More complex and less understood is the interplay of IVIg with defective B cells of PAD patients

More complex and less understood is the interplay of IVIg with defective B cells of PAD patients. a group of defects characterized by a failure to mount protective antibody responses, including X-linked agammaglobulinemia (XLA) and common variable immune disorders (CVID), and as immunomodulatory treatment with high IVIg doses in patients with inflammatory-autoimmune diseases. IVIg contain a broad spectrum of antibody specificities against microorganism antigens able to opsonize and neutralize microbes and toxins. IVIg also contain functionally relevant natural autoantibodies toward a wide range of self-motifs such as Siglec 9, Fas, and BAFF, together with a wide range of specificities including idiotypes of immunoglobulins, T cell receptor, HLA molecules, and other cell surface molecules of immunological importance such as CD4, CD5, BAFF, Fas, cytokines, cytokine receptors, and chemokine receptors that may participate in regulation of the immune response (1). There are many reports on the various immunological effects of high-dose IVIg treatment in patients with inflammatory diseases. Clearly, the significantly smaller doses of immunoglobulin prescribed to PAD patients for replacement therapy may convey different effects (2). The possible immunomodulatory effect of IVIg administered at replacement dosages on innate and adaptive immune cells in patients with PAD needs to be addressed by detailed studies since the Vilazodone D8 peak plasma IgG level reached in patients on replacement administration is much lower that this peak reached in patients with autoimmune-inflammatory disorders. Moreover,in vitrostudies might not be a suitable system to replicate thein vivoeffects of IVIg. In fact, it is possible that thein vitroeffects of IVIg do not recapitulate thein vivoeffects since many cellular and mediator interactions are lacking when IVIg are addedin vitroto experimental conditions. Moreover,in vivostudies might help to analyze the immunomodulatory short- and long-term effects of immunoglobulin on immune cells and the beneficial effects due to the reduction of the infection-associated immune activation that is likely to occur as a result of immunoglobulin replacement. Several theories have been postulated about the mechanisms through which IVIg preparations exert their immune-regulatory properties at replacement dosages possibly involving different type of cells acting in concert (3). Moreover, the diversity of CVID immunological and clinical phenotype could affect the results of some of the experiments. In addition, the commercial IVIg preparation used to study thein vivoorin vitroeffect should be considered, in that IVIg consist mainly of monomeric IgG, but if a residual amount of dimers is present in the preparation, the biological effects might be different (4). == Polymorphonuclear Neutrophils (PMN) == In response to pathogens, PMN rapidly migrate to the Rabbit Polyclonal to Glucokinase Regulator site of inflammation, release proteolytic enzymes and antimicrobial peptides as well as reactive oxygen species. IVIg might modulate PMN activity by a saturating and an activating/inhibiting effect on PMN FcRs (5). Almost 20 years ago, the first demonstration that IVIg administered at low dosages in patients Vilazodone D8 affected by PAD did not alter neutrophils functions was published (6). Phagocytosis, intracellular bactericidal activity, and chemotaxis of PMN in PAD patients Vilazodone D8 treated at very low dosages (IVIg 200 mg/kg/month) and at alternative dosages (IVIg 600 mg/kg/month) were comparable to those of healthy controls (6). We have recently confirmed these data showing that in CVID and XLA patients, PMN were capablein vivoto perform efficient migration, degranulation, phagocytosis, and oxidative burst at baseline and shortly after IVIg administration (7,8). Moreover, IVIg infusion-administeredin vivoat replacement dosages did not alter the PMN expression of receptors involved in PMN functions, such as CD181, CD66b, CD11b, CD11c, CD16, and Siglec 9 (7,8). In contrast with thein vivodata obtained from CVID and XLA patients infused with IVIg, experiments performed with IVIg addedin vitroon isolated PMN or to whole blood (9) showed that IVIg (125 mg/ml) might affect the overall activity of PMN by (1) inducing apoptosis; (2) decreasing the pro-inflammatory activity; (3) inhibiting or activating PMN degranulation (1015) (Physique1). == Physique 1. == Mechanisms of action of intravenous immunoglobulin (IVIg) on innate (neutrophils, monocytes, and dendritic cells) and adaptive (B and T lymphocytes) immune cells. Effects of IVIg (replacement dosages)(A); effects of IVIg (high dosages)(B). Cell images from Ref. (55). Thus,in vitroexperiments provided conflicting results of immunomodulatory effects on PMN activity.