T lymphocyte lines isolated from atheromatous plaque contain cells capableof responding to Chlamydia antigens

Chlamydia pneumoniae infection is associated with atherosclerosis and the o rganism has been identified in arterial lesions. To determine whether T lym phocyte-mediated immune responses to Chlamydia antigens within plaque could contribute to pathogenesis, we have derived T cell lines from atherosclero tic plaques of 32 patients. Culture with IL-2 alone proved insufficient for cellular activation and expansion, but additional stimulation with phytoha emagglutinin (PHA) or recall antigens allowed consistent establishment of T cell lines. Furthermore, in cultures of approx. 500 tissue fragments, Chla mydia organisms proved as effective as other recall antigens in producing o utgrowth of arterial T cells (20-25% wells produced T cell lines). Testing the antigen responsiveness of T cell lines showed that those derived using Chlamydia organisms were more likely to respond to Chlamydia (5/29+) than t hose isolated using other stimuli (6/69+ for PHA; 5/57+ for PPD and tetanus toxoid (TT)). However, lines responsive to each of the recall antigens wer e observed. Using recombinant Chlamydia antigens, some Chlamydia-specific T cell lines were shown to respond to OMP2 and/or hsp60. Those recognizing C hlamydia hsp60 did not cross-react with human hsp60, but human hsp60-respon sive lines were also observed. Thus, atherosclerotic plaque tissue contains a variety of memory T lymphocytes, and amongst these are cells capable of recognizing Chlamydia antigens. In a C. pneumoniae-infected plaque, such T cells may be activated by local antigen and could contribute to the inflamm atory process in the arterial wall through CD40 ligand expression and cytok ine secretion.