 The purpose of this study is to determine what types of cells participate in the defense of humans against Leishmania skin parasites. People 18-70 years of age who have leishmaniasis, have healed leishmanial lesions, or are healthy are being invited to participate in this study. Approximately 150 people will participate in the study. Participants will be asked to provide some general information about themselves and about skin sores, if they have any. A skin test will be performed and a blood sample will be obtained. This study involves up to 3 visits; the first visit will last up to 5 hours and the second visit will last for 30 minutes. The third visit may be scheduled within 3 days after the second visit. 