Background Inflammatory reactions have an important part in atherosclerosis. Smooth muscle cells, endothelial cells, monocytes, and T lymphocytes are actively involved. The purpose of this study was to assess whether T lymphocytes are activated in patients with stable angina pectoris who are candidates for a percutaneous transluminal coronary angioplasty (PTCA) and the influence of PTCA on this process.Methods and Results Twenty-four patients participated in the study. All were 40- to 60-year-old men, and all but one underwent successful PTCA. Blood samples were taken 1 day before PTCA and 1 week, 1 month, and 2 months after. Two groups of patients were detected: group A, 11 patients who had high levels of soluble interleukin-2 receptor (sIL-2R) before PTCA that decreased toward normal during the follow-up period in most of them; and group B, 13 patients who did not have elevated sIL-2R levels before PTCA and in whom sIL-2R levels did not change after the procedure. Group C consisted of 15 healthy men whose sIL-2R levels were in the normal range (control subjects).Conclusions (1) T lymphocytes are activated in stable angina patients. (2) The level of sIL-2R can be a reliable laboratory marker for follow-up of patients after PTCA, especially those with high sIL-2R levels before the procedure. (Circulation. 1995;91:20-22.)