Background: Immune responses are often divided into T helper 1 (Th1), Th2 and Treg like immunity. Allergy is associated with Th2 like responses to allergens and possibly to reduced regulatory functions. Activation via the CD2 receptor increases the production of the Th1 associated cytokine IFN-g and enhances the responses of activated T cells to IL-12. This may be due to an up-regulation of the signal-transducing β2-chain of the IL-12 receptor. CD2 function may be impaired in allergic children. As IL-12 is a strong promoter of Th1 like responses, this may be one contributing factor to the Th2-skewed immune responses found in allergic children. IL-27 and its receptor component WSX-1 may also play a role in Th1 like responses. The transcription factors T-bet, GATA-3 and Foxp3 are associated with Th1, Th2 and Treg type of immune responses, respectively.
Aim: To investigate possible mechanisms behind the reduced Th1 and/or Treg associated immunity in relation to allergy by studying the CD2 induced regulation of IL-12Rβ2, WSX-1, T-bet, GATA-3 and Foxp3, as well as the production of different cytokines in children and adults. The aim was also to study the development of these factors during the first two years of life in relation to development of allergy in children from a country with high (Sweden) and low (Estonia) prevalence of allergy.
Material and methods: Four different study groups were included; 32 12-year-old children, 38 7-year-old children, 61 children followed from birth to two years of age and 20 adults. Peripheral blood mononuclear cells were cultured with PHA (which partly signals via CD2), IL-2 and IL-12 alone and in combination or with anti-CD2 alone or combined with anti-CD28 antibodies. mRNA expression of cytokine receptors and transcription factors was analysed with real-time PCR and production of Th1, Th2 and Treg associated cytokines with ELISA.
Results: We found lower PHA-induced IL-12Rβ2 and IFN-γ production in 12-year-old children with positive skin prick tests (SPT), compared with SPT negative children. We also found lower IL-2 induced IL-12Rβ2 in children with allergic airway symptoms and high IgE levels compared to children without a history of allergy and low IgE levels. This was accompanied with lower IL-2 and IL-12 induced IFN-γ. The spontaneous mRNA expression of IL-12Rβ2, WSX-1, T-bet, GATA-3 and Foxp3 was similar at birth and at 24 months. PHA induced up-regulation of all markers at all ages except for GATA-3, which was up-regulated in allergic children only at 6 and 12 months. PHA-induced T-bet and WSX-1 increased from birth to 24 months in non-allergic children. At a specific age, similar levels of all markers were found in allergic and non-allergic children, except for higher spontaneous IL-12Rβ2 at 24 months and higher PHA-induced WSX-1 at birth in allergic children. All cytokines increased with age. No clear differences were found between Swedish and Estonian children. CD2 stimulation induced Foxp3 and IL-10, while CD2 together with CD28 stimulation induced both Th1 and Th2 related transcription factors and cytokines. The combination also hampered the CD2 induced expression of Foxp3.
Conclusions: The CD2 pathway and the response to IL-2 may be impaired in allergic children as lower IL-12Rβ2 and IFN-g were found in allergic, compared to non-allergic children. This difference was not found in adults. CD2 may be involved in induction of regulatory T cell responses as stimulation via CD2 in the absence of other co-stimulatory molecules induced Foxp3 and IL-10. Different developmental patterns of Th1 and Th2 associated factors may influence the development of allergic diseases in childhood.
Institutionen för molekylär och klinisk medicin , 2006.