Status of B-Lymphocyte Subsets and Their Homing Markers in Patients With Post-Kala-Azar Dermal Leishmaniasis.

In visceral leishmaniasis, the Type II helper T cell predominance results in B cell modulation and enhancement of anti-leishmanial IgG. However, information regarding its dermal sequel, post-kala-azar dermal leishmaniasis (PKDL), remains limited. Accordingly, this study aimed to elucidate the B cell-mediated antibody-dependent/independent immune profiles of PKDL patients. In the peripheral blood of PKDL patients, immunophenotyping of B cell subsets was performed by flow cytometry and by immunohistochemistry at lesional sites. The functionality of B cells was assessed in terms of skin IgG by immunofluorescence, while the circulating levels of B cell chemoattractants (CCL20, CXCL13, CCL17, CCL22, CCL19, CCL27, CXCL9, CXCL10 and CXCL11) were evaluated by a multiplex assay. In patients with PKDL as compared with healthy controls, there was a significant decrease in pan CD19⁺ B cells. However, within the CD19⁺ B cell population, there was a significantly raised proportion of switched memory B cells (CD19⁺IgD^-CD27⁺) and plasma cells (CD19⁺IgD^-CD38⁺CD27⁺). This was corroborated at lesional sites where a higher expression of CD20⁺ B cells and CD138⁺ plasma cells was evident; they were Ki67 negative and demonstrated a raised IgG. The circulating levels of B cell chemoattractants were raised and correlated positively with lesional CD20⁺ B cells. The increased levels of B cell homing markers possibly accounted for their enhanced presence at the lesional sites. There was a high proportion of plasma cells, which accounted for the increased presence of IgG that possibly facilitated parasite persistence and disease progression.