Figure 1
Hypothetical model of a T H 2 dominated adoptive immune response and local T H 2 promoting micromilieu induced by pollen-associated lipid mediators. When pollen grains are hydrated on the respiratory epithelia, they release allergens and eicosanoid lipids, the so-called pollen-associated lipid mediators (PALMs). Leucotrien-like PALMs have the potential to attract and activate innate cells like neutrophils and eosinophils, while prostaglandin-like PALMs, the phytoprostanes, and possibly other pollen-derived factors, can modulate the migratory and T helper cell polarizing capacities of resident dendritic cells. In addition, DCs exposed to PALMs might be induced to secrete chemokines which preferentially recruit further TH2 cells to the site of pollen exposure. Taken together, the possible effects of PALMs on both cells of the innate and the adoptive immune system might lead to a local microenvironment favoring TH2 responses. I FN-γ = interferon-γ; IL = interleukin; PC = plasma cell