B cell immune response to Talaromyces marneffei infection in HIV-negative patients and rat models.

PURPOSE: Talaromyces marneffei (T. marneffei), a thermally dimorphic fungus, causes systemic mycosis, with pathogenesis involving intracellular survival and dysregulation of host immunity. This study investigates the phenotypic and functional alterations in B lymphocytes induced by T. marneffei infection. METHODS: Retrospective analysis of peripheral blood B cell counts and IgG/IgM levels in 31 HIV-negative Talaromycosis (TSM) patients. Peripheral blood samples were collected to measure plasmablasts, plasma cells and related cytokine expression. The plasmablasts and plasma cells in spleen was determined using flow cytometry in T. marneffei infected rat models, and the levels of IgG/IgM, B-cell activating factor (BAFF), A Proliferation-Inducing Ligand (APRIL) and IL-21 were determined. RESULTS: TSM patients exhibited reduced CD19⁺B cell and plasmablasts proportions in peripheral blood, while plasma cell proportions increased significantly and IgG, IgM levels in serum were elevated. In T. marneffei infected rats, the proportion of plasmablasts and plasma cells in splenic lymphocytes increased, and levels of IgG, IgM, BAFF, APRIL and IL-21 were significantly elevated compared to normal control rats. CONCLUSION: T. marneffei infection induces B-cell phenotypic and functional abnormalities, manifested as reduced B-cell numbers, increased proportions of plasma cells, accompanied by upregulation of BAFF, APRIL, and IL-21 expression. This suggests T. marneffei may participate in pathogenesis by regulating B-cell differentiation and humoral immune responses. CLINICAL TRIAL NUMBER: Not applicable.