Pollen Lipidomics: Lipid Profiling Exposes a Notable Diversity in 22 Allergenic Pollen and Potential Biomarkers of the Allergic Immune Response

Abstract

Background/AimPollen grains are the male gametophytes that deliver sperm cells to female gametophytes during sexual reproduction of higher plants. Pollen is a major source of aeroallergens and environmental antigens. The pollen coat harbors a plethora of lipids that are required for pollen hydration, germination, and penetration of the stigma by pollen tubes. In addition to proteins, pollen displays a wide array of lipids that interact with the human immune system. Prior searches for pollen allergens have focused on the identification of intracellular allergenic proteins, but have largely overlooked much of the extracellular pollen matrix, a region where the majority of lipid molecules reside. Lipid antigens have attracted attention for their potent immunoregulatory effects. By being in close proximity to allergenic proteins on the pollen surface when they interact with host cells, lipids could modify the antigenic properties of proteins.Methodology/Principal FindingsWe performed a comparative pollen lipid profiling of 22 commonly allergenic plant species by the use of gas chromatography-mass spectroscopy, followed by detailed data mining and statistical analysis. Three experiments compared pollen lipid profiles. We built a database library of the pollen lipids by matching acquired pollen-lipid mass spectra and retention times with the NIST/EPA/NIH mass-spectral library. We detected, identified, and relatively quantified more than 106 lipid molecular species including fatty acids, n-alkanes, fatty alcohols, and sterols. Pollen-derived lipids stimulation up-regulate cytokines expression of dendritic and natural killer T cells co-culture.Conclusions/SignificanceHere we report on a lipidomic analysis of pollen lipids that can serve as a database for identifying potential lipid antigens and/or novel candidate molecules involved in allergy. The database provides a resource that facilitates studies on the role of lipids in the immunopathogenesis of allergy. Pollen lipids vary greatly among allergenic species and contain many molecules that have stimulatory or regulatory effects on immune responses.

Human Invariant Natural Killer T Cells Respond to Antigen-Presenting Cells Exposed to Lipids from Olea europaea Pollen

“…This is in agreement with previous studies in both animal models and human subjects suggesting that iNKT cells might significantly affect the course of asthma or respiratory allergy [13,14,15,16]. …”

Analysis of morphological and molecular composition changes in allergenic Artemisia vulgaris L. pollen under traffic pollution using SEM and FTIR spectroscopy

“…Also, elevated tropospheric ozone concentration results in the decrease of bonds corresponding to glycerolipids (Kanter et al 2013). This finding could have an implication in allergology, when we face unclear pathomechanism and allergy symptoms (Bashir et al 2013). …”

“…Pollen lipids play also an important role in the induction and the strengthening of allergy (Risse et al 2000). They could alter the allergenic properties of proteins and modify the immune response (Bashir et al 2013). Lipids content and their quantitative changes can be easily detected by infrared spectroscopy (Jiang et al 2015).…”

Bacterial membranes enhance the immunogenicity and protective capacity of the surface exposed tick Subolesin-Anaplasma marginale MSP1a chimeric antigen

“…Among the predominant lipid components in the membrane-bound SUB-MSP1a antigen, fatty acids and conjugates (21%), fatty alcohols (7%) and sterols (7%) (Fig. 5A) have been shown to act as adjuvant or have potent immunoregulatory effects (Bomford, 1981;Bashir et al, 2013). Additionally, the ability of bacterial LPS to function as an adjuvant and enhance the immune response to antigens has been well established (Hoogerhout et al, 1995) and this adjuvant activity resides in its lipid A moiety (Han et al, 2014).…”