Enzymatic activity of soluble phospholipase A2 does not affect the specific IgE, IgG4 and cytokine responses in bee sting allergy.

Abstract

The soluble bee venom phospholipase A2 (PLA) represents the major allergen/antigen for allergic and hyperimmune individuals following bee sting. A number of studies implicate enzymes, and PLA in particular, as potent allergens. We have studied specific activation of T cells by enzymatically active and inactive mutants of PLA, and secretion of cytokines regulating IgE and IgG4 antibody formation. Recombinant (r) wild type PLA (rPLA-WT) and an enzymatically inactive rPLA (rPLA-H34Q) were produced in Escherichia coli. Eleven bee venom allergic patients and three hyperimmune, healthy individuals were included in the study. After specific stimulation of PBMC with the rPLA variants, proliferative response, IFNgamma, IL-2, IL-4, IL-5, and IL-13 production, as well as total and PLA-specific IgE and IgG4 production, were analysed. Similar levels of specific B cell recognition, proliferative and cytokine responses were observed after stimulation with either enzymatically active or inactive rPLA. In addition, equal amounts of antigen-specific and total IgE and IgG4 antibodies were produced by stimulation with both forms of rPLA. The enzymatic activity of PLA does not influence the specific activation and cytokine production by T cells from bee venom-sensitized or hyperimmune individuals, or the IgE/IgG4 antibodies synthesis by B cells in vitro.