Desensitization of ovalbumin-sensitized mice by repeated co-administrations of di-(2-ethylhexyl) phthalate and ovalbumin

Compared to the OVA-sensitised control mice, multiple co-exposures to DEHP+OVA reduced the IgG1 level and reduced the IgE/IgG2a ratio. This suggests that DEHP may attenuate allergic sensitisation, as the IgE/IgG2a ratio has been shown to correlate with the degree of anaphylaxis. Nevertheless, no effect of DEHP exposures was seen on inflammatory cells in bronchoalveolar lavage fluid and on cytokine levels in spleen cell culture.Data from humane and murine studies suggest that DEHP may attenuate the allergic response. More studies are necessary in order to assess the size of this effect and to rule out the underlying mechanism.The plastizicer di-(2-ethylhexyl) phthalate (DEHP) is widely distributed in the environment and DEHP is, for example, present in house dust [1], which also contains allergens e.g. from house dust mites. Therefore, the potential allergy-promoting effect of DEHP and other phthalates was evaluated in several recent studies [2]. Although some of the epidemiological studies suggested that phthalates promote allergic sensitisation [3,4], these findings could not be confirmed in controlled animal studies [5-7]. In mice, co-administration of DEHP with the model allergen ovalbumin (OVA) stimulated production of the immunoglobulins IgG1 and IgG2a but not IgE [6,7]. IgE plays a central role in many allergic diseases, whereas the role of IgG1 is less clear. IgG1 is a Th2-dependent antibody that may be anaphylactic in the mouse at high allergen exposures [8,9]. On the other hand, it has been proposed that IgG1 may constitute the murine equivalent to the human IgG4 isotype, which may protect against symptoms of allergy [10]. In mice, decreased IgG1 and increased IgG2a have been associated with the development of mucosal tolerance towards inhaled allergens [11]. If DEHP selectively promote formations of IgG1 and IgG2a without stimulating the IgE response, it could be hypothesized that DEHP may be able to suppress elicitation of an allergic response. This hypot