Background CD40 ligand (CD40L) deficiency predisposes to opportunistic infections including those caused by fungi and intracellular bacteria. Studies of CD40L-deficient patients reveal the critical role of CD40L-CD40 interaction for the function of T, B, and dendritic cells. However, the consequences of CD40L deficiency on macrophage function remain poorly understood.
Objectives To analzye the role of CD40L-CD40 interaction in macrophages immune response.
Methods MDMs were challenged with Paracoccidioides brasiliensis (Pb18, a highly virulent isolate) and the microbicidal activity determined by counting colony forming units (CFU). MDMs oxidative burst was measured by luminol-dependent chemiluminescence (LDCL). Supernatants of macrophages treated or untreated with rhIFN-γ or sCD40L were harvested 48 hours after P. brasiliensis or M. tuberculosis incubation and the Cytokine levels were evaluated by luminex. The analysis of M. tuberculosis (H37Rv strain) phagocytosis and proliferation control by MDMs were carried out by CFU counting. Macrophage transcriptome profiles from three CD40L deficient patients and three healthy controls were analyzed by RNAseq. All the experiments were performed before and after IFN-gamma in vitro treatment.
Results Here we show that macrophages from CD40L-deficient patients exhibit defective fungicidal activity and reduced oxidative burst, which improved in the presence of IFN-γ but not soluble CD40L (sCD40L). In contrast, both IFN-γ and sCD40L ameliorate impaired production of multiple inflammatory cytokines. Comparing the gene expression signature of macrophages from CD40L-deficient patients to that of controls, we identified 109 differentially expressed genes (DEGs). In vitro treatment of macrophages with IFN-γ decreased the number of DEGs to only 11, and similarly affected the expression of 528 non-DEGs (140 genes down-regulated and 388 up-regulated) comparing patients and healthy controls. Finally, the addition of IFN-γ reversed defective control of M. tuberculosis proliferation by patient macrophages.
Conclusions Our findings demonstrate that absence of CD40L impairs macrophage development and function. In addition, the improvement of macrophage immune responses by IFN-γ suggests this cytokine as a potential new therapeutic option for patients with CD40L deficiency.
Disclosure of Interest None declared