-vitro assay to screen peptide molecules for their inflammatory propensity.

MATERIALS

Human dendritic cells derived from CD14(+) monocytes were activated using peptides derived from apolipoprotein B100 (ApoB), heat shock protein 60 (HSP60) and complement cascade (peptide A) in vitro, and used for priming autologous T cells. Proliferation of T cells, their differentiation to regulatory cells (Treg) and their cytokine profile were studied. The efficacy of the peptides in preventing atherosclerosis was studied in ApoB(tm2Sgy)/Ldlr(tm1Her/J) knockout mice.

RESULTS AND CONCLUSION

ApoB and HSP60 peptides induced T-cell proliferation and expansion of regulatory T cells with interleukin-10 and transforming growth factor-β secretion. In comparison, peptide A was a poor stimulator of T cells and was found to induce tumor necrosis factor-α secretion by activated T cells. ApoB and HSP60 peptides were found to reduce early atherosclerotic lesion formation in mice by 32.1 and 33.5 %, respectively, while the reduction with peptide A was 5.7 %. Thus the in-vitro assay shows an apparent correlation with in-vivo activity and can be developed as a screening assay to prioritize the candidate molecules for animal efficacy testing.

Flow cytometry applications for exotic animals

This article describes applications of flow cytometry in hematology. It includes a basic description of how flow cytometers work and their use in enumerating cell populations based on phenotypic markers and measurement of cell functions. Challenges presented by limitations of reagents for exotic animals are described in addition to sources of cross-reactive antibodies.