Immune modulation and possible pathological implications mediated by naturally produced immunoglobulin G idiotypes: from historical to recent experimental and clinical studies focused on atopic dermatitis.

Since the 1950s decade, it has been suggested that a naturally produced or induced repertoire of immunoglobulin G (IgG) idiotypes may exert some immunoregulatory functions. In the last decades, some more advanced theories have suggested that the repertoire of IgG idiotypes may influence the development or control of some atopic diseases. In atopic dermatitis (AD), some evidence indicated that the IgG repertoire obtained from these patients could effectively mediate regulatory functions on thymic and peripheral CD4+ and CD8+ T cells. Furthermore, some recent clinical trials have corroborated the hypothesis that IgG from AD patients can exert regulatory functions in vivo. Here, we revised some historical aspects that yield current approaches developed in vitro and in vivo to elucidate a recently proposed theory termed "hooks without bait" that can strengthen the broad spectrum of research about evaluating different sets of IgG idiotypes and determine their immunological effects.