In vitro and in vivo effect of PD‐1/PD‐L1 blockade on microglia/macrophage activation and T cell subset balance in cryptococcal meningitis

Abstract This study aimed to investigate the PD‐1/ PD‐L1 signaling pathway and its effects the activation of microglia/macrophage and balancing T cell subsets in cryptococcal meningitis (CM). A total of 126 CM patients and 126 healthy individuals were recruited for the study. The CM patients were treated with amphotericin B (AmB). Seventy five C57BL/6 mice were grouped into the normal control, CM model, CM + AmB, sham, and CM + PD‐1 antibodies (Ab) groups. CD4 + and CD8 + T cells as well as microglia/macrophages were analyzed by means of flow cytometry. Ionized calcium‐binding adaptor molecule 1 (Ibal) expression was detected using western blotting and immunohistochemistry techniques. And the expression of Rab5 and Rab11 were detected using an immunofluorescence assay. Both PD‐1 and PD‐L1 mRNA and protein expression among the mice in the study were evaluated by qRT‐PCR and western blotting methods. Compared to the CM model group, the CM + AmB and CM + PD‐1 Ab groups exhibited increased levels of Th1 cytokines and chemokines expression, and reduced levels of Th2 cytokines expressions. Elevated cell purity and viability of CD4 + T cell were recorded as well as increases in microglia, however, there were reductions in the number of CD8 + T cells. Depleted expressions of Ibal, Rab5, and Rab11 as well as reduced mRNA expressions of PD‐1 and PD‐L1 in CD4 + , microglia, and macrophage cells. The findings suggested that suppression of the PD‐1/PD‐L1 signaling pathway restricts the proliferation of CM by down‐regulating the expressions of Th2 cells and suppressing microglia and macrophage activation.