The inventors discovered that the adhesion molecule CAR, known to be localized in intracellular adhesion sites, functioned as an adhesion molecule for activated lymphocytes. Further, the inventors identified CARL, a novel CAR ligand expressed in lymphocytes, and clarified that the ligand was expressed selectively in Th1 cells. In addition, they found that anti-CAR antibodies could inhibit the adhesion of activated lymphocytes to CAR molecules. Thus, the present invention provides methods for detecting Th1 cells using CAR or anti-CARL antibodies, and methods of screening for inhibitors suppressing the adhesion of Th1 cells using the binding between CAR and CARL as an index. Furthermore, the present invention relates to methods of screening for inhibitors of the binding between CAR and CARL, antibodies that inhibit the binding between CAR and CARL, and therapeutic compositions comprising these antibodies. These are expected to be useful in diagnosing diseases, such as inflammation, in which infiltration of Th1 cells is involved, and in providing pharmaceutical agents for alleviating such diseases.