Peripheral blood mononuclear cell proliferative responses in the first year of life in babies born to allergic parents

Background Raised peripheral blood mononuclear cells (PBMCs) proliferative responses to food allergens have been demonstrated in children with established atopic dermatitis. Objective In this report we investigate the PBMC proliferative responses to inhalant and food allergens from babies at birth, 6 months and 1 year of age, born to atopic and non-atopic parents. Methods PBMCs, separated by density gradient centrifugation. were cultured for 6 days with autologous plasma and a range of allergens (house dust mite [HDM], cat, grass pollen, tree pollen, betalactoglobulin and ovalbumin). Proliferative responses were measured by the uptake of [³H] thymidine added for the final 18 h of culture. Results At birth, infants born to atopic parents who developed allergic disease by 1 year of age had significantly more positive responses (stimulation index ± 2 with a value of ± 1000 cpm above background) to HDM (P = 0.0091), betalactoglobulin (P= 0.0166) and ovalbumin (P = 0.0035) than newborns who did not develop allergy. Tnfants who developed allergy also had significantly more positive responses to HDM (P - 0.03) and ovalbumin (P = 0.0057) than babies, born to non-atopic parents, who did not develop allergies. At 6 months of age a significant fall in response to HDM (P = 0.003) and cat fur extract (P = 0.006) was seen in infants who developed allergic disease by 1 year of age. A similar pattern was seen for proliferative responses to betalactoglobulin and ovalbumin (P = 0.0006. P= 0.004). Conversely, proliferations to grass and tree pollen extracts increased at 6 months (P = 0.04. P = NS) and 1 year (P= NS. P= 0.01) compared with birth which was significant for infants who did not develop allergic disease. Conclusion Proliferative responses to seasonal allergens increased over the first year of life whilst those to perennial allergens, both inhalant and food, fell. This suggests either the induction of a systemic immune tolerance by perennial exposure to antigens or movement of sensitized cells to target organs where allergen exposure occurs. This process may be independent of the development allergic disease.