The mice, aged three to four weeks, were fed either a control diet containing 15% casein as a protein source or an experimental diet containing 15% of a mixture of amino acids at the same proportion found in casein.
All other nutrients in the two diets were equivalent. This diet continued until the mice reached adulthood at about eight weeks.
Egg (crystallised hen egg albumin) was used as an antigen – an antibody generator. Oral tolerance - a state of systemic suppression of specific immune responses to the antigen – was tested.
The researchers from the Federal University of Minas Gerais and the Federal University of Ouro Preto in Brazil found several alterations of the immune system which could explain this difference to food allergy and oral tolerance.
The amino acid group had lower levels of serum immunoglobulin (Ig) – an antibody – and reduced production of secretory IgA – which plays a critical role in mucosal immunity.
They also found that the intestinal villous (finger-like protrusions from the epithelial lining of the intestinal wall that diffuse digested nutrients) were elongated in the amino acid group their mesenteric lymph nodes cells had a reduced ability to produce cytokines – small proteins important to cell signalling and immune response and inflammation – in the amino acid group compared to the casein protein control group.
Source: British Journal of Nutrition
Published online ahead of print, doi:10.1017/S0007114515000173
“Effect of a protein-free diet in the development of food allergy and oral tolerance in BALB/c mice”
Authors: J. Paula-Silva, A. Fernanda Santiago, R. Pires Oliveira, M. Luciana Paula Rosa , C. Rocha Carvalho, J. Ferreira Amaral and A. Maria Caetano Faria