Antibodies to specific cell surface antigens of a human leukemia cell line, K-562, transduce negative growth signals

Immunomodulation and remyelination: two aspects of human polyclonal immunoglobulin treatment in immune mediated neuropathies?

Intravenous immunoglobulin is used in inflammatory demyelinating diseases of the peripheral as well as the central nervous system. It is not known which mechanism(s) accounts for the beneficial effect observed in these diseases. The immunomodulatory effects of IVIg in two different models of T and B cell activation were investigated. IVIg inhibited a predominantly cellular immune response of the Th 1 type, which was partially reversed by addition of Th 1 cytokines. In contrast, in a model, which leads to B cell differentiation and antibody production, a synergistic stimulatory effect of IVIg and Th2 cytokines was observed. The ability of IVIg to interfere with cell proliferation and to manipulate the Th1/Th2 profile will have consequences for the induction, character, and amplification of an immune response. Apart from the immunomodulatory effects, evidence shows that IVIg promote remyelination not only by abrogation of the auto-immune attack but also by an effect on glial cells. We showed that IVIg induce growth arrest of normal human fibroblasts and Schwann cells. In fibroblasts this growth arrest is accompanied by upregulation of GAS-3/PMP-22 mRNA. The implications of this finding are discussed. Further studies in human Schwann cells are imperative to prove the hypothesis that IVIg directly stimulates remyelination.

Polyvalent immunoglobulin for intravenous use interferes with cell proliferation in vitro

Intravenous immunoglobulin is used to an increasing extent in various immune-mediated diseases, but its mechanism(s) of action in vivo is incompletely understood. Previous studies have shown that intravenous immunoglobulin may interfere with autoantibodies and their production by B cells and also inhibit Fc-mediated antibody-dependent cytotoxicity. Here we describe a novel effect of intravenous immunoglobulin on proliferation of in vitro activated peripheral blood lymphocytes and autonomously growing cell lines of various origin. Independently of whether proliferation was autonomous or induced by antigen-specific or antigen-nonspecific reagents, proliferation was inhibited in a dose-dependent fashion, as measured by reduced 3H-thymidine and BrdU uptake and cell counting. The effect was not due to cytotoxic effects of intravenous immunoglobulin and was reversible after removing the intravenous immunoglobulin by washing. The IgG levels required for this inhibition of proliferation are supraphysiological but are reached in vivo during treatment with intravenous immunoglobulin.