Immune responses to Chlamydia antigens in atherosclerosis

Aim of this study was to isolate T lymphocytes from atheromatous plaques and to determine they respond to Chlamydia antigens. Atheromatous plaques from carotid endarterectomy patients, were cultured in vitro with the T cell growth factor, IL-2. This rarely allowed outgrowth of T cell lines. However, when combined with a mitogenic or antigenic stimulus to T cells, T cell lines were obtained from most patients, and from similar to 30% of replicate plague tissue fragments. Chlamydia organisms were as effective in allowing the establishment of T cell lines as other recall antigens. T cell lines were tested for their ability to recognize antigens presented by autologous macrophages. Some lines responded to Chlamydia organisms, and also to the recombinant Chlamydia proteins hsp60 and OMP2. However, other lines recognized recall antigens. These results indicate that the atheromatous plague contains memory T lymphocytes, and amongst the antigens they recognize are Chlamydia proteins. Stimulation of T cells was required to allow outgrowth in vitro, suggesting that the T cells were not in an activated state in vivo. However, since Chlamydia pneumoniae is present in the atheromatous prague, activation of Chlamydia-reactive T cells by local antigen is a potential pro-inflammatory mechanism which could contribute to the pathogenesis of atherosclerosis.