Immune responses to novel allergens and modulation of inflammation by vitamin K3 analogue: A ROS dependent mechanism

The possibility of newer allergens being responsible for atopy needs to be explored at regional level due to environmental variables. Current studies were undertaken to identify common environmental allergens causing atopy in a defined population of India and to correlate the presence of various risk factors with the clinical presentation of allergy. Newer allergens like human dander and rice grain dust were identified and reported as the most common cause of atopy in this region. Atopy, elevated serum total IgE and familial tendency, was observed in 88%, 69% and 58% of allergic patients respectively. Further, allergen-specific immune responses like lymphocyte proliferation and cytokine secretion were studied in vitro using peripheral blood mononuclear cells (PBMC) isolated from both allergic and non-allergic individuals. Although, some allergens induced significant lymphocyte proliferation in vitro, allergen-induced cytokine secretion except that of TNF-α was not seen. Significantly higher ratio of secreted IL-4/IFN-γ cytokines was observed in PBMC isolated from allergic subjects in response to PHA. Plumbagin (vitamin K3 analogue) completely inhibited PHA-induced cytokine production in PBMC, in both allergic and non-allergic individuals. Plumbagin modulated the levels of intracellular reactive oxygen species and glutathione and suppressed PHA induced activation of NF-κB in human PBMC. The results thus show in human PMBC, for the first time, the anti-allergic and anti-inflammatory effects of plumbagin and underscore its therapeutic potential.