Perivascular clusters of Th2 cells and M2 macrophages in allergic contact dermatitis to methylchloroisothiazolinone and methylisothiazolinone.

BACKGROUND: Methylisothiazolinone (MI) and Methylchloroisothiazolinone (MCI) are among the most common skin sensitizers, yet the immunological events that occur during MCI/MI allergic contact dermatitis (ACD) are still poorly understood. OBJECTIVES: To analyse dendrocytes, macrophage subtypes and T cells in skin during the elicitation phase of MCI/MI ACD. METHODS: Thirteen patients with positive patch test reactions to MCI/MI (ACD group) and 11 individuals with negative patch test results were selected. Skin biopsies were only performed at 48 hours of patch testing. Immunohistochemistry was conducted to assess T cells, dendrocytes (Factor XIIIa), M1 (p-Stat1, CD68) and M2 (c-Maf, CD163) macrophages. Transcriptional analyses were performed for cytokines and related factors, and further compared to atopic dermatitis samples (n=4). Immunofluorescence assays addressed T cells location, along with IL-4 or IL-13, within the skin. RESULTS: MCI/MI elicited dermal dendrocytes and macrophages, pronouncedly the M2 subtype. T cells, majorly CD4+ T cells, accumulated in the perivascular areas. Similarly, abundant IL-4 protein was detected in these areas. There was an upregulation of IL-4 and IL-13 mRNA expression, a mild increase in IFNG mRNA levels and a down-regulation of RORC in the ACD group. Immunofluorescence revealed dermal clusters of T cells co-localized with IL-4. CONCLUSIONS: M2 macrophages and Th2 cells participate in the immunopathogenesis of MCI/MI ACD. Dermal dendrocytes and M2 macrophages may assist the formation of CD4+ T cells perivascular clusters. These findings render a mechanistic insight into the MCI/MI reaction. Further analysis at different timepoints of patch testing is required to fully comprehend this ACD kinetics.

High density of M2-macrophages in acral lentiginous melanoma compared to superficial spreading melanoma.

AIMS: Acral lentiginous melanoma (ALM) is the most common type of melanoma in people with darker skin phototypes. There is some evidence that the aetiology, pathogenesis, risk factors and natural history of ALM differ from those of superficial spreading melanoma (SSM). ALM behaves more aggressively than SSM, but the biological explanation for these differences remains unknown. The presence of one subtype of macrophages, termed M2-macrophage (M2-M), has been found to be related to local progression, metastasis and poor prognosis in several neoplasms. The aim of this study was to compare the density of M2-Ms in ALMs versus SSMs, and to examine whether or not the density of M2-Ms is associated with histopathological features predictive of adverse prognosis in cutaneous melanoma (CM), as well as development of metastasis. METHODS AND RESULTS: Sixty-seven ALMs and 67 SSMs cases were analysed. The tumours were classified according to thickness, ulceration, mitosis and metastasis. M2-M quantity was evaluated using immunohistochemistry with anti-CD163 and anti-CD206 antibodies. M2-Ms were increased in ALM compared with SSM, and were related to the histopathological features predictive of adverse prognosis in CM, such as thickness > 1.0 mm, ulceration and mitotic activity, and the development of metastasis. CONCLUSIONS: Our study is the first, to our knowledge, to demonstrate the increased presence of M2-Ms in ALM compared with SSM. Our findings suggest that the increased M2-Ms in ALM are associated with the main histopathological features predictive of adverse prognosis in CM, as well as the presence of metastasis, and that these cells can be related to the aggressive behaviour seen in ALMs.

Analysis of serum levels and cutaneous expression of lipoprotein (a) in 38 patients with livedoid vasculopathy.

BACKGROUND: Coagulation disorders contribute to the development of livedoid vasculopathy (LV). Elevated plasma levels of lipoprotein(a) [Lp(a)] are an independent risk factor for the development of cardiovascular disease and associated with hypercoagulable states. Increased serum Lp(a) levels have been reported in patients with LV and may have an important role in the pathogenesis of LV. OBJECTIVES: To investigate Lp(a) expression in skin lesions and circulating serum Lp(a) levels in patients with LV. METHODS: Skin biopsy samples from 38 patients (27 women and 11 men) with active lesions diagnosed as LV and 9 samples of normal skin (5 women and 4 men) from control patients without LV were evaluated for skin expression of Lp(a) by immunohistochemistry. Plasma levels of Lp(a) were analyzed by immunoturbidimetry. RESULTS: We found that lesional skin in patients with LV expressed 10-fold higher Lp(a) immunostaining than controls. High plasma levels of Lp(a) were observed in LV patients. We did not find a correlation (P = .02) between expression of Lp(a) in the skin and plasma levels of Lp(a) in patients with LV. CONCLUSIONS: Increased Lp(a) expression in lesional skin of LV patients suggests the role of Lp(a) in the thrombo-occlusive vasculopathy observed in this disease.