Modulation of alloimmune response in vitro by an IgM-enriched immunoglobulin preparation (Pentaglobin)

The mode of action of intravenous immunoglobulins (IVIG) in autoimmune and immunoregulatory disorders is still poorly understood. In vitro, direct effects of IVIG on cytokine release and on cytokine receptors have been described, as well as naturally occurring, neutralizing anticytokine antibodies. The aim of our study was to investigate whether the enrichment in IgM and IgA would have any impact on the in vitro immunomodilatory capacity of IVIG. The preparation tested (Pentaglobin) contains 76% IgG and 12% IgM and IgA, respectively. We could demonstrate a significant inhibition of alloantigen-induced proliferation in the mixed lymphocyte reaction (MLR) even at a Pentaglobin concentration of 1.0 mg/ml. About 10-fold higher concentrations of standard 7S IVIG containing only trace amounts of IgM and IgA were necessary to achieve equivalent suppression of the alloimmune response. Similarly, phytohaemagglutinin (PHA)-induced lymphocyte proliferation was more effectively inhibited by Pentaglobin than by standard 7S IVIG. Cytokine analyses in culture supernatants of MLR provide evidence that Pentaglobin not only modulates interleukin-2 (IL-2), which has already been observed with standard 7S IVIG, but, moreover, modulates interferon-gamma production with a subsequent impact on monocyte-derived tumour necrosis factor-alpha and IL-6 release. Based on these results we conclude that in vitro the IgM- and IgA-enriched Pentaglobin has a more potent immunomodulatory capacity than conventionally used standard 7S IVIG.