Milk from cows is consumed by all age groups as an excellent source of high-quality protein and
other nutrients. The β casein which constitutes up to 35% of the total protein in cow milk has
been found to have 13 different genetic variants of which the A1 β casein variant of cow milk
has been associated with higher incidence of diseases like type 1 diabetes, ischaemic heart
disease and neurological disorders such as schizophrenia and autism. The objective of the present
study was to evaluate the role of A1A1, A1A2 or A2A2 β casein variants of cow milk in
modulating HDM induced allergic airway disease in murine model. We found that on inducing
acute allergic airway disease with HDM in mice fed with A1A1, A1A2 and A2A2 milk for 30
weeks, the A1A1 and A1A2 milk fed BALB/c mice had significantly higher airway
hyperresponsiveness as compared to those fed with A2A2 milk. The IL-4 levels in BAL as well
as serum and IL-5 levels in serum were found to be significantly higher in the A1A1 milk fed
mice as compared to those fed with A2A2 milk while the IFN- levels were not affected clearly
indicating Th2 polarization of the immune response. The IgE and IgG levels were significantly higher in BAL as well as serum of mice fed with A1A1 milk as compared to those fed with
A2A2 milk which was also accompanied with significantly increased influx of inflammatory
cells which was mainly due to increase in eosinophils, lymphocytes and neutrophils in BAL and
eosinophils and lymphocytes in blood. Histology of lung tissue sections of mice fed with A1A1
milk also revealed increased airway inflammation, marked collagen tissue deposition and
presence of mucus as compared to other milk groups. Based on these results it is concluded that
the A1A1 β casein variant of cow milk is exacerbating HDM induced allergic airway disease in
murine model.