Immune mapping of human tuberculosis and sarcoidosis lung granulomas.

Tuberculosis (TB) and sarcoidosis are both granulomatous diseases. Here, we compared the immunological microenvironments of granulomas from TB and sarcoidosis patients using in situ sequencing (ISS) transcriptomic analysis and multiplexed immunolabeling of tissue sections. TB lesions consisted of large necrotic and cellular granulomas, whereas "multifocal" granulomas with macrophages or epitheloid cell core and a T-cell rim were observed in sarcoidosis samples. The necrotic core in TB lesions was surrounded by macrophages and encircled by a dense T-cell layer. Within the T-cell layer, compact B-cell aggregates were observed in most TB samples. These B-cell clusters were vascularized and could contain defined B-/T-cell and macrophage-rich areas. The ISS of 40-60 immune transcripts revealed the enriched expression of transcripts involved in homing or migration to lymph nodes, which formed networks at single-cell distances in lymphoid areas of the TB lesions. Instead, myeloid-annotated regions were enriched in CD68, CD14, ITGAM, ITGAX, and CD4 mRNA. CXCL8 and IL1B mRNA were observed in granulocytic areas in which M. tuberculosis was also detected. In line with ISS data indicating tertiary lymphoid structures, immune labeling of TB sections expressed markers of high endothelial venules, follicular dendritic cells, follicular helper T cells, and lymph-node homing receptors on T cells. Neither ISS nor immunolabeling showed evidence of tertiary lymphoid aggregates in sarcoidosis samples. Together, our finding suggests that despite their heterogeneity, the formation of tertiary immune structures is a common feature in granulomas from TB patients.

HIF-1 stabilization in T cells hampers the control of Mycobacterium tuberculosis infection.

The hypoxia-inducible factors (HIFs) regulate the main transcriptional pathway of response to hypoxia in T cells and are negatively regulated by von Hippel-Lindau factor (VHL). But the role of HIFs in the regulation of CD4 T cell responses during infection with M. tuberculosis isn't well understood. Here we show that mice lacking VHL in T cells (Vhl cKO) are highly susceptible to infection with M. tuberculosis, which is associated with a low accumulation of mycobacteria-specific T cells in the lungs that display reduced proliferation, altered differentiation and enhanced expression of inhibitory receptors. In contrast, HIF-1 deficiency in T cells is redundant for M. tuberculosis control. Vhl cKO mice also show reduced responses to vaccination. Further, VHL promotes proper MYC-activation, cell-growth responses, DNA synthesis, proliferation and survival of CD4 T cells after TCR activation. The VHL-deficient T cell responses are rescued by the loss of HIF-1α, indicating that the increased susceptibility to M. tuberculosis infection and the impaired responses of Vhl-deficient T cells are HIF-1-dependent.

High Glucose and Carbonyl Stress Impair HIF-1-Regulated Responses and the Control of Mycobacterium tuberculosis in Macrophages.

Diabetes mellitus (DM) increases the risk of developing tuberculosis (TB), but the mechanisms behind diabetes-TB comorbidity are still undefined. Here, we studied the role of hypoxia-inducible factor-1 (HIF-1), a main regulator of metabolic and inflammatory responses, in the outcome of Mycobacterium tuberculosis infection of bone marrow-derived macrophages (BMM). We observed that M. tuberculosis infection of BMM increased the expression of HIF-1α and HIF-1-regulated genes. Treatment with the hypoxia mimetic deferoxamine (DFO) further increased levels of HIF-1-regulated immune and metabolic molecules and diminished the intracellular bacterial load in BMM and in the lungs of infected mice. The expression of HIF-1-regulated immunometabolic genes was reduced, and the intracellular M. tuberculosis levels were increased in BMM incubated with high-glucose levels or with methylglyoxal (MGO), a reactive carbonyl compound elevated in DM. In line with the in vitro findings, high M. tuberculosis levels and low HIF-1-regulated transcript levels were found in the lungs from hyperglycemic Leprdb/db compared with wild-type mice. The increased intracellular M. tuberculosis growth and the reduced expression of HIF-1-regulated metabolic and inflammatory genes in BMM incubated with MGO or high glucose were reverted by additional treatment with DFO. Hif1a-deficient BMM showed ablated responses of immunometabolic transcripts after mycobacterial infection at normal or high-glucose levels. We propose that HIF-1 may be targeted for the control of M. tuberculosis during DM. IMPORTANCE People living with diabetes who are also infected with M. tuberculosis are more likely to develop tuberculosis disease (TB). Why diabetic patients have an increased risk for developing TB is not well understood. Macrophages, the cell niche for M. tuberculosis, can express microbicidal mechanisms or be permissive to mycobacterial persistence and growth. Here, we showed that high glucose and carbonyl stress, which mediate diabetes pathogenesis, impair the control of intracellular M. tuberculosis in macrophages. Infection with M. tuberculosis stimulated the expression of genes regulated by the transcription factor HIF-1, a major controller of the responses to hypoxia, resulting in macrophage activation. High glucose and carbonyl compounds inhibited HIF-1 responses by macrophages. Mycobacterial control in the presence of glucose or carbonyl stress was restored by DFO, a compound that stabilizes HIF-1. We propose that HIF-1 can be targeted to reduce the risk of developing TB in people with diabetes.

Spatial Resolution of Mycobacterium tuberculosis Bacteria and Their Surrounding Immune Environments Based on Selected Key Transcripts in Mouse Lungs.

Mycobacterium tuberculosis (Mtb) bacilli are the causative agent of tuberculosis (TB), a major killer of mankind. Although it is widely accepted that local interactions between Mtb and the immune system in the tuberculous granuloma determine whether the outcome of infection is controlled or disseminated, these have been poorly studied due to methodological constraints. We have recently used a spatial transcriptomic technique, in situ sequencing (ISS), to define the spatial distribution of immune transcripts in TB mouse lungs. To further contribute to the understanding of the immune microenvironments of Mtb and their local diversity, we here present two complementary automated bacteria-guided analysis pipelines. These position 33 ISS-identified immune transcripts in relation to single bacteria and bacteria clusters. The analysis was applied on new ISS data from lung sections of Mtb-infected C57BL/6 and C3HeB/FeJ mice. In lungs from C57BL/6 mice early and late post infection, transcripts that define inflammatory macrophages were enriched at subcellular distances to bacteria, indicating the activation of infected macrophages. In contrast, expression patterns associated to antigen presentation were enriched in non-infected cells at 12 weeks post infection. T-cell transcripts were evenly distributed in the tissue. In Mtb-infected C3HeB/FeJ mice, transcripts characterizing activated macrophages localized in apposition to small bacteria clusters, but not in organized granulomas. Despite differences in the susceptibility to Mtb, the transcript patterns found around small bacteria clusters of C3HeB/FeJ and C57BL/6 mice were similar. Altogether, the presented tools allow us to characterize in depth the immune cell populations and their activation that interact with Mtb in the infected lung.

TRIM21 controls Toll-like receptor 2 responses in bone-marrow-derived macrophages.

TRIM21 is an interferon-stimulated E3 ligase that controls the activity of pattern-recognition signaling via ubiquitination of interferon regulatory factors and DDX41. Previous studies on the role of TRIM21 in innate immune responses have yielded contradictory results, suggesting that the role of TRIM21 is cell specific. Here, we report that bone-marrow-derived macrophages (BMDMs) generated from Trim21-/- mice have reduced expression of mature macrophage markers. Reflecting their reduced differentiation in response to macrophage colony-stimulating factor (M-CSF), Trim21-/- BMDMs had decreased expression of M-CSF signature genes. Although Trim21-/- BMDMs responded normally to Toll-like receptor 9 (TLR9) activation, they produced lower levels of pro-inflammatory cytokines in response to the TLR2 agonist PAM3CSK4. In line with this, the response to infection with the Bacillus Calmette-Guérin strain of Mycobacterium bovis was also diminished in Trim21-/- BMDMs. Our results indicate that TRIM21 controls responses to TLR2 agonists.

Spatial and temporal localization of immune transcripts defines hallmarks and diversity in the tuberculosis granuloma.

Granulomas are the pathological hallmark of tuberculosis (TB) and the niche where bacilli can grow and disseminate or the immunological microenvironment in which host cells interact to prevent bacterial dissemination. Here we show 34 immune transcripts align to the morphology of lung sections from Mycobacterium tuberculosis-infected mice at cellular resolution. Colocalizing transcript networks at <10 µm in C57BL/6 mouse granulomas increase complexity with time after infection. B-cell clusters develop late after infection. Transcripts from activated macrophages are enriched at subcellular distances from M. tuberculosis. Encapsulated C3HeB/FeJ granulomas show necrotic centers with transcripts associated with immunosuppression (Foxp3, Il10), whereas those in the granuloma rims associate with activated T cells and macrophages. We see highly diverse networks with common interactors in similar lesions. Different immune landscapes of M. tuberculosis granulomas depending on the time after infection, the histopathological features of the lesion, and the proximity to bacteria are here defined.

Synergistic antibacterial activity of silver with antibiotics correlating with the upregulation of the ROS production.

Thiol-dependent enzymes, including the thioredoxin (Trx) and glutathione (GSH) systems, have recently been found as promising bactericidal targets in multidrug-resistant (MDR) bacteria. We previously discovered that silver acted synergistically with ebselen in the inhibition of the Trx system and also resulted in a fast depletion of GSH in Gram-negative bacteria. Silver has been found by others to improve the sensitivity of bacteria to certain conventional antibiotics. Here, we found that the synergistic antibacterial effects of silver with four conventional antibiotics was correlated with the blockage of bacterial Trx system by silver. The synergistic antibacterial effect came along with the production of reactive oxygen species. All these results suggested that silver primarily enhanced the bactericidal activities of conventional antibiotics towards Gram-negative strains through the upregulation of ROS production.

STAT3 expression by myeloid cells is detrimental for the T- cell-mediated control of infection with Mycobacterium tuberculosis.

STAT3 is a master regulator of the immune responses. Here we show that M. tuberculosis-infected stat3fl/fl lysm cre mice, defective for STAT3 in myeloid cells, contained lower bacterial load in lungs and spleens, reduced granuloma extension but higher levels of pulmonary neutrophils. STAT3-deficient macrophages showed no improved control of intracellular mycobacterial growth. Instead, protection associated to elevated ability of stat3fl/fl lysm cre antigen-presenting cells (APCs) to release IL-6 and IL-23 and to stimulate IL-17 secretion by mycobacteria-specific T cells. The increased IL-17 secretion accounted for the improved control of infection since neutralization of IL-17 receptor A in stat3fl/fl lysm cre mice hampered bacterial control. APCs lacking SOCS3, which inhibits STAT3 activation via several cytokine receptors, were poor inducers of priming and of the IL-17 production by mycobacteria-specific T cells. In agreement, socs3fl/fl cd11c cre mice deficient of SOCS3 in DCs showed increased susceptibility to M. tuberculosis infection. While STAT3 in APCs hampered IL-17 responses, STAT3 in mycobacteria-specific T cells was critical for IL-17 secretion, while SOCS3 in T cells impeded IL-17 secretion. Altogether, STAT3 signalling in myeloid cells is deleterious in the control of infection with M. tuberculosis.

CISH controls bacterial burden early after infection with Mycobacterium tuberculosis in mice.

CISH gene has been associated with increased susceptibility to human tuberculosis. We found that cish-/- mice had higher M. tuberculosis load in spleens and lungs up to 2.5 weeks after infection but not later compared to controls. Cish mRNA levels were increased in lungs at early and late time points after M. tuberculosis infection. In relation, the titers of inos and tnf mRNA in lungs were reduced early after infection of cish-/- mice. The transfer of cish-/- and control T cells conferred rag1-/- mice similar protection to infection with M. tuberculosis. Macrophages showed increased cish mRNA levels after M. tuberculosis infection in vitro. However, mycobacterial uptake and growth in cish-/- and control macrophages was similar. Thus, we here show that CISH mediates control of M. tuberculosis in mice early after infection via regulation of innate immune mechanisms.

Id3 Maintains Foxp3 Expression in Regulatory T Cells by Controlling a Transcriptional Network of E47, Spi-B, and SOCS3.

The transcription factor Foxp3 dominantly controls regulatory T (Treg) cell function, and only its continuous expression guarantees the maintenance of full Treg cell-suppressive capacity. However, transcriptional regulators maintaining Foxp3 transcription are incompletely described. Here, we report that high E47 transcription factor activity in Treg cells resulted in unstable Foxp3 expression. Under homeostatic conditions, Treg cells expressed high levels of the E47 antagonist Id3, thus restricting E47 activity and maintaining Foxp3 expression. In contrast, stimulation of Id3-deficient or E47-overexpressing Treg cells resulted in the loss of Foxp3 expression in a subset of Treg cells in vivo and in vitro. Mechanistic analysis indicated that E47 activated expression of the transcription factor Spi-B and the suppressor of cytokine signaling 3 (SOCS3), which both downregulated Foxp3 expression. These findings demonstrate that the balance of Id3 and E47 controls the maintenance of Foxp3 expression in Treg cells and, thus, contributes to Treg cell plasticity.

Nitric Oxide Protects against Infection-Induced Neuroinflammation by Preserving the Stability of the Blood-Brain Barrier.

Nitric oxide (NO) generated by inducible NO synthase (iNOS) is critical for defense against intracellular pathogens but may mediate inflammatory tissue damage. To elucidate the role of iNOS in neuroinflammation, infections with encephalitogenic Trypanosoma brucei parasites were compared in inos(-/-) and wild-type mice. Inos(-/-) mice showed enhanced brain invasion by parasites and T cells, and elevated protein permeability of cerebral vessels, but similar parasitemia levels. Trypanosome infection stimulated T cell- and TNF-mediated iNOS expression in perivascular macrophages. NO nitrosylated and inactivated pro-inflammatory molecules such as NF-κΒp65, and reduced TNF expression and signalling. iNOS-derived NO hampered both TNF- and T cell-mediated parasite brain invasion. In inos(-/-) mice, TNF stimulated MMP, including MMP9 activity that increased cerebral vessel permeability. Thus, iNOS-generated NO by perivascular macrophages, strategically located at sites of leukocyte brain penetration, can serve as a negative feed-back regulator that prevents unlimited influx of inflammatory cells by restoring the integrity of the blood-brain barrier.

Suppressor of cytokine signaling-1 and chemokine (C-X-C Motif) receptor 3 expressions are associated with caseous necrosis in granulomas from patients with tuberculous lymphadenitis.

We investigated the role of suppressor of cytokine signaling-1 (SOCS1) and SOCS3 molecules in lymph nodes from tuberculous lymphadenitis patients (LNTB). Fewer T cells were noted in LNTB cases, which also had raised chemokine (C-X-C motif) receptor 3 (CXCR3) levels. In addition, we observed a positive correlation between CXCR3 and SOCS1 expression. Our data suggest that upregulation of SOCS1 molecules may contribute to the dissemination of Mycobacterium tuberculosis from granulomas.

Microinjection of Francisella tularensis and Listeria monocytogenes reveals the importance of bacterial and host factors for successful replication.

Certain intracellular bacteria use the host cell cytosol as the replicative niche. Although it has been hypothesized that the successful exploitation of this compartment requires a unique metabolic adaptation, supportive evidence is lacking. For Francisella tularensis, many genes of the Francisella pathogenicity island (FPI) are essential for intracellular growth, and therefore, FPI mutants are useful tools for understanding the prerequisites of intracytosolic replication. We compared the growth of bacteria taken up by phagocytic or nonphagocytic cells with that of bacteria microinjected directly into the host cytosol, using the live vaccine strain (LVS) of F. tularensis; five selected FPI mutants thereof, i.e., ΔiglA, ΔiglÇ ΔiglG, ΔiglI, and ΔpdpE strains; and Listeria monocytogenes. After uptake in bone marrow-derived macrophages (BMDM), ASC(-/-) BMDM, MyD88(-/-) BMDM, J774 cells, or HeLa cells, LVS, ΔpdpE and ΔiglG mutants, and L. monocytogenes replicated efficiently in all five cell types, whereas the ΔiglA and ΔiglC mutants showed no replication. After microinjection, all 7 strains showed effective replication in J774 macrophages, ASC(-/-) BMDM, and HeLa cells. In contrast to the rapid replication in other cell types, L. monocytogenes showed no replication in MyD88(-/-) BMDM and LVS showed no replication in either BMDM or MyD88(-/-) BMDM after microinjection. Our data suggest that the mechanisms of bacterial uptake as well as the permissiveness of the cytosolic compartment per se are important factors for the intracytosolic replication. Notably, none of the investigated FPI proteins was found to be essential for intracytosolic replication after microinjection.

SOCS3 and STAT3, major controllers of the outcome of infection with Mycobacterium tuberculosis.

In our review, we address the role of signal transducer and activator of transcription-3 (STAT3) and suppressor of cytokine signaling-3 (SOCS3) in the outcome of Mycobacterium tuberculosis infection, focusing on functions of these molecules in regulating the biology of myeloid and lymphoid cells. The STAT3 transcription factor has paradoxical roles: mainly activating an anti-inflammatory program in myeloid cells while promoting the differentiation and activation of inflammatory T cells. STAT3 is a major player in all phases of T cell responses, including T cell subset differentiation, T cell activation, and generation of memory. We review the roles of cytokines that activate, or are activated by, STAT3 during the infection with M. tuberculosis. SOCS3 inhibits STAT3 activation, by some but not all STAT3-activating cytokine receptors. Infection with M. tuberculosis also stimulates SOCS3 expression in phagocytes. Studies in different mouse models have proven the critical importance of SOCS3 in restraining inflammation and allowing optimal levels of protective immune responses against the infection. The accumulated data presented here suggest a relevant program coordinated by SOCS3 in different cell populations, which results in improved control of infection with M. tuberculosis. STAT3 and SOCS3 may thus be targeted to improve the control of infection with M. tuberculosis or the efficiency of vaccination.

SOCS3, a Major Regulator of Infection and Inflammation.

In this review, we describe the role of suppressor of cytokine signaling-3 (SOCS3) in modulating the outcome of infections and autoimmune diseases as well as the underlying mechanisms. SOCS3 regulates cytokine or hormone signaling usually preventing, but in some cases aggravating, a variety of diseases. A main role of SOCS3 results from its binding to both the JAK kinase and the cytokine receptor, which results in the inhibition of STAT3 activation. Available data also indicate that SOCS3 can regulate signaling via other STATs than STAT3 and also controls cellular pathways unrelated to STAT activation. SOCS3 might either act directly by hampering JAK activation or by mediating the ubiquitination and subsequent proteasome degradation of the cytokine/growth factor/hormone receptor. Inflammation and infection stimulate SOCS3 expression in different myeloid and lymphoid cell populations as well as in diverse non-hematopoietic cells. The accumulated data suggest a relevant program coordinated by SOCS3 in different cell populations, devoted to the control of immune homeostasis in physiological and pathological conditions such as infection and autoimmunity.

T cells modulate Epstein-Barr virus latency phenotypes during infection of humanized mice.

UNLABELLED: Human B cells, the main target of Epstein-Barr virus (EBV), can display several types of latent viral protein expression, denoted 0, I, IIa, IIb, or III. Of these, only type III expression induces proliferation of cells in vitro. These latency types are present at specific stages of infection and are also characteristic of different tumor types, but their generation is not fully understood. In this study, we analyzed the role of T cells in the regulation of EBV viral latency by using humanized NOD/SCID/IL2Rγ(-/-) mice. Several spleens presented macroscopic tumors 4 weeks after infection. Explanted spleen B cells from some of the EBV-infected mice proliferated in vitro, but this was usually lowered when cyclosporine was added to the cultures. This suggested that the in vitro growth of EBV-infected B cells required T cell help; thus, cells other than type III cells were also present in the spleens. Quantitative PCR analysis of promoter activities specific for the different EBV latency types confirmed that in addition to type III cells, type IIa and type I cells were present in the spleen. The relative usage of the viral promoter specific for I and IIa latency types (Q promoter) was higher in CD8(+) cell-depleted mice, and it was absent from CD4(+) cell-depleted mice. These results indicate that CD4(+) T cells are necessary for the generation/maintenance of cells with latency I/IIa in the humanized mice. CD4(+) T cells contributed to this process through their CD40L expression. IMPORTANCE: At primary infection with EBV, the infected B cells are proliferating and express viral proteins that have transforming potential. However, when the acute infection is resolved, in healthy individuals EBV is carried by a small fraction of B cells that express a restricted number of viral proteins unable to induce proliferation. Understanding the details of this transition is of fundamental importance. We studied this question in humanized mice by manipulating their different T cell compartments before and during infection with EBV. Our results indicate that CD4(+) T cells are responsible for the switch to a nonproliferating EBV program during primary infection with EBV.

Role of the Listeria monocytogenes 2-Cys peroxiredoxin homologue in protection against oxidative and nitrosative stress and in virulence.

Peroxiredoxins contribute to protection of some bacteria against reactive oxygen intermediates (ROIs) and reactive nitrogen intermediates (RNIs). Listeria monocytogenes, a facultative intracellular bacterial pathogen, interacts with ROIs and RNIs during infection. In this study, we investigated the involvement of the 2-Cys peroxiredoxin (Prx) homologue in L. monocytogenes in the protection against ROIs and RNIs and in virulence through the construction of an in-frame prx deletion mutant. The Δprx mutant had increased sensitivity to hydrogen peroxide and cumene hydroperoxide compared to the wild-type strain. The mutant also exhibited an increased susceptibility to the nitric oxide-generating compound S-nitroso-N-acetylpenicillamine (SNAP) and 3-morpholinosydnonimine hydrochloride (SIN-1), a peroxynitrite donor. Furthermore, a diminished virulence of the Δprx mutant relative to the wild-type was observed in C57BL/6 mice, but not in inducible nitric oxide synthase-deficient mice. The results suggest that Prx protects L. monocytogenes against oxidative and nitrosative stress in vitro and in vivo and that the prx-encoded polypeptide thereby is involved in L. monocytogenes virulence.

Structure-activity relationships of synthetic cordycepin analogues as experimental therapeutics for African trypanosomiasis.

Novel methods for treatment of African trypanosomiasis, caused by infection with Trypanosoma brucei are needed. Cordycepin (3'-deoxyadenosine, 1a) is a powerful trypanocidal compound in vitro but is ineffective in vivo because of rapid metabolic degradation by adenosine deaminase (ADA). We elucidated the structural moieties of cordycepin required for trypanocidal activity and designed analogues that retained trypanotoxicity while gaining resistance to ADA-mediated metabolism. 2-Fluorocordycepin (2-fluoro-3'-deoxyadenosine, 1b) was identified as a selective, potent, and ADA-resistant trypanocidal compound that cured T. brucei infection in mice. Compound 1b is transported through the high affinity TbAT1/P2 adenosine transporter and is a substrate of T. b. brucei adenosine kinase. 1b has good preclinical properties suitable for an oral drug, albeit a relatively short plasma half-life. We present a rapid and efficient synthesis of 2-halogenated cordycepins, also useful synthons for the development of additional novel C2-substituted 3'-deoxyadenosine analogues to be evaluated in development of experimental therapeutics.

Critical and independent role for SOCS3 in either myeloid or T cells in resistance to Mycobacterium tuberculosis.

Suppressor of cytokine signalling 3 (SOCS3) negatively regulates STAT3 activation in response to several cytokines such as those in the gp130-containing IL-6 receptor family. Thus, SOCS3 may play a major role in immune responses to pathogens. In the present study, the role of SOCS3 in M. tuberculosis infection was examined. All Socs3(fl/fl) LysM cre, Socs3(fl/fl) lck cre (with SOCS3-deficient myeloid and lymphoid cells, respectively) and gp130(F/F) mice, with a mutation in gp130 that impedes binding to SOCS3, showed increased susceptibility to infection with M. tuberculosis. SOCS3 binding to gp130 in myeloid cells conveyed resistance to M. tuberculosis infection via the regulation of IL-6/STAT3 signalling. SOCS3 was redundant for mycobacterial control by macrophages in vitro. Instead, SOCS3 expression in infected macrophages and DCs prevented the IL-6-mediated inhibition of TNF and IL-12 secretion and contributed to a timely CD4+ cell-dependent IFN-γ expression in vivo. In T cells, SOCS3 expression was essential for a gp130-independent control of infection with M. tuberculosis, but was neither required for the control of infection with attenuated M. bovis BCG nor for M. tuberculosis in BCG-vaccinated mice. Socs3(fl/fl) lck cre mice showed an increased frequency of γδ+ T cells in different organs and an enhanced secretion of IL-17 by γδ+ T cells in response to infection. Socs3(fl/fl) lck cre γδ+ T cells impaired the control of infection with M. tuberculosis. Thus, SOCS3 expression in either lymphoid or myeloid cells is essential for resistance against M. tuberculosis via discrete mechanisms.

CD4+ cell-dependent granuloma formation in humanized mice infected with mycobacteria.

We have used humanized mice, in which human immune cells differentiate de novo from transplanted cord blood progenitor cells, to study the human immune responses to infection with Mycobacterium bovis bacillus Calmette-Guérin and Mycobacterium tuberculosis. Granulomas with a core containing giant cells, human CD68(+) macrophages, and high bacilli numbers surrounded by a layer of CD3(+) T cells and a fibrotic response encapsulating the lesions were observed in livers and lungs from bacillus Calmette-Guérin-infected humanized mice but not in nonhumanized infected controls. Paradoxically, humanized mice contained higher mycobacterial numbers in organs than nonhumanized controls. The enhancement of bacterial load was mediated by human CD4(+) cells and associated to an increased expression of Programmed Death-1 protein and CD57 on T cells, molecules associated with inhibition and senescence. The lesions from mice depleted of CD4(+) cells were scarcer, minimal, and irregular compared with those from mice depleted of CD8(+) cells or nondepleted controls. Granulomas of bacillus Calmette-Guérin-infected humanized mice administered with a TNF-neutralizing TNF receptor fusion molecule preserved their structure, but contained higher levels of intracellular bacilli. Extended necrosis was observed in granulomas from M. tuberculosis- but not bacillus Calmette-Guérin-infected humanized mice. Our data indicate that humanized mice can be used as a model to study the formation and maintenance of human granuloma in tuberculosis and other infectious or noninfectious diseases.