Comparison of Serum and Cell-Specific Cytokines in Humans

Abstract

Cytokines function at the cellular, microenvironmental level, but human cytokine assessment is most commonly done at the macro level, by measuring serum cytokines. The relationships between serum and cellular cytokines, if there are any, are undefined. In a study of hospitalized patients in Malawi, we compared cytometrically assessed, cell-specific cytokine data to serum interleukin 2 (IL- ؊ T cells producing induced IL-8 (r s ‫؍‬ ؉0.40 and r s ‫؍‬ ؉0.56, respectively). Thus, the strength of associations between serum and cellular cytokines varied with the presence or absence of bloodstream infection, HIV status, and perhaps other factors we did not assess. These results strongly suggest that serum cytokines at best only weakly reflect peripheral blood cell cytokine production and balances.2Cytokines regulate cellular immune interactions and are produced by lymphocytes, monocytes, macrophages, and, for some cytokines, also fibroblasts, neutrophils, endothelial cells, or mast cells (for a review, see reference 8). Although cytokines function on a microenvironmental level, human cytokines are most commonly assessed at the macro level, by measuring serum and plasma levels or levels in the supernatant of in vitrostimulated blood cells. Reasons for this approach are largely practical. Serum and plasma levels can be readily assessed by using commercially available enzyme immunoassays, while cell-specific cytokine assessment is laborious, involving in situ hybridization, cell separation followed by PCR measurement of mRNA, limiting dilution assays, plaque and enzyme-linked immunospot (ELISPOT) assays, or T-cell cloning. In recent years, improved reagents have permitted flow cytometric cellspecific cytokine assessments in which ex vivo peripheral blood cell stimulation or nonstimulation is followed by cell permeabilization, fixation, fluorescent staining, and cytokine detection (12, 15). With multiparameter flow cytometry, very specific cell populations can be identified by surface antigen staining, without cell separation or cloning, and the production of multiple cytokines by individual cells can be assessed.Given the variety of techniques now used for cytokine assessments, an obvious and pressing question is how the results of these techniques compare to one another. Yet, comparisons of various cytokine assessment techniques have involved only a few cytokines and tend to be qualitative rather than quantitative. In several studies, indirect comparisons were made, or could be made by the reader, between serum or plasma cytokine levels and cytokine mRNA or protein levels in the supernatant of stimulated whole blood cell cultures (2,10,19,27), between serum or plasma and monocytic intracellular interleukin 6 (IL-6) production (24), among all three measures (serum or plasma, supernatant, and intracellular) of gamma interferon (IFN-␥) production (5), and between ELISPOT cytokine results and supernatant levels or intracellular IFN-␥ production (16).In the early publications on intracellular cytokine staining, supernatant an...

Spontaneous Cytokine Production and Its Effect on Induced Production

“…This is somewhat of an assumption in regard to both measures. We have previously shown that, in general, serum and cell-specific cytokines are at best only weakly associated with one another (13). Correlations between cell and serum cytokine parameters were not infrequently even negative, consistent with the hypothesis that serum and cell-specific cytokines measure different things (13).…”

“…We have previously shown that, in general, serum and cell-specific cytokines are at best only weakly associated with one another (13). Correlations between cell and serum cytokine parameters were not infrequently even negative, consistent with the hypothesis that serum and cell-specific cytokines measure different things (13). Interestingly, for the patients with spontaneous cytokine production discussed here, the correlations between serum and peripheral-blood cell-specific cytokines were all in a positive direction but, as with the more general population, generally with only weak correlation coefficients (this study).…”

Cytokine profile of murine malaria: stage-related production of inflammatory and anti-inflammatory cytokines

“…Despite many research studies involving serum and plasma cytokine assessments, this approach does have a number of limitations. Serum and plasma cytokine levels can be affected by receptor binding, temperature degradation, urinary excretion, and cytokine breakdown within reacting cells (15). To be more precise, the present study demonstrated the role of some inflammatory (i.e., IFNγ, IL-12p40, IL-6 and TNFα) and anti-inflammatory (i.e., IL-4 and IL-10) cytokines mRNA extracted from liver and spleen tissues, as they are considered to be the most affected organs.…”

Plasma Cytokines and Future Risk of Non-Hodgkin Lymphoma (NHL): A Case-Control Study Nested in the Italian European Prospective Investigation into Cancer and Nutrition

“…Blood cytokines are produced not only by those cell types considered to play pivotal roles in the immune system as well as in inflammatory responses, including lymphocytes, monocytes, and mast cells, but also by macrophages and, for some cytokines, also fibroblasts, neutrophils, and endothelial cells (26). So, it should be NOTE: ORs estimated by CLR models for tertiles of plasma cytokine concentrations (tertile cut points based on the distribution of cytokine levels for control subjects).…”