Introduction: Non-typeable H. influenzae(NTHi) is the most common bacterial pathogen associated with chronic suppurative lung disease (CSLD). Limited data exists regarding the adaptive immune response to NTHi and the role it may have in the aetiology of CSLD in children.
Aim: To determine if children with CSLD have a suboptimal adaptive immune response to NTHi.
Method: NTHi-stimulated cytokine (IFNg, IL-13 and IL-10) production from peripheral blood mononuclear cells (PBMC) were measured in 82 children with CSLD and 51 healthy control children (HC). Plasma antibody titres (IgG1,IgG4) to the H. Influenzae outer membrane proteins P4 and P6 were also measured.
Results: Compared to healthy controls, PBMC from children with CSLD pro-duced significantly more IL-13 (p=0.030) and significantly less IFNg(p<0.001) and IL-10 (p=0.029) in response to NTHi. CSLD was associated with significantly lower P4-specific IgG1 titres but there was no significant difference in P6-specific IgG1 between the two groups. The prevalence of detectable IgG4 to both P4 and P6 was low in both groups however the level of response to P6 was significantly lower in children with CSLD (p<0.001).IL-10 was positively correlated with P4 and P6-specific IgG4 (p=0.022 and p=0.003 respectively).
Conclusion: Cell mediated immunity, in particular the IFNg response, likely plays an important role in protective immunity against NTHi in children. The inability to elicit a strong IFNg response to NTHi may contribute to the patho-genesis of CSLD. Whilst the cell-mediated immune response in CSLD isTH2-skewed (high IL-13, low IFNg), low IL-10 production and low IgG4 titres suggest a more complex form of immune dysregulation in children with CSLD.