Modulation of dendritic cells and regulatory T cells by naturally occurring antibodies

Is there a Role of Intravenous Immunoglobulin in Immunologic Recurrent Pregnancy Loss?

Recurrent pregnancy loss (RPL) commonly refers to three or more miscarriages that occur before 20 weeks of pregnancy. The immunological cause of RPL could be either an auto- or alloimmune-related event or both. Because of the discovery of immunological abnormalities in RPL patients in clinical practice, several immunomodulatory therapies were introduced to maintain the immune balance at the maternal-fetal interface. Intravenous immunoglobulin (IVIg) is one of the immunomodulators. In recent years, several studies have analyzed the therapeutic effect of IVIg on RPL patients with antiphospholipid syndrome (APS) or unexplained RPL. However, their results are controversial. IVIg can be used in RPL patients with APS who have previously failed in other treatments. It is recommended that IVIg infusion could be considered used before conception in RPL patients who have cellular immune abnormalities such as increased natural killer (NK) cell counts, NK cell cytotoxicity, or increased T helper (Th)1/Th2 ratio, depending on the cut-off values of each hospital. The aim of this review was to summarize the mechanisms, efficacy, pharmacokinetics, and side effects associated with passive immunization using IVIg in immunologic RPL, according to the literature published in recent years. We hope that more obstetricians will be able to understand the timing and indication of IVIg properly in immunologic RPL patients and effectively enhance pregnancy outcomes for mothers and neonates.

Intravenous immunoglobulin therapy enhances suppressive regulatory T cells and decreases innate lymphoid cells in children with immune thrombocytopenia

BACKGROUND

This study aimed to investigate the relationship between CD4⁺ regulatory T cells (Tregs) and innate lymphoid cells (ILCs) in children with primary immune thrombocytopenia (ITP) undergoing high-dose intravenous immunoglobulin (IVIG) therapy.

METHODS

We enrolled a cohort of 30 children with newly diagnosed ITP and 30 healthy controls and collected blood samples for levels of Tregs, ILCs, relevant cytokines, and Treg suppression assay at the diagnosis, two days, four weeks, and one year (only platelet count) after high-dose IVIG treatment. IVIG partial responders was defined by a platelet count less than 100 × 10⁹ /L at 12 months after IVIG treatment.

RESULTS

Children with newly diagnosed ITP exhibited elevated levels of ILC1, ILC2, ILC3, Th17, myeloid dendritic cells (DCs), plasmacytoid DCs, and serum IFN-γ and IL-17A levels, accompanied by a decrease in IL-10-producing Tregs. High-dose IVIG therapy reversed these aberrations. Platelet counts positively correlated with Tregs (rho = 0.72) and negatively correlated with both ILC1 (rho = -0.49) and ILC3 (rho = -0.60) (P < 0.05). Significantly lower Tregs and higher ILC1, ILC3, DCs, and serum IL-17A levels were noted in the partial responders (n = 8) versus responders (n = 22; P < 0.05). We found that Tregs suppressed proliferation of ILCs and CD4⁺ T cells in CD25-depleted peripheral PBMCs and enhanced the apoptosis of CD4⁺ CD45RO⁺ T cells in vitro following IVIG therapy.

CONCLUSIONS

Effective high-dose IVIG therapy for children with newly diagnosed ITP appears to result in the induction of Tregs, which suppresses ILC proliferation in vitro and is associated with platelet response.

Immunoglobulin G Enhances Generation of Inducible T Regulatory Cells and Increases Their Regulatory Function

Intravenous immunoglobulin (IVIg) has been shown to be effective in the treatment of a variety of autoimmune diseases. To clarify the role of T regulatory cells (Tregs) in the immunoregulatory effect of IVIg, we focused on human inducible T regulatory cells (iTregs) and investigated the mechanism of action of IVIg. When immunoglobulin G (IgG) was added to a culture system that differentiates iTregs from anti-CD3 antibody activated CD4+CD25- T cells in the presence of syngeneic immature dendritic cells, interleukin (IL)-2 and transforming growth factor-β (TGF-β), the expression of forkhead box P3 (FoxP3), which is the master transcription factor for Tregs in CD4+CD25+ T cells, increased in an IgG concentration-dependent manner. The expression of FoxP3 in iTregs in the 20 mg/mL IgG group was twice as high as that in the saline group. iTregs that highly expressed FoxP3 not only partially suppressed the polyclonal proliferative response of T cells derived from the same individual but also produced significantly more inhibitory cytokines IL-10 and TGF-β. The ability of IgG to enhance iTregs differentiation was also observed in the Fc fragment, but not in the F(ab')₂ fragment. These results suggest the clinical regulation of immune responses by IVIg administration may contribute at least to enhancing the differentiation of iTregs and partial immunosuppressive functions.

IVIg and LPS Co-stimulation Induces IL-10 Production by Human Monocytes, Which Is Compromised by an FcγRIIA Disease-Associated Gene Variant

Intravenous Immunoglobulin (IVIg) is used to treat autoimmune or inflammatory diseases, but its mechanism of action is not completely understood. We asked whether IVIg can induce interleukin-10 (IL-10) and reduce pro-inflammatory cytokine production in human monocytes, and whether this response is reduced in monocytes from people with an Fcγ receptor IIA (FcγRIIA) gene variant, which is associated with increased risk of inflammatory diseases and poor response to antibody-based biological therapy. IVIg increased IL-10 production and reduced pro-inflammatory cytokine production in response to bacterial lipopolysaccharide (LPS), which required FcγRI and FcγRIIB and activation of MAPKs, extracellular signal-regulated kinase 1/2 (ERK1/2), and p38. IL-10 production was lower and pro-inflammatory cytokine production was higher in monocytes from people with the FcγRIIA risk variant and the risk variant prevented IL-10 production in response to (IVIg+LPS). Finally, we show that IVIg did not induce MAPK activation in monocytes from people with the risk variant. Our results demonstrate that IVIg can skew human monocytes to an anti-inflammatory, IL-10-producing activation state, which is compromised in monocytes from people with the FcγRIIA risk variant. This research has profound implications for the use of IVIg because 25% of the population is homozygous for the FcγRIIA risk variant and its efficacy may be reduced in those individuals. In addition, this research may be useful to develop new therapeutic strategies to replace IVIg by cross-linking FcγRIs and FcγRIIBs to promote anti-inflammatory macrophage activation, independent of the FcγRIIA genotype.

Immune modulation of i.v. immunoglobulin in women with reproductive failure

Background

The mechanism of maternal immune tolerance of the semi‐allogenic fetus has been explored extensively. The immune reaction to defend from invasion by pathogenic microorganisms should be maintained during pregnancy. An imbalance between the immune tolerance to the fetus and immune activation to the pathogenic organisms is associated with poor pregnancy outcomes. This emphasizes that the immune mechanism of successful reproduction is not just immune suppression, but adequate immune modulation.

Methods

In this review, the action of i.v. immunoglobulin G (IVIg) on the immune system and its efficacy in reproductive failure (RF) was summarized. Also suggested is the indication of IVIg therapy for women with RF.

Main findings (Results)

Based on the mechanism of the immune regulation of IVIg and following confirmation of the immune modulation effects of it in various aberrant immune parameters in patients with RF, it is obvious that IVIg is effective in recurrent pregnancy losses and repeated implantation failures with immunologic disturbances.

Conclusion

The authors recommend IVIg therapy in patients with RF with aberrant cellular immunologic parameters, including a high natural killer cell proportion and its cytotoxicity or elevated T helper 1 to T helper 2 ratio, based on each clinic's cut‐off values. Further clinical studies about the safety of IVIg in the fetus and its efficacy in other immunologic abnormalities of RF are needed.

Anti-MAG autoantibodies are increased in Parkinson's disease but not in atypical parkinsonism

There is emerging evidence that glial cells are involved in the neuropathological process in Parkinson's disease (PD) in addition to degeneration of neuronal structures. Recently, we confirmed the presence of an adaptive immune response against different glial-derived antigens in PD, with a possible role of anti-MAG, anti-MBP and anti-PLP antibodies in the disease progression. The aim of the present study was to assess humoral response against myelin-associated glycoprotein (MAG) in patients with parkinsonism (both idiopathic and atypical) to check whether these antibodies could serve as biomarkers of PD, its severity and progression. Anti-MAG autoantibodies were measured by an ELISA system in 99 PD patients, 33 atypical parkinsonism patients, and 36 control subjects. In PD patients, anti-MAG IgM autoantibodies were significantly higher in comparison to healthy control subjects (p = 0.038). IgM anti-MAG autoantibodies titers were also significantly higher in the whole group of patients with parkinsonism (either idiopathic or atypical) in comparison to healthy control subjects (1.88 ± 0.84 vs 1.70 ± 1.19, p = 0.017). This difference was mainly driven by the PD group, as the atypical parkinsonism group did not differ significantly from the control group in anti-MAG antibody levels (p = 0.51). A negative correlation between anti-MAG levels and disease duration was found in PD patients. Our study provides evidence for an increased production of autoantibodies against a protein of glial origin in PD. The negative correlation between anti-MAG antibodies and disease duration may suggest possible involvement of the immune system in disease progression. Increasing evidence that glia are involved in the neurodegenerative process to a greater extent than previously thought may turn out be useful in the search for biomarkers of the neurodegenerative process in PD.

Potentiation of cytokine-induced proliferation of human Natural Killer cells by intravenous immunoglobulin G

Intravenous IgG (IVIG) therapy can be used for immunomodulation. IL-2 is an immunoregulatory cytokine. We evaluated IVIG modulation of human blood lymphocyte response to IL-2 and other cytokines. Neither IVIG nor low concentrations of IL-2 (3-30U/ml) induced lymphocyte proliferation, but in combination they synergistically enhanced proliferation of NK cells. The CD56(bright) cells expanded more than CD56(dim) NK cells, with 90% of NK cells dividing up to 8 generations by day 6, while <8% of T cells divided. IVIG also potentiated NK cell proliferation with IL-12, IL-15 and IL-18. The IVIG+cytokine-expanded NK cells were less cytotoxic for K562 cells, than NK cells with cytokine alone. IVIG also enhanced interferon-γ production with IL-2, IL-12 and IL-18. In conclusion, IVIG selectively potentiates NK cell proliferation and interferon-γ secretion with IL-2, IL-12, IL-15 and IL-18 in vitro. These findings warrant evaluation in vivo in relation to NK cells and the immunoregulatory actions of IVIG.

Intravenous immunoglobulins in liver transplant patients: Perspectives of clinical immune modulation

Shortage of appropriate donor grafts is the foremost current problem in organ transplantation. As a logical consequence, waiting times have extended and pretransplant mortality rates were significantly increasing. The implementation of a priority-based liver allocation system using the model of end-stage liver disease (MELD) score helped to reduce waiting list mortality in liver transplantation (LT). However, due to an escalating organ scarcity, pre-LT MELD scores have significantly increased and liver recipients became more complex in recent years. This has finally led to posttransplant decreasing survival rates, attributed mainly to elevated rates of infectious and immunologic complications. To meet this challenging development, an increasing number of extended criteria donor grafts are currently accepted, which may, however, aggravate the patients’ infectious and immunologic risk profiles. The administration of intravenous immunoglobulins (IVIg) is an established treatment in patients with immune deficiencies and other antibody-mediated diseases. In addition, IVIg was shown to be useful in treatment of several disorders caused by deterioration of the cellular immune system. It proved to be effective in preventing hyperacute rejection in highly sensitized kidney and heart transplants. In the liver transplant setting, the administration of specific Ig against hepatitis B virus is current standard in post-LT antiviral prophylaxis. The mechanisms of action of IVIg are complex and not fully understood. However, there is increasing experimental and clinical evidence that IVIg has an immuno-balancing impact by a combination of immuno-supporting and immuno-suppressive properties. It may be suggested that, especially in the context of a worsening organ shortage with all resulting clinical implications, liver transplant patients should benefit from immuno-regulatory capabilities of IVIg. In this review, perspectives of immune modulation by IVIg and impact on outcome in liver transplant patients are described.

Intravenous IgG (IVIG) and subcutaneous IgG (SCIG) preparations have comparable inhibitory effect on T cell activation, which is not dependent on IgG sialylation, monocytes or B cells

IVIG modulates T cell activation in vitro and inflammatory-autoimmune conditions in vivo. Sialylation of IgG, Fc receptor interactions, modulation of monocyte/macrophage/B cell functions have been implicated in IVIG effects. Subcutaneous IgG (SCIG) therapy is increasingly used for IgG replacement but whether these preparations share the effects of IVIG on T cell modulation is not documented. We compared the potency of SCIG-Hizentra™ (20% IgG preparation) with IVIG-Privigen® (10% IgG) for T cell inhibition, and assessed the involvement of IgG sialylation, monocytes and B cells in this process. Human PBMCs or sorted cells were cultured 3-7 days, and T cells were stimulated with immobilized anti-CD3 mAb or Candida antigen. Thymidine incorporation into DNA was quantitated and cytokines assayed by ELISA/Luminex® assay. IVIG and SCIG both dose-dependently (1-20mg/ml) inhibited (up to >80%) T cell proliferation to anti-CD3 mAb. Response to Candida albicans was comparably inhibited by IVIG and SCIG by 50-80% at 10mg/ml with inhibition even at 3mg/ml (P<0.05). These effects were not affected by depletion of sialic acid containing IgG using neuraminidase treatment or lectin affinity chromatography. With anti-CD3 or Candida stimulation, IL-1β, IL-2, IL-5, IL-6, IL-13, GMCSF, TNF-α, interferon-γ (with anti-CD3) and IL-17 (with Candida) levels were suppressed by IVIG or SCIG, with no effect on IL-4, IL-10, IL-12, IL-15 or TGFβ. Monocytes or B cells were not required for IgG-induced suppression of proliferation, in fact depletion of monocytes potentiated the IgG-induced inhibition. Reconstitution with monocytes restored the original inhibitory effect. These data show that IVIG (Privigen®) and SCIG (Hizentra™) have comparable inhibitory effects on T cell activation, which do not require sialylation of IgG. Inhibition is independent of monocytes or B cells. There is a potent suppression of multiple effector cytokines. Like IVIG, SCIG therapy is expected to show immunomodulatory activity.

Differences in Anti-Inflammatory Actions of Intravenous Immunoglobulin between Mice and Men: More than Meets the Eye

Intravenous immunoglobulin (IVIg) is a therapeutic preparation of polyspecific human IgGs purified from plasma pooled from thousands of individuals. When administered at a high dose, IVIg inhibits inflammation and has proven efficacy in the treatment of various autoimmune and systemic inflammatory diseases. Importantly, IVIg therapy can ameliorate both auto-antibody-mediated and T-cell mediated immune pathologies. In the last few decades, extensive research in murine disease models has resulted in the elucidation of two novel anti-inflammatory mechanisms-of-action of IVIg: induction of FcγRIIB expression by sialylated Fc, and stimulation of regulatory T cells. Whereas controversial findings in mice studies have recently inspired intense scientific debate regarding the validity of the sialylated Fc-FcγRIIB model, the most fundamental question is whether these anti-inflammatory mechanisms of IVIg are operational in humans treated with IVIg. In this review, we examine the evidence for the involvement of these anti-inflammatory mechanisms in the therapeutic effects of IVIg in humans. We demonstrate that although several elements of both immune-modulatory pathways of IVIg are activated in humans, incorrect extrapolations from mice to men have been made on the molecular and cellular components involved in these cascades that warrant for critical re-evaluation of these anti-inflammatory mechanisms of IVIg in humans.

European consensus proposal for immunoglobulin therapies

The use of immunoglobulin (Ig) preparations (intravenous, IVIg, subcutaneous, SCIg) for replacement and immunomodulation therapy worldwide has tripled in the past 20 years and represents an ever-increasing cost factor for healthcare organizations. The limited access to the starting material of this essential medicinal product is currently the driving force for human plasma collection. Increasing awareness and improved diagnosis of human primary immunodeficiencies and a broadening of immunomodulatory indications are responsible for this development, and on a longer run might lead to plasma supply shortages. Consensus recommendations for the optimal use of Ig in clinical practice, including priority rankings for the most urgent indications, are therefore urgently needed. During a recent meeting in Kreuth, Germany, expert nominees from 36 Council of Europe states, together with colleagues from observer countries and regulatory agencies came up with this consensus statement.

Intravenous immunoglobulin G modulates peripheral blood Th17 and Foxp3(+) regulatory T cells in pregnant women with recurrent pregnancy loss

PROBLEM

Th17 cells and Foxp3(+) regulatory T (Treg) cells have been proposed as new risk factors for recurrent pregnancy loss (RPL). Intravenous immunoglobulin G (IVIG) was reported to modulate various immune cells. In this study, we investigated the effect of IVIG on the levels of Th17 and Treg cells and pregnancy outcome in women with RPL.

METHOD OF STUDY

Thirty-seven pregnant women with RPL were enrolled in this study. All had cellular immune abnormality in preconceptional evaluation. Blood was drawn on the day of IVIG treatment and 1 week later from the study subjects during early pregnancy. The proportions of IL-17(+) and Foxp3(+) T cells were analyzed using flow cytometry.

RESULTS

Study population was divided into four groups (Q1-Q4) based on ascending order of the levels of Th17 and Foxp3(+) T cells. IVIG down-regulated Th17 cells in the highest quartile, Q4 (P = 0.001), and up-regulated CD4(+)  Foxp3(+) T cells in Q1 and Q2 (P = 0.025 and 0.029, respectively). In addition, Th17/CD4(+)  Foxp3(+) T cell ratio decreased in Q4 (P = 0.040). We also found a positive trend between successful pregnancy outcome and CD8(+)  IL-17(+) T cells before IVIG treatment (P = 0.05).

CONCLUSION

Intravenous immunoglobulin G treatment modulated imbalance of Th17 and Foxp3(+) Treg cells in pregnant RPL women with cellular immune abnormality.

Comparable autoantibody serum levels against amyloid- and inflammation-associated proteins in Parkinson's disease patients and controls

Naturally occurring autoantibodies (NAbs) against a number of potentially disease-associated cellular proteins, including Amyloid-beta_1–42 (Abeta_1–42), Alpha-synuclein (Asyn), myelin basic protein (MBP), myelin oligodendrocyte glycoprotein (MOG), and S100 calcium binding protein B (S100B) have been suggested to be associated with neurodegenerative disorders, in particular Alzheimer’s (AD) and Parkinson’s disease (PD). Whereas the (reduced) occurrence of specific NAbs in AD is widely accepted, previous literature examining the relation of these NAb titres between PD patients and controls, as well as comparing these levels with demographic and clinical parameters in PD patients have produced inconsistent findings. We therefore aimed, in a cross-sectional approach, to determine serum titres of the above NAbs in a cohort of 93 PD patients (31 of them demented) and 194 controls. Levels were correlated with demographic and clinical variables, cerebrospinal fluid Abeta_1–42, total tau and phospho-tau levels, as well as with single nucleotide polymorphisms (SNPs) of genes which either have been reported to influence the immune system, the amyloid cascade or the occurrence of PD (ApoE, GSK3B, HLA-DRA, HSPA5, SNCA, and STK39). The investigated NAb titres were neither significantly associated with the occurrence of PD, nor with demographic and clinical parameters, neurodegenerative markers or genetic variables. These results argue against a major potential of blood-borne parameters of the adaptive immune system to serve as trait or state markers in PD.

Patients treated with high-dose intravenous immunoglobulin show selective activation of regulatory T cells

Intravenous immunoglobulin (IVIg) is used to treat autoimmune and systemic inflammatory diseases caused by derailment of humoral and cellular immunity. In this study we investigated whether IVIg treatment can modulate regulatory T cells (Tregs ) in humans in vivo. Blood was collected from IVIg-treated patients with immunodeficiency or autoimmune disease who were treated with low-dose (n = 12) or high-dose (n = 15) IVIg before, immediately after and at 7 days after treatment. Percentages and activation status of circulating CD4(+) CD25(+) forkhead box protein 3 (FoxP3(+)) Tregs and of conventional CD4(+) FoxP3(-) T-helper cells (Tconv) were measured. The suppressive capacity of Tregs purified from blood collected at the time-points indicated was determined in an ex-vivo assay. High-dose, but not low-dose, IVIg treatment enhanced the activation status of circulating Tregs , as shown by increased FoxP3 and human leucocyte antigen D-related (HLA-DR) expression, while numbers of circulating Tregs remained unchanged. The enhanced activation was sustained for at least 7 days after infusion, and the suppressive capacity of purified Tregs was increased from 41 to 70% at day 7 after IVIg treatment. The activation status of Tconv was not affected by IVIg. We conclude that high-dose IVIg treatment activates Tregs selectively and enhances their suppressive function in humans in vivo. This effect may be one of the mechanisms by which IVIg restores imbalanced immune homeostasis in patients with autoimmune and systemic inflammatory disorders.

Modeling pre-existing immunity to adenovirus in rodents: immunological requirements for successful development of a recombinant adenovirus serotype 5-based ebola vaccine

Pre-existing immunity (PEI) to human adenovirus serotype 5 (Ad5) worldwide is the primary limitation to routine clinical use of Ad5-based vectors in immunization platforms. Using systemic and mucosal PEI induction models in rodents (mice and guinea pigs), we assessed the influence of PEI on the type of adaptive immune response elicited by an Ad5-based vaccine for Ebola with respect to immunization route. Splenocytes isolated from vaccinated animals revealed that immunization by the same route in which PEI was induced significantly compromised Ebola Zaire glycoprotein (ZGP)-specific IFN-γ+ CD8+ T cells and ZGP-specific multifunctional CD8+ T cell populations. ZGP-specific IgG1 antibody levels were also significantly reduced and a sharp increase in serum anti-Ad5 neutralizing antibody (NAB) titers were noted following immunization. These immune parameters correlated with poor survival after lethal challenge with rodent-adapted Ebola Zaire virus (ZEBOV). Although the number of IFN-γ+ CD8+ T cells was reduced in animals given the vaccine by a different route from that used for PEI induction, the multifunctional CD8+ T cell response was not compromised. Survival rates in these groups were higher than when PEI was induced by the same route as immunization. These results suggest that antigen-specific multifunctional CD8(+) T cell and Th2 type antibody responses compromised by PEI to Ad5 are required for protection from Ebola. They also illustrate that methods for induction of PEI used in preclinical studies must be carefully evaluated for successful development of novel Ad5-based vaccines.

Polyclonal immunoglobulin G for autoimmune demyelinating nervous system disorders

Demyelinating diseases with presumed autoimmune pathogenesis are characterised by direct or indirect immune-mediated damage to myelin sheaths, which normally surround nerve fibres to ensure proper electrical nerve conduction. Parenteral administration of polyclonal IgG purified from multi-donor human plasma pools may beneficially modulate these misguided immune reactions via several mechanisms that are outlined in this review. Convincing therapeutic evidence from controlled trials now exists for certain disorders of the peripheral nervous system, including Guillain-Barré syndrome, chronic inflammatory demyelinating polyradiculoneuropathy, and multifocal motor neuropathy. In addition, there is evidence for potential therapeutic benefits of IgG in patients with chronic inflammatory demyelinating diseases of the central nervous system, including multiple sclerosis and neuromyelitis optica. This review introduces these disorders, briefly summarises the established treatment options, and discusses therapeutic evidence for the use of polyclonal immunoglobulins with a particular emphasis on recent clinical trials and meta-analyses.

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.