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

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.