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5-Lipoxygenase (5-LO) catalyzes the initial steps in the formation of leukotrienes (LTs), which are implicated in immune reactions. Recently, it was shown that FITC-triggered epidermal Langerhans cell (LC) emigration to draining lymph nodes (LNs) is impaired in LTC4 export pump (multidrug resistance-associated protein 1)-deficient mice. Here, we sought genetic evidence for a role of endogenous LTs in dendritic cell function through the study of 5-LO-deficient mice. Though DC numbers in skin, spleen, and peripheral LNs were similar in both 5-LO-deficient and wild-type (WT) mice, DC homing from skin to draining LNs induced by FITC was reduced by 75% in 5-LO-deficient mice. Moreover, in WT mice, all epidermal LCs, dermal langerin+ LCs, and subsets of dermal macrophages and langerin+ LCs in T-cell areas of skin-draining LNs markedly expressed 5-LO. However, the enzyme was noticeably absent in all DC subsets of the dermis, thymus, spleen, Peyer's patches, mesenteric LNs, and mucosal surfaces of lung and intestine. As all epidermal cells other than LCs lacked 5-LO and because differentiation and activation of DCs generated from 5-LO-deficient mice in vitro were normal, these data support a selective role of endogenous LTs in DC homing following skin sensitization.

Atherosclerosis is a transmural chronic inflammatory condition of small and large arteries that is associated with adaptive immune responses at all disease stages. However, impacts of adaptive immune reactions on clinically apparent atherosclerosis such as intima lesion (plaque) rupture, thrombosis, myocardial infarction, and aneurysm largely remain to be identified. It is increasingly recognized that leukocyte infiltrates in plaque, media, and adventitia are distinct but that their specific roles have not been defined. To map these infiltrates, we employed laser-capture microdissection (LCM) to isolate the three arterial wall laminae using apoE⁻/⁻ mouse aorta as a model. RNA from LCM-separated tissues was extracted and large-scale, whole-genome expression microarrays were prepared. We observed that the quality of the resulting gene expression maps was compromised by tissue RNA carried over from adjacent laminae during LCM. To account for these flaws, we established quality controls and algorithms to improve the predictive power of LCM-derived microarray data. Our approach creates robust transcriptome atlases of normal and atherosclerotic aorta. Assessing LCM transcriptomes for immunity-related mRNAs indicated markedly distinctive gene expression patterns in the three laminae of the atherosclerotic aorta. These mouse mRNA expression data banks can now be mined to address a wide range of questions in cardiovascular biology.

Atherosclerosis is a transmural chronic inflammatory condition of small and large arteries that is associated with adaptive immune responses at all disease stages. However, impacts of adaptive immune reactions on clinically apparent atherosclerosis such as intima lesion (plaque) rupture, thrombosis, myocardial infarction, and aneurysm largely remain to be identified. It is increasingly recognized that leukocyte infiltrates in plaque, media, and adventitia are distinct but that their specific roles have not been defined. To map these infiltrates, we employed laser-capture microdissection (LCM) to isolate the three arterial wall laminae using apoE⁻/⁻ mouse aorta as a model. RNA from LCM-separated tissues was extracted and large-scale, whole-genome expression microarrays were prepared. We observed that the quality of the resulting gene expression maps was compromised by tissue RNA carried over from adjacent laminae during LCM. To account for these flaws, we established quality controls and algorithms to improve the predictive power of LCM-derived microarray data. Our approach creates robust transcriptome atlases of normal and atherosclerotic aorta. Assessing LCM transcriptomes for immunity-related mRNAs indicated markedly distinctive gene expression patterns in the three laminae of the atherosclerotic aorta. These mouse mRNA expression data banks can now be mined to address a wide range of questions in cardiovascular biology.