OBJECTIVEThe incidence of food allergy has increased in recent years and there is no effective way to treat it except strict dietary avoidance and rapid medical treatment in case of accidental exposure. Oral tolerance, as a new method, has shown great promise as an alternative approach to prevention and treatment for allergic disease. It was reported that all-trans retinoic acid (atRA) plays an important role in inducing oral tolerance in vitro. Our study aimed to investigate the immunological effect of different doses of atRA on ovalbumin (OVA) allergic BALB/c mice.

METHODBALB/c mice were sensitized by intraperitoneal injection with OVA to establish allergic animal model. According to the dose of atRA given, 40 OVA allergic BALB/c mice were divided into 4 groups: the mice in high dose group were treated with 100 mg/kg atRA (atRA-H), those in median dose group were treated with 50 mg/kg atRA (atRA-M), those in low dose group were treated with 20 mg/kg atRA (atRA-L) and the mice in control group were given vehicle-soy oil only (CTR). After 12 days of atRA intervention, weight was measured, the mice were checked for diarrhea , and intestinal histology was observed after hematoxylin and eosin staining. The level of OVA-IgE in serum, total IgA and OVA-IgA in feces were measured by ELISA. The percentage of CD4⁺ CD25⁺ FoxP3⁺ T cells in CD4⁺ T cells in mesenteric lymph node was detected by flow cytometry.

RESULTCompared with that of CTR group, the level of OVA-IgE in serum (1.221 ± 0.367 vs. 0.793 ± 0.616) and OVA-IgA (1.573 ± 0.656 vs. 0.905 ± 0.279) in feces decreased significantly (P = 0.006 and 0.012, respectively) without weight and intestinal histology changes after low dose of atRA administration. However, there was no significant difference in the percentage of CD4⁺ CD25⁺ FoxP3⁺ T cells in CD4⁺ T cells in mesenteric lymph node (10.641 ± 1.218 vs. 10.936 ± 0.954) between atRA-L and CTR group (P > 0.05). While in animals with high and median dose of atRA administration, no immunologic improvement was found, instead, there was weight loss and intestinal mucosal damage.

CONCLUSIONLow dose of atRA intervention seems to induce immune suppression in vivo resulting in positive effects on OVA allergic mice. However, median and high dose atRA had no therapeutic effect on OVA allergic mice.