Dietary ribonucleotides modulate type 1 and type 2 T-helper cell responsesagainst ovalbumin in young BALB/cJ mice

Dietary ribonucleotides have been shown to augment type 1 T-helper cell (Th 1) responses to a protein antigen (Ag) in Th1-prone C57BL/6 mice, but their effects on type 2 Th (Th2)-prone mice are unknown. BALB/cJ mice have skewe d Th2 responses against ovalbumin (OVA), characterized by augmented product ion of Th2 cytokines and immunoglobulin (Ig)G1/lgE antibodies (Ab); Th1 res ponses augment IgG2a Ab production, whereas Th2 responses augment IgG1/lgE Ab production. In this study, we determined the effects of dietary ribonucl eotides obtained from yeast on the balance of Th1/Th2 responses against OVA in young BALB/cJ mice. Mice were fed a ribonucleotide-free (NF) or ribonuc leotide-supplemented (NS) diet (4.74 g nucleotides/kg diet) and given OVA ( 10 mug/dose) with incomplete Freund's adjuvant (IFA) at 3 and 6 wk. We asse ssed T-cell responses in the regional draining lymph nodes (LN) by measurin g production and expression of Th1/Th2 cytokines, interferon-gamma (IFN-gam ma) and interleukin-5 (IL-5), respectively. Anti-OVA IgG subclass and IgE A b levels were determined 3 wk after the first OVA challenge and 5 d and 2 w k after the second OVA challenge. Dietary ribonucleotides significantly aug mented OVA-specific lFN-gamma production by the regional draining LN cells after the first and second OVA challenges. The NS diet increased anti-OVA I gG2a Ab levels after the first OVA challenge and both anti-OVA IgG2a and an ti-OVA IgG2b after the second challenge, OVA-specific IgG1 and IgE Ab level s were lower (P < 0.05) after the second OVA challenge in mice fed the NS d iet. Dietary ribonucleotides did not affect production or expression of IL- 5. Our findings thus indicate that in Th2-prone BALB/c J mice, dietary ribo nucleotides modulated skewed Th2 responses against OVA toward Th1 as measur ed by production of IFN-<gamma>, a Th1 cytokine, and changes in anti-OVA Ab isotype levels.