Development of natural tolerance and induced desensitization in cow’s milk allergy

Cow’s milk allergy (CMA) affects 2–3% of infants. It resolves in the great majority spontaneously during childhood. CMA encompasses a spectrum of clinical and immunologic characteristics. Non‐IgE‐mediated allergy typically resolves earlier than IgE‐mediated allergy. The most documented prognostic characteristic is that intense‐specific IgE response predicts persistence of CMA. Low serum levels of cow’s milk (CM)‐specific IgG4 are also associated with persistent CMA. Natural development of tolerance involves an immunologic shift where Th2 responses diminish, and Th1 as well as T regulatory cell responses strengthen. Accordingly, specific IgE levels decrease and specific IgG4, possibly also IgA, levels increase in serum. Specific oral immunotherapy (OIT) with CM induces desensitization in most cases where spontaneous recovery has not yet occurred. Data on long‐term tolerance induction are still scarce. According to current research data, the immunologic changes induced by OIT resemble those seen during natural development of tolerance.     

Defective tumor necrosis factor-α production in infants with cow’s milk allergy

As an aid to clarifying the role of immune mechanisms in the development of cow’s milk allergy (CMA) in suckling infants, we studied the capacity of peripheral blood mononuclear cells (PBMC) to produce tumor necrosis factor-α (TNF-α) in vitro. The study population consisted of 43 infants, aged 0.12–11.2 months; of these, 31 had challenge-proven cow’s milk allergy manifested with either skin or gastrointestinal symptoms or both. In addition, 12 healthy infants were studied as controls. The spontaneous, unstimulated and mitogen-induced production of TNF-α and interferon-γ (IFN-γ) by isolated peripheral blood leukocytes was evaluated. TNF-α and IFN-γ production of PBMC was significantly lower in infants with cow’s milk allergy than in healthy children. Our results indicate that, in infants with CMA, the function of TNF-α-producing cells is defective. This might disturb the development of oral tolerance and thereby lead to cow’s milk allergy. These results may help to clarify the etiopathology of CMA.     

Gastrointestinal manifestations of cow’s milk protein allergy and gastrointestinal motility

Cow’s milk protein allergy (CMPA) may cause gastrointestinal motility disorders. Symptoms of both conditions overlap and diagnostic tests do not reliably differentiate between both. A decrease of symptoms with an extensive hydrolysate and relapse during challenge is not a proof of allergy, because hydrolysates enhance gastric emptying, a pathophysiologic mechanism of gastro‐oesophageal reflux (GER). Thickened formula reduces regurgitation, and failure to do so suggests CMPA. A thickened extensive hydrolysate may induce more rapid improvement, but does not always differentiate between CMPA and GER. Different hypotheses are discussed: is the overlap between CMPA and functional disorders coincidence, or do both entities present with identical symptoms, or does the fact that symptoms are identical indicates that there is only one entity involved? Studies on the prevention of CMPA focused on ‘at‐risk families’, and resulted in a decrease of CMPA and atopic dermatitis, but did not provide data on the incidence of GER. Conclusion: As long as there are no objective diagnostic tools to separate GER from CMPA, the physician has two options: first treat the most likely diagnosis, and switch if after 2–4 weeks there is no improvement, or treat both conditions with one intervention, what will not result in a diagnosis.     

Predictive factors for the persistence of cow’s milk allergy

Santos A, Dias A, Pinheiro JA. Predictive factors for the persistence of cow’s milk allergy.
Pediatr Allergy Immunol 2010: 21: 1127–1134.
© 2010 John Wiley & Sons A/S Cow’s milk allergy (CMA) is usually transient, but recent studies have shown a later acquisition of tolerance to CM. Our aims were to characterize a population of Portuguese children with CMA and to identify predictive factors for the persistence of this food allergy. Children with CMA observed in our Paediatric Allergy Clinic between 1997 and 2006 were selected. Demographic and clinical data were collected from medical records. The group of children who tolerated CM before the age of 2 was compared with the group of children who tolerated CM beyond that age or persisted with CMA until the end of the study. Multivariate logistic regression analysis was used to investigate independent predictive factors for the persistence of CMA beyond the age of 2. In the subgroup of children with IgE‐mediated CMA, the acquisition of tolerance was analysed using Cox regression. In this population of 139 children, the majority presented more than one symptom (73%) affecting more than one organ (51%), with cutaneous (81%), gastrointestinal (55%), respiratory (16%) manifestations and/or anaphylaxis (3%). Thirty‐two per cent developed asthma, 20% atopic eczema, 20% rhinoconjunctivitis and 19% other food allergies over time. The acquisition of tolerance was different in the whole population versus the subgroup with IgE‐mediated CMA: 34%versus 0% at the age of 2, 55%versus 22% at the age of 5 and 68%versus 43% at the age of 10. Immediate allergic symptoms, asthma and other food allergies were independent factors for the persistence of CMA beyond the age of 2. Higher maximum weal diameter on skin prick test to CM and higher maximum level of specific IgE to CM were associated with reduced likelihood of acquiring tolerance in the subgroup of children with IgE‐mediated CMA. In conclusion, children with IgE‐mediated CMA acquire tolerance to CM at older age. Clinical parameters and allergy tests may be helpful in defining prognosis. CM‐allergic children tend to develop other atopic conditions and need specialized follow‐up in the long term.