Immune defense to dietary cow milk in healthy infants.

The healthy young infant is immunologically adapted to receiving vast amounts of antigens in diet. At the age of 6 months, nine infants were put on a CM elimination diet for 3 weeks and then challenged with CM. Gut immune response was evaluated indirectly with ELISPOT assay at 6 months, after CM elimination (Day 1) and challenge (Day 8), and at 11 months. CM elimination decreased the numbers of immunoglobulin secreting cells (ISC): in the IgM class from mean [95% CI] 4969 [2555, 9653] at 6 months to 1716 [1024, 2873]/10(6) cells on Day 1 (t = 3.14, p = 0.01); and in the IgG class from 5547 [3562, 8630] to 2684 [1383, 5208]/10(6) cells (t = 3.29, p = 0.01). CM challenge further reduced inter-individual variation, and at 11 months the scatter of ISC was comparable to that at 6 months. Specific antibody-secreting cells of the IgA and IgG class were seen at 6 months and again at 11 months, while specific IgM-secreting cells persisted throughout the dietary manipulation. The results indicate that diet profoundly affects the immune defense system, and further suggest that a focused immune response is vital in acquisition of tolerance to dietary antigens.