Quantitative cell population data from Diffuse Cutaneous Leishmaniasis Lesions

Diffuse cutaneous leishmaniasis (DCL) is marked by persistent Leishmania amazonensis parasitism and a profoundly immunosuppressive tissue environment. Using multiparametric immunofluorescence, we investigate the immune landscape of DCL skin lesions. We observed large numbers of CD68⁺ phagocytes harbouring intracellular parasites that displayed prominent vacuolated morphology. Spatial mapping demonstrated distinct tissue compartments that were enriched for vacuolated (VA+) or non-vacuolated (VA-) phagocytes. Notably, CD4⁺FOXP3⁺ regulatory T cells were significantly enriched in VA+ regions, in close proximity to CD68⁺ cells, suggesting that macrophages containing parasites were associated with an immunosuppressive microenvironment. Consistent with this, immunofluorescence confirmed a preferential co-localisation of CD68⁺ cells expressing heme oxygenase-1 (HO-1), a key mediator of anti-inflammatory responses, within VA⁺ areas. Strikingly, a strong positive correlation was observed between HO-1⁺ phagocytes and Treg frequencies, supporting the hypothesis of a coordinated immunoregulatory axis contributing to immune evasion and parasite persistence. Collectively, our findings reveal a compartmentalised niches in DCL defined by the co-localisation of parasite engorged vacuolated macrophages and regulatory T cells that may underpin the immunosuppression observed in this severe form of this disease.