Effective concentration of intravenous immunoglobulin for neutralizing Panton-Valentine leukocidin in human blood.

Community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) infects healthy individuals, although the precise cause remains unclear. CA-MRSA produces Panton-Valentine leukocidin (PVL), which often causes severe invasive infection; however, antitoxin drugs against PVL are limited. Intravenous immunoglobulin (IVIg) possesses antitoxin activity, but unfortunately, the optimal dose is unknown. Here, we measured the PVL neutralizing antibody titer in the plasma of Japanese individuals and sera of American donors. Next, we compared the cytotoxic effects of PVL on neutrophils in phosphate buffered saline (PBS) or whole blood to determine the effect of the neutralizing antibody. Finally, we evaluated the effective concentration of IVIg required to neutralize PVL in PBS and whole blood. We observed that the titer of PVL neutralizing antibody in healthy individuals polarized as high and low/none group. Additionally, the PVL neutralizing antibody titer considerably affected the concentration at which IVIg elicited its effect. This suggests that PVL-producing CA-MRSA might be involved in determining the severity of infection in healthy individuals without neutralizing antibody against PVL. The neutralizing effect of IVIg was observed in both PBS and whole blood. However, the optimal concentration of IVIg required for neutralizing PVL varied between PBS and whole blood. In addition, since the PVL-neutralizing activity of IVIg also largely depends on blood composition, such as neutralizing antibody concentration, the optimal dosage of IVIg as an antitoxin drug should be decided in a timely manner after considering the patient's medical background.

Intravenous Immunoglobulin Suppresses Abortion Relates to an Increase in the CD44bright NK Subset in Recurrent Pregnancy Loss Model Mice.

Recurrent pregnancy loss (RPL), which mostly is of unknown etiology (unexplained RPL, uRPL), is defined as three or more consecutive spontaneous abortions. Some women with uRPL display a higher fraction and cytotoxicity of natural killer (NK) cells in the periphery and endometrium. Therefore, some uRPL cases have been explained by autoimmune abnormalities. The efficacy of intravenous immunoglobulin (IVIg) for uRPL has been confirmed in several clinical trials; however, its mechanism remains unknown, mainly because the abortion mechanism remains to be elucidated. In the present study, we analyzed the mechanisms of both abortion and IVIg action using a uRPL mouse model in which abortion was induced by lipopolysaccharide injection. IVIg attenuated the abortion rate in the uRPL model mice. The suppressive effect of IVIg was maximized by high dose administration early after lipopolysaccharide injection. Specifically, we discovered the presence of two distinct uterine NK (uNK) subsets: CD44(bright) and CD44(mid) In uRPL model mice, we observed an increase in the number of CD44(bright) uNK cells, while the CD44(mid) uNK subset remained unchanged. Furthermore, when abortion was reduced by IVIg administration, the cell number of the CD44(bright) uNK subset did not increase, which might allow differentiating pathological from normal uNK cells based on CD44 expression. Based on these results, we propose not only an effective administration protocol of IVIg to the uRPL model mice, but also a novel mechanism of abortion related to the increase in the CD44(bright) subset and of IVIg, which suppresses the increase of the CD44(bright) subset.

Intravenous immunoglobulin preparation prevents the production of pro-inflammatory cytokines by modulating NFκB and MAPKs pathways in the human monocytic THP-1 cells stimulated with procalcitonin.

OBJECTIVE: In the previous investigations, we showed that intravenous immunoglobulin (IVIG) prevented cytokine release in procalcitonin (PCT)-stimulated monocytic cells. The aim of the present study was to investigate the underlying mechanisms of inhibition of IVIG on cytokine production in PCT-stimulated THP-1 cells. METHODS: THP-1 cells treated with phorbol myristate acetate were stimulated with PCT. The protein levels of pro-inflammatory cytokines [tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and high-mobility group box 1 (HMGB1)] in the culture supernatants were determined using enzyme-linked immunosorbent assay kits. The mRNA level of TNF-α was determined by reverse transcription-polymerase chain reaction. The phosphorylations of nuclear factor kappa B (NFκB) and the mitogen-activated protein kinases (MAPKs) were determined by Western blotting. RESULTS: IVIG reduced mRNA expression and protein production of TNF-α in PCT-stimulated THP-1 cells. Not only IVIG but also both the Fc fragment and the F(ab')2 fragment inhibited PCT-induced TNF-α, IL-6, and HMGB1 production. Furthermore, IVIG and its fragments suppressed PCT-induced phosphorylations of NFκB, p38 MAPK, and c-Jun N-terminal kinase. CONCLUSIONS: Our results indicate that IVIG prevents PCT-induced cytokine production mediated by not only the Fab region but also the Fc region. The activity of IVIG and its fragments might be regulated by inhibiting NFκB and MAPKs pathways in THP-1 cells.

Intravenous immunoglobulin preparation attenuates neurological signs in rat experimental autoimmune neuritis with the suppression of macrophage inflammatory protein -1α expression.

To clarify the mechanism of action of an intravenous immunoglobulin (IVIG) preparation in chronic inflammatory demyelinating polyneuropathy, the effects of IVIG were investigated using an experimental autoimmune neuropathy model in the rat. IVIG significantly suppressed the progression of neurologic signs and sciatic nerve conduction velocity with the inhibition of inflammatory cell infiltration, mainly of macrophages, to the peripheral nerves. A significant suppressive effect on the expression of macrophage inflammatory protein 1-α (MIP-1α) was simultaneously observed in the nerves. These results suggest that IVIG is effective for inflammatory demyelinating polyneuropathy by inhibiting the chemotactic factor of macrophages.

An fc gamma receptor-mediated upregulation of the production of interleukin 10 by intravenous immunoglobulin in bone-marrow-derived mouse dendritic cells stimulated with lipopolysaccharide in vitro.

Intravenous immunoglobulin (IVIG), a highly purified immunoglobulin fraction prepared from pooled plasma of several thousand donors, increased anti-inflammatory cytokine IL-10 production, while decreased proinflammatory cytokine IL-12p70 production in bone-marrow-derived mouse dendritic cells (BMDCs) stimulated with lipopolysaccharide (LPS). The changes of cytokine production were confirmed with the transcription levels of these cytokines. To study the mechanisms of this bidirectional effect, we investigated changes of intracellular molecules in the LPS-induced signaling pathway and observed that IVIG upregulated ERK1/2 phosphorylation while downregulated p38 MAPK phosphorylation. Using chemical inhibitors specific to protein kinases involved in activation of Fc gamma receptors (FcγRs), which mediate IgG signals, we found that hyperphosphorylation of ERK1/2 and Syk phosphorylation occurred after stimulation of BMDC with LPS and IVIG, and the increasing effect on IL-10 production was abolished by these inhibitors. Furthermore, an antibody specific to FcγRI, one of FcγRs involved in immune activation, inhibited IVIG-induced increases in IL-10 production, but not IL-12p70 decreases, whereas the anti-IL-10 antibody restored the decrease in IL-12p70 induced by IVIG. These findings suggest that IVIG induced the upregulation of IL-10 production through FcγRI activation, and IL-10 was indispensable to the suppressing effect of IVIG on the production of IL-12p70 in LPS-stimulated BMDC.

Design, synthesis, and biological evaluation of novel estradiol-bisphosphonate conjugates as bone-specific estrogens.

Bone deficiency causes osteoporosis and often decreases quality of life in patients with rheumatoid arthritis. Estrogens are known to protect elderly women from bone loss. Synthesis of new estradiol-bisphosphonate conjugates (E(2)-BPs) was accomplished and their in vivo activity as bone-specific estrogens were examined. Among them, MCC-565 showed selective estrogenic activity in bones; but it showed little estrogenic activity in the uterus. We also found that the linker moiety in E(2)-BPs was essential for the absorption and specificity of the conjugates.

Isolation of Zn2+ as an endogenous agonist of GPR39 from fetal bovine serum.

We attempted to determine natural agonists of GPR39 in fetal bovine serum (FBS). FBS was conditioned to extract peptides and fractionated by two types of HPLC. The activity of each fraction was monitored by intracellular calcium mobilization. Then the purified active ingredient was analyzed by inductively coupled plasma mass spectrometry. In this fashion, Zn2+ ion was identified as an agonist of GPR39, though no peptidergic molecules were found. The calcium-mobilizing activity of Zn2+ was not abolished by pertussis toxin but was by a phospholipase C (PLC) inhibitor, U73122, indicating that the activity of GPR39 is mediated through the Gqalpha -PLC pathway. In addition, Zn2+ also activated mouse and rat GPR39, showing that the function of GPR39 as a Zn2+ receptor is conserved across species. This study is the first exploration of GPR39 agonists in FBS and indicates that GPR39 functions as a Gq-coupled Zn2+-sensing receptor.