Immune moldulatory effects of intravenous immunoglobulin in vitro and after allogeneic bone marrow transplantation

Abstract: Intravenous immunoglobulin (IVIG) has been used in patients with immunodeficienciesand various autoimmune diseases. Its immune modulatory effect is well documented.In allogeneic bone marrow transplantation (BMT) IVIG has been used to reduce theincidence of infections and graft-versus-host-disease (GVHD). To investigate furtherthe immune-modulatory effects of IVIG, we have studied now its effects on nonspecific(mitogenic) and specific Iymphocyte responses as well as immunoglobulin (Ig) -producingcells. There was a significant dose-dependent inhibition by IVIG of various mitogenic responsesby peripheral blood Iymphocytes (PBL). Inhibition was the same when stimulating differentT-lymphocyte subsets. The specific Iymphocyte response in mixed Iymphocyte cultures(MLC) and to Staphylococcus aureus protein A (SPA) were also inhibited by IVIG. Whencomparing 12 commercial IVIG preparauons (2.5 g/l), inhibition varied from 0% to66%. IgG preparations made from single donors proved more effective than commercialIVIG in inhibiting phytohemagglutinin stimulation. The use of cytomegalovirus (CMV)hyper-Ig compared to IVIG did not result in increased inhibition of the Iymphocyteresponse to herpes virus antigen, but CMV negative Ig resulted in less inhibition.IgG- and IgM-production from PBL and bone marrow cells, measured as plaque-formingcells (PFC) were also inhibited in a dose-dependent fashion by IVIG. Cells were stimulatedby SPA, lipopolysaccharide from E. coli (LPS) or with CMV Antigen (Ag). The inhibitionof spleen-PFC varied depending on the stimuli. We compared equimolar concentrationsof IgG, IgG-F(ab' )2 and IgG-Fc to determine the part of the IgG molecule which mediatedthe inhibitory effect. Lymphocyte responses were inhibited by F(ab')2 fragments,but only by one of two Fc preparations tested. A comparison of 4 brands of IVIG fragmentsshowed that IgG and F(ab' )2 preparauons inhibited IgG and IgM production of LPS-stimulatedspleen cells, but no significant inhibition was obtained with any of the purifiedFc products. In an analysis of serum levels of various cytokines in sibling BMT recipients,we found a correlation between IVIG treatment and decreased serum levels of i) sIL-2r,IL-3, IL-4, IL-6 and IL-10 in patients without complications and ii) IL-lra and TNF-alevels in patients with acute GVHD. In two clinical studies, we evaluated the effects of prophylactic IVIG treatmentafter BMT (0.5 g/kg once weekly until day 90). The 1st study included 98 HLA-identicalsibling transplant recipients and the 2nd 107 recipients of marrow from matched unrelateddonors (MUD). No beneficial effects of IVIG treatment on GVHD, various bacterial,fungal and viral infections or other transplant related complications were detectedin either of the two studies. Of all 208 pauents, only one IVIG-treated patient and4 of the controls had CMV pneumonia. The overall survival rates in the two studieswere similar, with an actuarial two-year survival of 59% in the IVIG group and 57%in the controls. The median follow-up (June, 1997) was 4.4 years and 4.2 years inthe two groups respectively. Forty-two IVIG-treated patients (45%) and 50 controlshave died (45%). Relapse caused the death of 15 treated patients and 16 controls.Fewer IVIG treated pauents died of bacterial infections (2 vs. 11, P=0.03) and moreof the them, died of VOD (7 vs 0, P=0.03). Conclusions: IVIG clearly inhibits cell-mediated T and B cell responsesin vitro. The inhibition seems to be mediated by the F(ab')2 part of the IgG molecule.Immune modulatory effects by IVIG may be beneficial in BMT recipients, but our retrospectivestudy on prophylactic use after HLA identical sibling BMT did not confirm earlierresults about infections and GVHD. Nor did we detect any beneficial effects of treatmentin MUD-transplant reapients. We question the use of prophylactic high-dose IVIG ona regular basis in BMT recipients. Key words: IVIG, IgG, F(ab')2, Fc, immune modulation, T cell responses, Bcell responses, cytokines, bone marrow transplantation, infections, CMV, graft-versus-hostdisease ISBN 91-628-2636-0