Impaired maturation of monocyte-derived dendritic cells from birch allergic individuals in association with birch-specific immune responses

• Optimal activation of T lymphocytes requires a costimulatory signal provided by the interaction of molecules on the surface of T cells with their ligands expressed on dendritic cells (DC). We investigated whether DC differentiated from monocytes from healthy and birch allergic asthmatic individuals and further maturated by stimulation with cat and birch allergens and LPS differ in their phenotypic receptor expression. Similar expression of DC surface markers, including HLA-DR, CD80, CD86, CD83, CD1a and CD11c, was detected in monocyte-derived DC from allergic and healthy individuals. Cells from healthy donors stimulated either antigen showed a similar activation of the CD80 and double CD80/CD86 costimulatory molecules when compared with non-stimulated cells. In the case of cells from allergic individuals, birch allergen was unable to produce the same increased expression of CD80 alone or in combination with CD80/CD86, in comparison with cells stimulated with cat and LPS. Levels of IL-6, IL-8, IL-10, MCP-1/MCAF and MIP-1β were similar in the supernatant of non-stimulated DC from both groups of subjects. By contrast, the spontaneous secretion of IL-12p70 and TNF-α was higher in the supernatant of DC from healthy subjects when compared with that from allergic individuals. Stimulation with birch and LPS resulted in an increased secretion of IL-12p70 in samples from healthy when compared with that in allergic individuals. The results suggest an impaired specific maturation of DC from birch allergic individuals in association with birch-specific immune responses. Lower secretion of IL-12p70 from birch-stimulated DC from allergic individuals suggests that not only maturation, but also the specific Th1 function of these cells seems to be affected in those individuals.

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