SUMMARY Effective innate immunity against many microbial pathogens requires macrophage programs that upregulate phagocytosis and direct antimicrobial pathways, two functions generally assumed to be coordinately regulated. Here the regulation of these key functions was investigated in human blood-derived macrophages. IL-10 induced the phagocytic pathway, including CD209 and scavenger receptors, resulting in phagocytosis of mycobacteria and oxLDL. IL-15 induced the vitamin D-dependent antimicrobial pathway and CD209, yet the cells were less phagocytic. The differential regulation of macrophage functional programs was confirmed by analysis of the spectrum of leprosy lesions: the macrophage phagocytosis pathway was prominent in the clinically progressive, multibacillary form, whereas the vitamin D-dependent antimicrobial pathway predominated in the self-limited form of the disease and in patients undergoing reversal reactions from the multibacillary to the self-limited form. These data indicate that macrophage programs for phagocytosis and antimicrobial responses are distinct and differentially regulated in innate immunity in bacterial infections.

Leprosy provides a model to investigate mechanisms of immune regulation in humans, given that the disease forms a clinical-immunological spectrum. Here, we identified 13 miRNAs that were differentially expressed in the lesions of subjects with progressive lepromatous (L-lep) vs. the self-limited tuberculoid (T-lep) disease. Bioinformatic analysis revealed a significant enrichment of L-lep-specific miRNAs that preferentially target key immune genes downregulated in L-lep vs. T-lep lesions. The most differentially expressed miRNA in L-lep lesions, hsa-mir-21, was upregulated in M. leprae-infected monocytes. Hsa-mir-21, by downregulating toll-like receptor 2/1 (TLR2/1)-induced CYP27B1 and IL1B as well as upregulating IL-10, inhibited gene expression of the vitamin D-dependent antimicrobial peptides, CAMP and DEFB4A. Conversely, knockdown of hsa-mir-21 in M. leprae-infected monocytes enhanced expression of CAMP and DEFB4A and restored TLR2/1-mediated antimicrobial activity against M. leprae. Therefore, the ability of M. leprae to upregulate hsa-mir-21 targets multiple genes associated with the immunologically localized disease form, providing an effective mechanism to escape from the vitamin D-dependent antimicrobial pathway.

Summary Macrophage (MΦ) polarization is triggered during the innate immune response to defend against microbial pathogens, but can also contribute to disease pathogenesis. In a previous study, we found that interleukin‐15 (IL‐15) ‐derived classically activated macrophages (M1 MΦ) have enhanced antimicrobial activity, whereas IL‐10‐derived alternatively activated macrophages (M2 MΦ) were highly phagocytic but lacked antimicrobial activity. Given that the ability to modulate MΦ polarization from M2 MΦ to M1 MΦ may promote a more effective immune response to infection, we investigated the plasticity of these MΦ programs. Addition of IL‐10 to M1 MΦ induced M2‐like MΦ, but IL‐15 had little effect on M2 MΦ. We determined the set of immune receptors that are present on M2 MΦ, elucidating two candidates for inducing plasticity of M2 MΦ, Toll‐like receptor 1 (TLR1) and interferonγ (IFN‐γ) receptor 1. Stimulation of M2 MΦ with TLR2/1 ligand (TLR2/1L) or IFN‐γ alone was not sufficient to alter M2 MΦ phenotype or function. However, co‐addition of TLR2/1L and IFN‐γ re‐educated M2 MΦ towards the M1 MΦ phenotype, with a decrease in the phagocytosis of lipids and mycobacteria, as well as recovery of the vitamin‐D‐dependent antimicrobial pathway compared with M2 MΦ maintained in polarizing conditions. Similarly, treatment of M2 MΦ with both TLR2/1L and anti‐IL‐10 neutralizing antibodies led to polarization to the M1‐like MΦ phenotype and function. Together, our data demonstrate an approach to induce MΦ plasticity that provides the potential for re‐educating MΦ function in human mycobacterial disease to promote host defense and limit pathogenesis.

The clinical data and blood samples of 48 Chinese children with FH and their parents were collected. Genomic DNA was isolated from peripheral blood leucocytes. The 48 children and their parents were examined for genetic variants in all coding exons and exon-intron boundaries of genes by exome sequencing. Variants detected in the COL4A5, COL4A4 and COL4A3 genes by exome sequencing were further verified by Sanger sequencing. Pathogenicity of the identified variants was verified by bioinformatic analyses. The etiological diagnosis of some children with FH were made according to their genotypes and their phenotypes. Results: Twenty-five mutations were identified in 29 Chinese children with FH by exome sequencing and Sanger sequencing. Among them, 20 mutations, such as COL4A5 539G>A, COL4A5 3985delC, COL4A5 566G>T, COL4A5 2822G>A, COL4A5 EXON 29-30 deletions, COL4A4 4421C>T, COL4A4 4915G>C, COL4A4 2752G>A, COL4A4 1030-2A>C, COL4A4 2447G>A, COL4A4 4481delT, COL4A4 4288G>A, COL4A4 1567C>T, COL4A3 1496G>A, COL4A3 3619G>A, COL4A3 3627G>A, COL4A3 4700T>G, COL4A3 898G>A, COL4A3 2096T>C and COL4A3 4769G>A, were novel, and 5 mutations, such as COL4A5 2858G>T, COL4A5 530G>A, COL4A4 4599T>G, COL4A4 3499G>A and COL4A3 4235G>T, have already been reported. Muatations in the COL4A5, COL4A4 and COL4A3 gene were found in 60.4% (29/48) of 48 children with FH. An etiological diagnosis could be made in 56.3% (27/ 48) of 48 children with FH. Eleven children with FH were diagnosed with X-linked AS, and 1 child with FH was diagnosed with autosomal recessive AS, and 15 cases were diagnosed with either autosomal dominant AS or TBMN. Conclusions: It is necessary for the Chinese children with FH to make an etiological diagnosis by examing genetic variants of the COL4A5, COL4A4 and COL4A3 genes.

Leprosy is a human disease in which the clinical manifestations correlate with the host immune response to the pathogen, Mycobacterium leprae. In tuberculoid (T-lep) patients the infection is localized and Th1 cytokines predominate in lesions; whereas, in lepromatous patients (L-lep) the infection is disseminated and Th2 cytokines predominate. Evidence also suggests a role for the vitamin D-dependent antimicrobial pathway in contributing to host defense in leprosy. By profiling miRNAs in leprosy lesions, we identified 13 miRNAs differentially expressed in L-lep vs. T lep lesions. Bioinformatic analysis revealed a significant enrichment of L-lep-specific miRNAs that preferentially target genes important in T-lep lesions, including twelve Th1 and antimicrobial pathway genes. The most differentially expressed miRNA in L-lep lesions, hsa-mir-21, was upregulated in M. leprae-infected monocytes and induced by the mycobacterial virulence factor phenolic glycolipid-I (PGL-I). Hsa-mir-21, by downregulating Toll-like receptor induced CYP27B1 and IL1B and upregulating IL-10, inhibited the vitamin D-dependent antimicrobial peptide gene expression. In contrast, knockdown of hsa-mir-21 in M. leprae-infected monocytes enhanced antimicrobial peptide gene expression. The ability of the pathogen to upregulate hsa-mir-21 which targets multiple genes associated with the immunologically localized disease form provides an effective mechanism to escape the vitamin D antimicrobial pathway.