Showing papers by "Lothar Rink published in 1997"

Zinc supplementation reconstitutes the production of interferon-alpha by leukocytes from elderly persons.

Abstract: The elderly are more prone to virus infections and neoplasias than are young adults. During a virus infection, interferon-α (IFN-α), proteins with antiviral, antiproliferative, and immunomodulatory properties, are transiently expressed. We here report that peripheral white blood cells from 16 subjects with a mean age of 72 years yielded less IFN when stimulated with a virus in vitro than those from 16 young adults with a mean age of 28 years. Monocytes are the main source of this IFN. However, yields of another monocyte product, interleukin-6 (IL-6), were greater in cells from the older subjects than from the young adults, so there is no general defect in monocytes from the former. Immunodeficiency in the elderly has been reported to be associated with a deficiency of zinc. When cultures of white blood cells from the elderly were supplemented with 15 μM zinc (the physiologic concentration), they produced IFN in amounts comparable to those from the younger subjects.

Zinc inhibits interleukin-1-dependent t cell stimulation

Abstract: Zinc is a trace element which is essential for immune functions. It directly induces monokine secretion by monocytes; however, effects of zinc on T cells appear contradictory. Apart from enhanced lymphocyte proliferation in peripheral blood mononuclear cells (PBMC), inhibitory properties of high zinc dosages have also been described. In this study, PBMC failed to produce lymphokines like interferon (IFN)-gamma after stimulation with zinc in a serum- and LPS-free cell culture system, whereas monokine secretion [interleukin (IL)-1 beta] occurred. Zinc-uptake studies with the zinc-specific fluorescent probe zinquin revealed that zinc is taken up by PBMC within a few minutes, reaching nearly equal levels in PBMC, isolated monocytes, and T cells. However, if zinc was depleted 1 h after monocyte induction, zinc-free pre-cultured T cells were stimulated to secrete IFN-gamma by zinc-induced monokines. Furthermore, the necessity for a cell-cell interaction between monocytes and T cells for IFN-gamma induction was elucidated. Zinc ions inhibited the proliferation of the IL-1-dependent T cell line D 10N in a dose-dependent manner, suggesting a direct inhibitory effect of zinc. By immunoprecipitation we revealed a specific inhibition of IL-1 receptor-associated protein kinase (IRAK) by zinc ions. Therefore, in contrast to an indirect stimulation of T cells due to zinc-induced monokines, higher concentrations of zinc directly inhibit T cell functions by means of specific inhibition of IRAK and subsequent signaling events such as NF kappa B activation. The divergent effects of zinc on different cell populations, depending on the zinc concentration, could explain contradictory results of zinc stimulation. Furthermore, our data suggest new strategies of specific zinc-mediated immune modulation.

Functional Analysis of Mycoplasma arthritidis-Derived Mitogen Interactions with Class II Molecules

Abstract: The ability of superantigens (SAGs) to trigger various cellular events via major histocompatibility complex (MHC) class II molecules is largely mediated by their mode of interaction. Having two MHC class II binding sites, staphylococcal enterotoxin A (SEA) is able to dimerize MHC class II molecules on the cell surface and consequently induces cytokine gene expression in human monocytes. In contrast, cross-linking with specific monoclonal antibodies or T-cell receptor is required for staphylococcal enterotoxin B (SEB) and toxic shock syndrome toxin 1 (TSST-1) to induce similar responses. In the present study, we report how Mycoplasma arthritidis-derived mitogen (MAM) may interact with MHC class II molecules to induce cytokine gene expression in human monocytes. The data presented indicate that MAM-induced cytokine gene expression in human monocytes is Zn2+ dependent. The MAM-induced response is completely abolished by pretreatment with SEA mutants that have lost their capacity to bind either the MHC class II alpha or beta chain, with wild-type SEB, or with wild-type TSST-1, suggesting that MAM induces cytokine gene expression most probably by inducing dimerization of class II molecules. In addition, it seems that SEA and MAM interact with the same or overlapping binding sites on the MHC class II beta chain and, on the other hand, that they bind to the alpha chain most probably through the regions that are involved in SEB and TSST-1 binding.

One-way synergistic effect of low superantigen concentrations on lipopolysaccharide-induced cytokine production.

Abstract: Lipopolysaccharides (LPS) of gram-negative bacteria and superantigens of gram-positive bacteria are among the main causes of sepsis and septic shock. Symptoms are initiated primarily by the release of endogenous mediators, especially cytokines. In the last few years, increasing evidence for the clinical relevance of mixed sepsis caused by coinfections with both types of bacteria has been found. Therefore, we developed an in vitro mixed sepsis model investigating the effect of different superantigen doses, in combination with different LPS concentrations, on cytokine production in human PBMCs using ELISA and RT-PCR. Low, in vivo relevant concentrations of the superantigen toxic shock syndrome toxin-1 (TSST-1) synergistically enhance LPS-induced production of interferon-gamma (IFN-gamma) interleukin-1 beta (IL-1 beta), IL-6, and IL-10, but low LPS has no comparable effect. Signal transduction studies with different inhibitors suggest that this one-way synergism is caused by an interaction between the cAMP and the PIP2 signaling pathway. Furthermore, our findings support the idea that this interaction is one important crossover point of signal transduction pathways by LPS and superantigens, which seems to be predominantly regulated by IFN-gamma and PGE-2. The identification of additional crossover points in the genesis of a mixed sepsis and their selective influence could lead to identical treatment of both gram-negative and gram-positive sepsis.

Exclusion of bioactive contaminations in Streptococcus pyogenes erythrogenic toxin A preparations by recombinant expression in Escherichia coli.

Abstract: The streptococcal erythrogenic exotoxin A (SPEA) belongs to the family of bacterial superantigens and has been implicated in the pathogenesis of a toxic shock-like syndrome and scarlet fever. Concerning its biological activity, mainly T-cell-stimulatory properties, conflicting data exist. In this study, we show that most of the SPEA preparations used so far contain biologically active contaminations. Natural SPEA from the culture supernatant of Streptococcus pyogenes NY-5 and recombinant SPEA purified from the culture filtrate of S. sanguis are strongly contaminated with DNases. We show that natural SPEA induces more tumor necrosis factor alpha (TNF-alpha) than recombinant SPEA, but we also show that DNases are able to induce TNF-alpha. In commercial SPEA preparations, we identified a highly active protease, which was shown not to be SPEB. To exclude these contaminations, we overexpressed SPEA cloned in the effective high-level expression vector pIN-III-ompA2 in Escherichia coli. The expressed SPEA shows the same amino acid composition as natural SPEA, whereas functional studies reported so far were carried out with toxins containing an incorrect amino terminus. We describe the rapid purification of lipopolysaccharide-, DNase-, and protease-free SPEA in two steps from the host's periplasm and its structural characterization by circular dichroism. Our results represent for the first time the production in E. coli of recombinant SPEA with the authentic N-terminal sequence and a proven superantigenic activity. Collectively, our results indicate that immunological studies of superantigens require highly purified substances free of biologically active contaminations.

Microbial superantigens stimulate T cells by the superantigen bridge and independently by a cytokine pathway.

Abstract: Superantigens cross-link the MHC II molecule on accessory cells with the Vβ region of the T cell receptor (TCR). In this study, we compared the capacity of established superantigens for inducing cy...

HLA-dependent heterogeneous T cell response to Mycoplasma arthritidis-derived superantigen (MAS).

Abstract: Mycoplasma arthritidis induces a chronic arthritis in rodents The role of M arthritidis-derived superantigen (MAS) in the arthritis is still a subject of controversy MAS stimulates mouse and human T cells in a V beta-restricted manner with the subsequent liberation of cytokines The presence of the major histocompatibility complex class II molecule is required for such a stimulation In this study we assessed MAS-induced cytokine production in peripheral blood from patients with different rheumatic diseases and controls using an enzyme-linked immunosorbent assay Statistically significant differences in cytokine production in response to MAS stimulation allowed the distinction of high responders and low responders within groups of patients and controls Higher cytokine induction was statistically correlated with the HLA-DR specificities DR4, DR7 and DR12 To confirm these results, murine V beta 81 cytotoxic T lymphocytes (CTL) were stimulated with MAS in the presence of different HLA-DR lymphoblastoid B cells CTL proliferation was only observed in presence of DR4 and DR7 In conclusion, MAS T cell stimulation and its subsequently cytokine production depends on the presence of certain HLA-DR specificities