High LDL and/or low HDL are risk factors for atherosclerosis and are also a common clinical feature in systemic lupus erythematosus, rheumatoid arthritis, and psoriasis. Here, we show that changes in lipid profiles that reflect atherosclerotic disease led to activation of skin murine dendritic cells (DCs) locally, promoted dermal inflammation, and induced lymph node hypertrophy. Paradoxically, DC migration to lymph nodes was impaired, suppressing immunologic priming. Impaired migration resulted from inhibitory signals generated by platelet-activating factor (PAF) or oxidized LDL that acts as a PAF mimetic. Normal DC migration and priming was restored by HDL or HDL-associated PAF acetylhydrolase (PAFAH), which mediates inactivation of PAF and oxidized LDL. Thus, atherosclerotic changes can sequester activated DCs in the periphery where they may aggravate local inflammation even as they poorly carry out functions that require their migration to lymph nodes. In this context, HDL and PAFAH maintain a normally functional DC compartment.
