Lymphocyte stimulation test with drug-photomodified cells in patients withquinolone photosensitivity

Quinolone antibacterial agents, known to elicit photosensitive dermatitis a s an adverse effect, have both phototoxicity and photoallergenicity. The la tter potency is mainly derived from their photohaptenic moiety; quinolones covalently bind to protein and cells upon exposure to ultraviolet A (UVA) l ight. Our previous study has shown the in vivo and in vitro antigenicity of quinolone-photomodified cells in mice. Here, we examined the presence of s ensitized lymphocytes that react with quinolone-photomodified autologous ce lls in patients with photosensitivity to quinolones. A flow cytometric anal ysis using a monoclonal antibody specific to quinolone photoadducts demonst rated that peripheral blood mononuclear cells (PBMC) were successfully phot omodified with quinolones upon exposure to UVA. PBMC from quinolone-photose nsitive patients were cocultured with autologous PBMC photomodified with th e causative drug. Modest but significant proliferative responses of respond er lymphocytes were found in patients photosensitive to lomefloxacin, flero xacin, and enoxacin, indicating photoallergic mechanism in these patients. On the other hand, sparfloxacin-photosensitive patients exhibited negative lymphocyte stimulation test, suggesting that its photosensitivity is mainly phototoxic. When UVA-preirradiated quinolones were used as stimulators, on ly fleroxacin exceptionally stimulated patients' PBMC, indicating its proha ptenic as well as photohaptenic properties. These findings suggest the pres ence of circulating sensitized T cells in patients with photosensitivity to certain quinolones. (C) 1999 Elsevier Science Ireland Ltd. All rights rese rved.