Chlamydia pneumoniae reactive T lymphocytes in the walls of abdominal aortic aneurysms

Background The presence of Chlamydia pneumoniae in the walls of abdominal a ortic aneurysms (AAAs) has been demonstrated recently, but its role in the cause and/or maintenance of aortic wall inflammation is not known. In the p resent study, we have investigated the possible relationship between C. pne umoniae and the antigen specificity of T lymphocytes mediating inflammation in AAA tissue. Materials and methods Tissue specimens were obtained from 22 consecutive AA A patients undergoing elective surgery (mean age 67 +/- 1 year). Immunohist ochemical analysis of the formalin-fixed tissue was performed using the str eptavidin-biotin-peroxidase method. In vivo activated T lymphocytes were pr opagated from the specimens with interleukin (IL) 2, and antigen specificit y of the established T-cell lines was analysed in the presence of autologou s antigen-presenting cells using radioactive thymidine labelling. Results Immunohistological staining of AAA tissue showed the presence of C. pneumoniae antigen in 55% (6/11) of the samples studied. The inflammatory cell infiltrate of the AAA tissue contained 60-90% T (CD45RO) and 0-10% B ( CD20) cells. When the tissue specimens were cultured without antigen in the presence of IL-2, lymphocyte propagation was achieved in 17 out of the 22 samples. Chlamydia pneumoniae antigen was found to induce a positive prolif erative response in 8 of the 17 lines. Conclusions The presence of C. pneumoniae specific T lymphocytes among in v ivo activated cells from the AAA tissue specimens suggests that C. pneumoni ae participates in the maintenance of the inflammatory response in the tiss ue and may thus be involved in the progression of the disease.