An arrangement includes a voltage input, a reactive element connected in series with the voltage input, and an LED light source. This invention also provides a method for detecting or quantifying superantigens using MHC class II or a part thereof having an affinity to the superantigens, as well as an assay kit therefor. An iron is placed onto the optional non-stick sheet to drive the polyester and image into the receptor. The laser beam is separated into a 0-th order laser beam and \xb1 primary laser beams, which are made incident on the objective lens, pass therethrough, and are made incident on the recording surface of a disk.