Low ferritin levels indicate the need for iron supplementation: strategy to minimize iron-depletion in regular blood donors.

Iron deficiency is a common problem in regular blood donors which can be prevented by timely iron supplementation. Consequently, these donors should be supplied with oral iron in good time. We evaluated the need to use ferritin rather than or in addition to haemoglobin to screen iron deficiency in blood donors. To this end, serum ferritin was measured routinely every 10th donation in 632 long-term and 171 first-time donors. Furthermore, donors with ferritin < 15 microg L-1 were supplemented with iron. The supplementation efficiency was assessed by follow-up haemoglobin levels over the course of five donations in blood donors with high donation frequency. Our results showed that ferritin decreases after 10 donations and with the increase of donation frequency. In 26% of regular donors, ferritin levels were < 15 microg L-1 and 12% of them were anaemic due to low haemoglobin. After iron supplementation, haemoglobin was raised rapidly in donors with initially low haemoglobin, and thus donor deferment was never indicated. In conclusion, regular ferritin measurement is a useful indicator for iron depletion in blood donors. Our data suggested the usefulness of ferritin screening in first-time donors and regular donors with low haemoglobin levels within the normal range.

Cytokine induction by Mycoplasma arthritidis-derived superantigen (MAS), but not by TSST-1 or SEC-3, is correlated to certain HLA-DR types.

Superantigens bind to major histocompatibility complex (MHC) class II molecules on antigen presenting cells and T cells in a V beta-restricted manner. Both cell types are activated resulting in cytokine production. Although the MHC-II binding site for superantigens has been well described, little is known as to whether this binding complex has an influence on cytokine induction. In order to assess superantigen induced cytokine production and its correlation to HLA-DR types, the authors stimulated peripheral blood from 40 subjects with superantigens toxic shock syndrome toxin-1 (TSST-1), staphylococcal enterotoxin C-3 (SEC-3) and Mycoplasma arthritidis-derived superantigen (MAS), and measured cytokine levels thereafter. The HLA-DR type was determined in each subject. A statistical evaluation was carried out between the highest superantigen cytokine induction and the presence of certain HLA-DR types. Whereas MAS presented a statistical association between the highest cytokine production with HLA-DR4, DR7 and DR12, no such associations were observed for TSST-1 and SEC-3. These results demonstrate that T cell stimulation, and consequently its cytokine production by MAS but not by TSST-1 and SEC-3, depends on the presenting HLA-DR type. Because the diverse HLA-DR specificities are given according to the variability of the beta chain of the HLA-DR molecule, the data suggest the participation of the human MHC-II beta chain in the MAS/MHC-II binding.

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

Superantigens cross-link the MHC II molecule on accessory cells with the Vbeta region of the T cell receptor (TCR). In this study, we compared the capacity of established superantigens for inducing cytokine release. The experimental protocol was generated to answer the question whether all superantigen effects are transmitted by the MHC/TCR cross-linkage and induce mainly a T cell response. We found that TSST-1, ExFTA, and SEC3 differed from all other superantigens tested because they stimulated a stronger monokine release. T cell proliferation after challenge with these superantigens was mainly mediated by a cytokine pathway and not by the cross-linkage of MHC and TCR. For the other superantigens, we were able to demonstrate that major immunomodulatory effect is mediated by the superantigen bridge. With the exception of these three superantigens, the proliferative response of superantigens correlated with their Vbeta specificity. Interleukin-1 (IL-1) and IL-6 were induced in monocytes by all superantigens, whereas tumor necrosis factor-alpha (TNF-alpha) was induced in T cells and by some superantigens, also in monocytes. IL-2 was always induced by the superantigen bridge, whereas interferon-gamma (IFN-gamma) was also induced indirectly by monokines. Collectively, our results indicate that not all superantigens are suitable for investigating superantigen-specific effects, as they show indirect (mitogenic) side effects. Observations for an individual superantigen are, therefore, not transferable to all other superantigens.

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

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 8.1 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.

Stimulation of whole blood cultures in patients with ankylosing spondylitis by a mitogen derived from Mycoplasma arthritidis (MAS) and other mitogens.

In this study we compared cytokine production and cell proliferation of immunocompetent cells derived from patients with ankylosing spondylitis (AS) to those from healthy blood donors using a whole blood assay. To this end, blood cell cultures were stimulated with the superantigens MAS (Mycoplasma arthritidis supernatant) and staphylococcal enterotoxin B (SEB) and the plant lectins phytohaemagglutinin (PHA) and concanavalin A (Con A). The number of white blood cells (WBC) and lymphocyte subsets were also determined. Cell proliferation and levels of interferon-gamma (IFN-gamma), interleukin-1 beta (IL-1 beta) and interleukin-6 (IL-6) were measured after stimulation with the different mitogens. An ELISA test was used to analyse supernatant cytokine levels. Individuals with AS showed significantly lower IFN-gamma concentrations and markedly lower cell proliferation rates with all tested mitogens than healthy controls, while there was no significant difference in IL-6 synthesis. IL-1 beta levels were slightly impaired in the patient group, but only blood cell cultures stimulates with MAS showed a statistical significance. Furthermore, there was a significant elevation of leucocytes and lymphocytes in patients with AS resulting in higher numbers of CD4-positive cells, which implies a higher CD4:CD8 cell ratio. CD19- and CD8-positive cells were not significantly distinct compared to healthy controls. This deviation in cytokine levels and cell proliferation points to a suppression of T lymphocytes. A disturbed T-lymphocyte function may play a part in the pathogenesis of AS.

Differential induction of tumor necrosis factor alpha in murine and human leukocytes by Mycoplasma arthritidis-derived superantigen.

Mycoplasma arthritidis-derived superantigen (MAS) is exclusively produced by M. arthritidis, which is the only known mycoplasma to produce a superantigen. As a superantigen, MAS shows properties similar to those of the staphylococcal enterotoxins and related substances, such as binding to major histocompatibility complex (MHC) class II and V beta-specific stimulation of T cells. In this series of experiments, we demonstrate some differences between MAS and other superantigens. MAS induced the production of tumor necrosis factor alpha (TNF-alpha) mRNA in human as well as in murine leukocytes. However, only in murine leukocytes was the mRNA adequately translated into the protein. In human peripheral blood mononuclear cells, we found only small amounts of TNF, whereas in murine spleen cells we detected levels more than three times higher. The proliferative response to MAS has been shown to be restricted to I-E alpha in the murine MHC. Furthermore, TNF was induced in I-E alpha+ bone marrow-derived macrophages by MAS. In these cells, MAS rapidly induced very high levels of TNF and the amounts of mRNA detected correlated to the amount of protein produced. In comparison with other superantigens, including the staphylococcal enterotoxins, toxic shock syndrome toxin 1, and exfoliative toxin A, the failure of MAS to induce TNF-alpha in human peripheral blood mononuclear cells is specific for MAS and not common to all superantigens. The direct activation of bone marrow-derived macrophages also seems to be specific for MAS. These data suggest that the induction of TNF-alpha by MAS is dependent on the strength of binding to the MHC class II molecule.