TLR2 and atherosclerosis: 28 These receptors were functional as demonstrated by increased perforin expression in CD28null T cells following stimulation with the TLR4 and TLR2 agonist lipopolysaccharide.28 Of note, both exogenous (microbial) and endogenous (e.g. HSP60) TLR agonists have been described in atherosclerotic plaques, and TLR2/4-mediated signals have been implicated in atherosclerosis.29 Whether TLR agonists contribute to CD28null T-cell activation in situ in atherosclerotic lesions warrants further investigation.