Dietary nucleotides modulate antigen-specific type 1 and type 2 T-cell responses in young C57BL/6 mice

Mice fed a nucleotide-free (NF) diet have impaired antibody (Ab) responses. The mechanisms responsible for this effect are not understood but may be related to specific changes in T-cell functions. The objective of this study was to examine the effects of dietary nucleotides on serum immunoglobulin-G (IgG) subclass Ab levels and T-cell cytokine production by cells from the lymph nodes draining the site of antigen challenge. C57BL/6 (B6) mice were fed an NF diet or the same diet supplemented with nucleotides (NS diet; 4.74 g nucleotides/kg). Keyhole limpet hemocyanin (KLH; 25 mu g/dose), a T-dependent protein neoantigen. was given with incomplete Freund's adjuvant. We administered KLH at 3, 6, and 9 ak to determine primary and secondary responses. Anti-KLH IgG subclass Ab levels were measured 3 wk after the first KLH challenge and 2 wk after the last KLH challenge. T-cell responses in lymph nodes draining the site of KLH challenge were assessed 5 d after the primary and 14 d after the final KLH challenge. We measured mRNA expression and production of interferon-gamma and interleukin-5, type-1 and type-2 T-cell cytokines, respectively. Anti-KLH IgG2a and IgG2b Ab levels were higher in the NS diet group than in the NF diet group after the last KLH challenge. The NS diet group had higher interferon-gamma production and mRNA expression than did the NF diet group after the first KLH challenge. Because increased levels of interferon-gamma and IgG2a/IgG2b Ab reflect a shift toward type-1 responses to antigen stimuli, our results show that dietary nucleotides preferentially enhance type-1 responses to KLH given with incomplete Freund's adjuvant. Nutrition 2000;16:442-446. (C)Elsevier Science Inc. 2000.