Intravenous immunoglobulin replacement treatment reduces in vivo elastase secretion in patients with common variable immune disorders

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.

Persistent Activation of Innate Immunity in Patients with Primary Antibody Deficiencies

Primary antibody deficiencies (PAD) represent a heterogeneous group of disorders, with common variable immunodeficiency being the most common with clinical significance. The main phenotypic defect resides in the inability of B cells to produce antibodies, and the cornerstone of therapy is immunoglobulin replacement treatment in order to fight infections. However, the management of the other inflammatory manifestations is inadequate, reinforcing the hypothesis that a complex genetic background affecting additional cell populations, such as polymorphonuclear cells (PMN) and monocytes, influences the expression of the clinical phenotype of the disease. In this study, we investigated by flow cytometry in different conditions (resting state, and after isolation and incubation, with and without stimuli) the expression pattern of several markers on PMN and monocytes, indicative of their maturation, capacity for chemotaxis, adhesion, opsonization, migration, and phagocytosis in 25 PAD patients, 12 healthy blood donors, and 4 septic patients. In this context, we also analyzed patients before and after the initiation of replacement treatment, as well as an untreated patient in different clinical conditions. Interestingly, we observed that PAD patients exhibit a chronic activation status of the innate immunity compartment, along with several differences in the expression of activation, maturation, and adhesion markers, with respect to different clinical conditions. Moreover, immunoglobulin replacement treatment had a favorable effect on PMN, as it was expressed by a more mature and less activated phenotype on basal state cells, and an enhanced activation capacity after LPS exposure. Thus, we conclude that PAD patients display a persistent innate immune cell activation, which is probably associated with the chronic inflammatory stress, usually observed in these disorders.

Common variable immunodeficiency patients display elevated plasma levels of granulocyte activation markers elastase and myeloperoxidase

Common variable immunodeficiency disorders (CVIDs) represent a group of primary immunodeficiency diseases characterized by hypogammaglobulinemia and dysfunctional immune response to invading pathogens. Previous studies have indicated that CVID is associated with microbial translocation and systemic myeloid cell activation.

The goal of this study was to determine whether patients with CVID display elevated systemic levels of markers of granulocyte activation and whether the levels are further influenced by intravenous immunoglobulin (IVIg) infusions. The plasma levels of granulocyte activation markers elastase and myeloperoxidase were determined using enzyme-linked immunosorbent assay (ELISA) in 46 CVID patients and 44 healthy controls. All CVID patients were in a stable state with no apparent acute infection. In addition, granulocyte activation markers’ plasma levels in 24 CVID patients were determined prior to and 1 h following IVIg administration. Neutrophil elastase and myeloperoxidase plasma levels were significantly higher in CVID patients than in healthy controls. Systemic elastase levels were further increased following IVIg administration. In vitro stimulation of 13 CVID patients’ whole blood using IVIg in a therapeutically relevant dose for 2 h resulted in a significant increase in plasma elastase levels compared to unstimulated blood. The data presented here indicate that CVID is associated with chronic granulocytic activation which is further exacerbated by administering IVIg. Increased myeloperoxidase and elastase levels may contribute to associated comorbidities in CVID patients.