Intravenous immunoglobulin induces IgG internalization by tolerogenic myeloid dendritic cells that secrete IL-10 and expand Fc-specific regulatory T cells

Effects of Intravenous Immunoglobulins on Human Innate Immune Cells: Collegium Internationale Allergologicum Update 2024

BACKGROUND

Intravenous immunoglobulin (IVIg) has been used for almost 40 years in the treatment of autoimmune and systemic inflammatory diseases. Numerous cells are involved in the innate immune response, including monocytes/macrophages, neutrophils, dendritic cells, mast cells, basophils, eosinophils, natural killer cells, and innate lymphoid cells. Many studies have investigated the mechanisms by which IVIg down-modulates inflammatory and autoimmune processes of innate immune cells. However, questions remain regarding the precise mechanism of action in autoimmune or inflammatory conditions. The aim of this work was to review the immunomodulatory effect of IVIg on only human innate immune cells. A narrative review approach was chosen to summarize key evidence on the immunomodulatory effects of commercially available and unmodified IVIg on human innate immune cells.

SUMMARY

Numerous different immunomodulatory effects of IVIg have been reported, with some very different effects depending on the immune cell type and disease. Several limitations of the different studies were identified. Of the 77 studies identified and reviewed, 29 (37.7%) dealt with autoimmune or inflammatory diseases. Otherwise, the immunomodulatory effects of IVIg were studied only in healthy donors using an in vitro experimental approach. Some of the documented effects showed disease-specific effects, such as in Kawasaki disease. Various methodological limitations have also been identified that may reduce the validity of some studies.

KEY MESSAGE

As further insights have been gained into the various inflammatory cascades activated in immunological diseases, interesting insights have also been gained into the mechanism of action of IVIg. We are still far from discovering all the immunomodulatory mechanisms of IVIg.

Regulatory dendritic cell therapy in organ transplantation

PURPOSE OF REVIEW

Regulatory dendritic cells (DCregs; also 'tolerogenic DCs'), innate immune cells that regulate the alloimmune response, are a novel cellular therapy for organ transplantation. Preliminary results from early-phase clinical trials in live donor kidney and liver transplantation are promising. This follows many years of research elucidating mechanisms of action and utility of DCregs. Herein, we review early-phase clinical trial observations and recent advances in the production, modification, and future-trajectory of DCreg in organ transplantation.

RECENT FINDINGS

Preclinical work has demonstrated the ability of adoptively transferred DCreg to abrogate ischemia-reperfusion injury and promote long-term allograft survival. Good Manufacturing Practice-grade DCregs have been generated in adequate numbers for early-phase trials of autologous DCregs in kidney transplantation and donor-derived DCreg in liver transplantation. These trials have demonstrated feasibility and safety, with preliminary evidence of an influence on host immune reactivity. In both kidney and liver transplantation, reduced effector CD8 + T-cells have been noted, together with other changes that may be conducive to reduced dependence on immunosuppressive therapy.

SUMMARY

Substantial progress has been made in bringing DCreg to clinical testing in organ transplantation. Additional clinical and mechanistic studies are now needed to further explore and garner the full potential of DCreg in organ transplantation.

Regulatory T cells and cardiovascular diseases

ABSTRACT

Inflammation is a major underlying mechanism in the progression of numerous cardiovascular diseases (CVDs). Regulatory T cells (Tregs) are typical immune regulatory cells with recognized immunosuppressive properties. Despite the immunosuppressive properties, researchers have acknowledged the significance of Tregs in maintaining tissue homeostasis and facilitating repair/regeneration. Previous studies unveiled the heterogeneity of Tregs in the heart and aorta, which expanded in CVDs with unique transcriptional phenotypes and reparative/regenerative function. This review briefly summarizes the functional principles of Tregs, also including the synergistic effect of Tregs and other immune cells in CVDs. We discriminate the roles and therapeutic potential of Tregs in CVDs such as atherosclerosis, hypertension, abdominal arterial aneurysm, pulmonary arterial hypertension, Kawasaki disease, myocarditis, myocardial infarction, and heart failure. Tregs not only exert anti-inflammatory effects but also actively promote myocardial regeneration and vascular repair, maintaining the stability of the local microenvironment. Given that the specific mechanism of Tregs functioning in CVDs remains unclear, we reviewed previous clinical and basic studies and the latest findings on the function and mechanism of Tregs in CVDs.

Serum amyloid A as a biomarker for immunoglobulin resistance in Kawasaki disease

BACKGROUND

Intravenous immunoglobulin (IVIG) resistance is of prime importance in Kawasaki disease (KD). In this study, we examined the value and mechanism of serum amyloid A (SAA) level in predicting IVIG resistance in patients with KD.

METHODS

SAA levels were measured in 497 consecutive patients with KD before IVIG therapy in the training set. The patients were divided into two groups (IVIG-responsive and IVIG-resistant) according to the American Heart Association (AHA) definition of IVIG resistance. Demographic, echocardiographic, and laboratory data were also retrospectively analyzed and tabulated to predict IVIG resistance. The predictive value of SAA was validated on test sets of prospective data. Cytokine microarrays were analyzed from 4 patients with resistant to IVIG, 4 patients with responsive to IVIG and 4 healthy volunteers.

RESULTS

During the training set, 409 patients with KD were enrolled, of whom 43 (10.5%) were resistant to initial IVIG treatment and 47 (11.49%) had coronary artery lesions (CALs). Serum levels of SAA were higher in the IVIG resistant group compared to the IVIG responsive group, (380.00 [204.40-547.25] vs 230.85 [105.40-490.00] mg/L; p = .008). The values of total bilirubin, C-reactive protein, neutrophils, alanine aminotransferase, aspartate aminotransferase, interleukin-6(IL-6), and procalcitonin were significantly higher in the IVIG-resistant group than in the IVIG-responsive group (p < .05); however, the lymphocytes, platelets, serum sodium levels, and duration of fever before IVIG therapy were significantly lower (p < .05). There was no significant difference in SAA levels between patients with KD with and without CALs. Binary logistic regression analysis showed that SAA (p = .008), neutrophils (p < .001), total bilirubin (p = .001), platelet count (p = .004), and serum sodium level (p = .019) were independent factors influencing IVIG resistance. The optimal cutoff value of SAA for IVIG resistance prediction was 252.45 mg/L, with a corresponding clinical sensitivity of 69.8% and specificity of 54.4%. Based on receiver operating characteristic (ROC) curve analyses, the area under the curve (AUC) of combined detection with these five indicators was 0.800, clinical sensitivity was 69.8%, and specificity was 76.2%. In the prospective data, the sensitivity, specificity, and accuracy of SAA for identifying IVIG resistance KD were 77.8%,69.0%, and 70.0%, respectively. Compared with IVIG- responsive group and healthy children, the levels of IL-6 was upregulated significantly in IVIG-resistant group through cytokine microarrays.

CONCLUSIONS

SAA may be a potential biomarker for predicting IVIG responsiveness to KD, Combined detection of SAA levels, total bilirubin, neutrophil count, platelet count, and serum sodium levels is superior to that of any other single indicator for predicting IVIG resistance in KD. And elevated SAA may accompany with IL-6 in KD patients, its use in clinical practice may be helpful for treatment management.

Intravenous Immunoglobulin: Mechanism of Action in Autoimmune and Inflammatory Conditions

Intravenous immunoglobulin (IVIG) is the mainstay of therapy for humoral immune deficiencies and numerous inflammatory disorders. Although the use of IVIG may be supplanted by several targeted therapies to cytokines, the ability of polyclonal normal IgG to act as an effector molecule as well as a regulatory molecule is a clear example of the polyfunctionality of IVIG. This article will address the mechanism of action of IVIG in a number of important conditions that are otherwise resistant to treatment. In this commentary, we will highlight mechanistic studies that shed light on the action of IVIG. This will be approached by identifying effects that are both common and disease-specific, targeting actions that have been demonstrated on cells and processes that represent both innate and adaptive immune responses.

Increased Myosin light chain 9 expression during Kawasaki disease vasculitis

Introduction

Kawasaki disease (KD) is an acute systemic vasculitis that predominantly afflicts children. KD development is known to be associated with an aberrant immune response and abnormal platelet activation, however its etiology is still largely unknown. Myosin light chain 9 (Myl9) is known to regulate cellular contractility of both non-muscle and smooth muscle cells, and can be released from platelets, whereas any relations of Myl9 expression to KD vasculitis have not been examined.

Methods

Plasma Myl9 concentrations in KD patients and children with febrile illness were measured and associated with KD clinical course and prognosis. Myl9 release from platelets in KD patients was also evaluated in vitro. Myl9 expression was determined in coronary arteries from Lactobacillus casei cell wall extract (LCWE)-injected mice that develop experimental KD vasculitis, as well as in cardiac tissues obtained at autopsy from KD patients.

Results and discussion

Plasma Myl9 levels were significantly higher in KD patients during the acute phase compared with healthy controls or patients with other febrile illnesses, declined following IVIG therapy in IVIG-responders but not in non-responders. In vitro, platelets from KD patients released Myl9 independently of thrombin stimulation. In the LCWE-injected mice, Myl9 was detected in cardiac tissue at an early stage before inflammatory cell infiltration was observed. In tissues obtained at autopsy from KD patients, the highest Myl9 expression was observed in thrombi during the acute phase and in the intima and adventitia of coronary arteries during the chronic phase. Thus, our studies show that Myl9 expression is significantly increased during KD vasculitis and that Myl9 levels may be a useful biomarker to estimate inflammation and IVIG responsiveness to KD.

The yin/yang balance of the MHC-self-immunopeptidome

The MHC-self immunopeptidome of professional antigen presenting cells is a cognate ligand for the TCRs expressed on both conventional and thymic-derived natural regulatory T cells. In regulatory T cells, the TCR signaling associated with MHC-peptide recognition induces antigen specific as well as bystander immunosuppression. On the other hand, TCR activation of conventional T cells is associated with protective immunity. As such the peripheral T cell repertoire is populated by a number of T cells with different phenotypes and different TCRs, which can recognize the same MHC-self-peptide complex, resulting in opposite immunological outcomes. This article summarizes what is known about regulatory and conventional T cell recognition of the MHC-self-immunopeptidome at steady state and in inflammatory conditions associated with increased T and B cell self-reactivity, discussing how changes in the MHC-ligandome including epitope copy number and post-translational modifications can tilt the balance toward the expansion of pro-inflammatory or regulatory T cells.

T Cells in Multisystem Inflammatory Syndrome in Children (MIS-C) Have a Predominant CD4+ T Helper Response to SARS-CoV-2 Peptides and Numerous Virus-Specific CD4- CD8- Double-Negative T Cells

We studied SARS-CoV-2-specific T cell responses in 22 subacute MIS-C children enrolled in 2021 and 2022 using peptide pools derived from SARS-CoV-2 spike or nonspike proteins. CD4+ and CD8+ SARS-CoV-2-specific T cells were detected in 5 subjects, CD4+ T helper (Th) responses alone were detected in 12 subjects, and CD8+ cytotoxic T cell (CTL) responses alone were documented in 1 subject. Notably, a sizeable subpopulation of CD4- CD8- double-negative (DN) T cells out of total CD3+ T cells was observed in MIS-C (median: 14.5%; IQR 8.65-25.3) and recognized SARS-CoV-2 peptides. T cells bearing the Vβ21.3 T cell receptor (TcRs), previously reported as pathogenic in the context of MIS-C, were detected in high frequencies, namely, in 2.8% and 3.9% of the CD4+ and CD8+ T cells, respectively. However, Vβ21.3 CD8+ T cells that responded to SARS-CoV-2 peptides were detected in only a single subject, suggesting recognition of nonviral antigens in the majority of subjects. Subjects studied 6-14 months after MIS-C showed T cell epitope spreading, meaning the activation of T cells that recognize more SARS-CoV-2 peptides following the initial expansion of T cells that see immunodominant epitopes. For example, subjects that did not recognize nonspike proteins in the subacute phase of MIS-C showed good Th response to nonspike peptides, and/or CD8+ T cell responses not appreciable before arose over time and could be detected in the 6-14 months' follow-up. The magnitude of the Th and CTL responses also increased over time. In summary, patients with MIS-C associated with acute lymphopenia, a classical feature of MIS-C, showed a physiological response to the virus with a prominent role for virus-specific DN T cells.