Adaptive immune response to the autoantigen LL-37 differentiates atherosclerotic cardiovascular disease phenotypes

Atherosclerosis is the common underlying pathology in atherosclerotic cardiovascular disease (ASCVD) phenotypes of myocardial infarction (MI), stroke or peripheral artery disease (PAD). Single immune cell profiling of atherosclerotic plaques demonstrates a site-specific immune profile associated with the ASCVD phenotype, and LL-37 is a reported autoantigen in atherosclerosis.

To investigate whether the immune response to LL-37 would be common among different ASCVD phenotypes.

Peripheral blood mononuclear cells (PBMCs) and plasma were collected from stable ASCVD patients enrolled within 12 months after MI or stroke or diagnosed with PAD. A subgroup of post-acute patients provided PBMCs at follow-up (14.7 ± 3.6 months). T-cell response to LL-37 was profiled using activation-induced markers. LL-37 IgG, immune complex (IC) levels and subclass were evaluated with ELISA. LDL is a reported binding partner of LL-37 in plasma. Therefore, cross-reactivity of LL-37 IgG-ICs with native LL-37 or LL-37 complexed with LDL (LL-37_LDL) was assessed using immune depletion.

LL-37 provokes increased CD4⁺CD25⁺CD134⁺ T-cell response in stable post-MI patients whereas CD8⁺CD25⁺CD69⁺ T cells were reduced in PAD. CD4⁺ T-cell response to LL-37 in post-MI patients persisted at follow-up with increased CD4⁺CD25⁺CD69⁺FoxP3⁺ T regulatory cells while post-stroke patients had increased CD8⁺CD134⁺ T cells. LL-37 IgG-ICs were significantly increased in ASCVD patients with IgG3 subclass reduced in post-MI compared to post-stroke. Immune-depletion showed cross-reactivity of LL-37 IgG-ICs with both native LDL and LL-37_LDL only in post-MI plasma.

LL-37 antigen specific profiling of immune response may differentiate various ASCVD phenotypes and provide mechanistic insight in pathophysiology.