Background: Treg cells and dietetic factors may play a significant role in the natural acquisition of tolerance in children with cow’s milk allergy (CMA). The best marker for Treg lymphocytes is the transcription factor forkhead boxP3 (FOXP3).
Objective: We examine the relationship between FOXP3 mRNA expression and serum concentrations of vitamins D and C and the development of different phenotypes of tolerance in children with CMA.
Material and methods: The study group comprised 138 infants with CMA and 101 healthy infants. All children underwent oral food challenge, first with an extensively heated milk product and then with unheated products. FOXP3 mRNA expression and serum vitamin C and D concentrations were evaluated.
Results: At 2 years of life, 54 children (39.1%) still had CMA, 43 (31.2%) were unheated milk–reactive and heated milk–tolerant, while 41 (29.7%) had outgrown their allergy. The mean (SD) level of FOXP3 expression in the study group was 2.07 (1.23), which was lower than the control group value of 2.98 (1.52) (P<.001). A value below 1.45 indicated allergy. The mean serum level of vitamin D in the study group was lower than in the control group (29.67 [7.09] vs 33.35 [4.13] ng/mL; P<.001). No significant differences were found in mean serum vitamin C content.
Conclusions: Increased FOXP3 mRNA expression can predict faster acquisition of tolerance in infants with CMA. These children have lower serum vitamin D levels than healthy children. No relationship was found between the natural history of CMA and serum vitamin C concentration.

Key words: Food allergy, FOXP3, Tolerance, Children, Vitamin D, Vitamin C, Cow’s milk