Combined Supplementation with Arachidonic and Docosahexaenoic Acids in T Helper Type-2 Skewed Brown Norway Rat Offspring is Beneficial in the Induction of Oral Tolerance toward Ovalbumin and Immune System Development

Abstract

Background: A T helper type-2 (Th2) skewed immune response is associated with food allergies. DHA and arachidonic acid (ARA) have been shown to promote oral tolerance (OT) in healthy rodents.

Objectives: We studied the effect of combined ARA + DHA supplementation during the suckling and weaning periods on OT and immune system development in Th2-skewed Brown Norway rat offspring.

Methods: Dams were fed ARA + DHA (0.45% ARA, 0.8% DHA wt/wt of total fat; n = 10) as a suckling period diet (SPD) or control SPD (0% ARA, 0% DHA, n = 8). At 3 wk, offspring from each SPD group received ARA + DHA (0.5% ARA, 0.5% DHA wt/wt of total fat) weaning diet (WD), or control until 8 wk. For OT, offspring were orally exposed to either ovalbumin (OVA) or placebo between 21 and 25 d, followed by systemic immunization with OVA + adjuvant at 7 wk. Primary outcomes, ex vivo cytokine production by splenocytes and plasma OVA-specific Igs, were analyzed using a 3-way ANOVA.

Results: At 8 wk, despite no lasting effect of SPD on splenocytes fatty acids, ARA + DHA WD resulted in 2× higher DHA in splenocyte phospholipid compositions without affecting ARA. OT development was observed in OVA-exposed groups with 15% lower plasma OVA-IgE (P = 0.04) and 35% lower OVA-IgG1 (P = 0.01) than placebo. ARA + DHA SPD resulted in 35% lower OVA-IgG1 and iIL-6 (P = 0.04) when stimulated with LPS, and a higher proportion of mature B cells (OX12+, P = 0.0004, and IgG+, P = 0.008). ARA + DHA WD resulted in 20% higher Th1 cytokines (TNF-α and IFN-γ) production to lymphocyte stimulant and higher splenocyte proportion of CD45RA+ (pan-B cells) and OX6+ (dendritic cells) than control WD (P values < 0.05).

Conclusions: Combined supplementation of ARA and DHA is beneficial for OT development, especially in the suckling period. Further, ARA + DHA supplementation can also counteract the Th2-skewed immunity of Brown Norway rat offspring through higher Th1 cytokine production by lymphocytes.

Keywords: arachidonic acid; docosahexaenoic acid; food allergy; immune system development; mucosal tolerance; nutritional immunology; omega 3; ovalbumin; suckling period; weaning period.