A flavonoid sulfate antigen activates human alpha beta CD8(+) Th2 lymphocytes in pollen allergy

Cellular immune responses are initiated when T lymphocytes expressing alpha beta TCR recognize peptide antigens bound to MHC molecules or, less freque ntly, double-stranded glycolipid antigens bound to CD1 molecules. In the al lergy to Parietaria judaica, human alpha beta CD8(+) Th2 lymphocytes react to a non-peptide pollinic antigen presented by B cells. The environmental a llergen was purified and identified as a new flavonoid pigment: 2'-O-sulfat e, 6-O-beta D-glucuronopyranosyl, 2',5,6-trihydroxy-isoflavone. Its specifi c recognition by alpha beta CD8(+) Th2 T cells (1) depends upon an MHC- and CD1-independent presentation mediated by B cells, (2) is determined by the flavonoid carbohydrate and sulfate groups and (3) leads to positive skin p rick test in allergic patients. Hence, an unusual mode of aromatic sulfated antigen recognition by alpha beta CD8(+) Th2 T lymphocytes might underlie the cellular mediation of human allergy to plant allergens.