KETOTIFEN INHIBITS ALLERGEN-SPECIFIC T-LYMPHOCYTES RESPONSES BY SUPPRESSING ANTIGEN PRESENTATION WITH CONCOMITANT DECREASE OF HLA-DQ ANTIGEN ON MACROPHAGES

Allergen activates T lymphocytes responsive to interleukin 2 (IL-2) in allergic patients but not in normal individuals, This response was su ppressed by antiallergic agent, Ketotifen (4-(1-methyl-4-piperidyliden e)-4H-benzo [4, 5] cyclohepta [1, 2-b] thiophen-10 (9H)-one hydrogen ( fumarate). Prolonged culture of antigen-presenting adherent cells impa ired the ability to present Dermatophagoides farinae (Df) antigen to T cells, whereas stimulation of adherent cells with recombinant interfe ron-gamma (IFN-gamma) restored the antigen-presenting capability, The maintained antigen presenting ability of adherent cells treated with I FN-gamma was also suppressed by Ketotifen, Fluorescence activated cell sorter (FAGS) analysis disclosed that Ketotifen selectively reduced t he expression of HLA-DQ antigen, crucial restriction elements in of an tigen-related responses, on macrophages but not on a cells, even in th e presence of IFN-gamma. Collectively, Ketotifen prevented macrophages from inducing allergen-activated T lymphocytes' responsiveness to IL- 2 at least in part by decreasing the expression of HLA-DQ antigen.