Activation of human granulocytes by intravenous immunoglobulin preparations is mediated by FcgammaRII and FcgammaRIII receptors.

Previous studies from our laboratory have shown that i.v. Ig (IVIG) exposure triggers superoxide anion (O2) generation by and increases bactericidal capacity of human blood granulocytes. However, the molecular interactions between IVIG and granulocytes have not been evaluated before. The objective of this study was to investigate the role of FcgammaRII and FcgammaRIII receptors in the immunomodulatory effects of IVIG concentrates on granulocytes. We found that four different IVIG preparations (concentration range, 1-10 mg/mL) shared the ability to stimulate O2- release in vitro by granulocytes in a dose-dependent manner. Dimers fractionated from IVIG were significantly more potent in inducing activity of the respiratory burst than were monomers. MAb (concentration range, 0.1-10 microg/mL) specific for FcgammaRII and FcgammaRIII receptors inhibited the IVIG-induced O2- release, with a more profound inhibitory effect observed with anti-FcgammaRIII. These findings suggest the involvement of Fcgamma receptors in triggering O2- release by granulocytes exposed to IVIG. We also report that IVIG added to granulocyte suspensions elicited a rapid and vigorous increase in the concentration of cytosolic free calcium, a finding suggesting direct activation and not priming of granulocytes by IVIG through FcgammaRII and FcgammaRIII receptors. The in vitro effects described here might occur in patients treated with IVIG and may, in part, be responsible for inflammatory reactions evoked by infused Ig concentrates as well as the immunomodulatory effect of Ig in patients with autoimmune and inflammatory diseases.

Antigen-specific and polyclonal immunoglobulin production induced by a cloned tetanus toxoid-specific T cell line.

This report describes the isolation and the phenotypic and functional characterization of a cloned, IL 2 dependent, TT-specific human helper T cell line (TCL), designated 1A1. 1A1 was derived by limiting dilution culture of a bulk IL 2-dependent TCL that was found to contain both TT and trinitrophenyl (TNP) altered self-reactive T cells. Specifically, 1A1 represents the outgrowth of one well of a microwell cloning plate initially seeded at 1 TCL/well, from which less than 4% (3/96) wells grew. Phenotypic analysis, utilizing a battery of monoclonal antibodies, demonstrates that all 1A1 cells are T cells belonging to a stable and discrete T cell subset: T3+, T4+, T17+, T8-. In proliferative assay, 1A1 responds specifically to TT but not to other soluble antigens against which the donor is sensitized, a panel of allogeneic stimulators, nor to TNP-modified-self. Moreover, 1A1 is HLA-DRw-restricted, proliferating only to TT in association with DRw3+ antigen-presenting cells. Of greater interest is the observation that 1A1 is an antigen-specific helper T cell line. Thus, by utilizing ELISA systems to quantitate class-specific immunoglobulin and antigen-specific antibody, it was determined that co-culture of autologous B cells, 1A1 cells, and a low concentration (1 to 10 ng/ml) of TT results in an IgG response that is predominantly, if not exclusively, antigen-specific antibody. In contrast, the presence of high concentrations of TT (4 micrograms/ml) triggers a polyclonal immunoglobulin response comprised of IgM with a small IgG component that is essentially devoid of anti-TT antibody. These results demonstrate that depending on the mechanism of activation, a cloned antigen-specific helper T cell line can mediate antigen-specific or polyclonal help for autologous B cells.