Presented at:
Collegium Internationale Allergologicum
Malta, May 5-10, 2006
Time-course analysis of a Double-Blind Placebo Controlled Trail of Grass Pollen Immunotherapy: increased cellular IL-10 production and reduction in late phase responses precede increased IgG4 and early phase responses
Francis JN, Wilcock LK, Paraskavopoulos G, Till SJ, Durham SR
Upper Respiratory Medicine, Allergy and Clinical Immunology, National Heart and Lung Institute, Imperial College, London, UK
Rationale: Mechanisms associated with grass pollen immunotherapy include the induction of IL-10 producing ‘regulatory cells’ and the induction of inhibitory IgG antibodies. This study aimed to establish the time-course of clinical, cellular and humoral responses during a double-blind placebo controlled trial of grass pollen immunotherapy.
Methods: Blood was obtained before and two weekly during a 6-8 week updosing ‘cluster’ regimen of grass pollen immunotherapy (Alutard SQ Phleum Pratense) and thereafter monthly/quarterly during 12 months maintenance injections. Serum allergen-specific (Phleum pratense) IgG4 was measured by ELISA. Flow cytometry was used to detect serum inhibitory activity for IgE-facilitated CD23-dependent allergen binding to B-cells. Allergen-driven IL-10 was assessed by ELISA of PBMC culture supernatants at 6 days. Early and late phase skin responses at 8 and 24 hours respectively after intra-dermal allergen (10BU, Phleum pratense) provided a clinical readout of tolerance induction.
Results: Overall, we observed significant differences between placebo and active groups of increased IL-10 production (p=0.00), decreased early and late phase responses (p=0.00, p=0.00), increased IgG4 production and inhibition of IgE-facilitated allergen binding to B cells (p=0.00). In the active group, the reduction in late skin responses occurred within 2 weeks (p=0.009) which corresponded to the time-course of increased IL-10 production from allergen stimulated PBMC (p=0.001). These changes occurred at low allergen doses (approximately 3,300 SQ, compared to monthly maintenance 100,000 SQ injections). Increases in IgG4 (p=0.01) and in IgG serum inhibitory activity (p=0.001) occurred later, at 4-6 weeks after commencing treatment. Early phase responses were significantly different at similar
Conclusion: The appearance of regulatory mechanisms during grass pollen immunotherapy occurs as early as 2 weeks during the updosing phase. IL-10, a cellular marker of tolerance, precedes increases in IgG4 production and IgG-associated serum inhibitory activity. Early production of IL-10 may therefore make an important contribution to the induction of humoral tolerance during immunotherapy.