In situ analysis of lung antigen‐presenting cells during murine pulmonary infection with virulent Mycobacterium tuberculosis

Abstract

Scarce information exists about the role of lung antigen-presenting cells (APCs) in vivo during pulmonary tuberculosis. As APCs activate cellular immunity, following intratracheal inoculation with virulent Mycobacterium tuberculosis, we assessed in situ lung APC recruitment, distribution, granuloma involvement, morphology and mycobacterial burden by using MHC-CII, CD14, scavenger receptor class A (SRA), the murine dendritic cell (DC)-restricted marker CD11c and Ziehl-Neelsen staining. CD11c(+) DC and CD14(+) cell recruitment into lungs appeared by day 14, continuing until day 60. MHC-CII(+) cells increased since day 7, persisting until day 60. Thus, virulent mycobacteria delays (14-21 days) lung APC recruitment compared to model antigens and nonvirulent bacilli (24-48 h). Regarding granuloma constitution, highly bacillary CD14(+) and SRA(+) cells were centrally located. MHC-CII(+) cells were more peripheral, with less mycobacteria. CD11c(+) cells were heterogeneously distributed within granulomas, with scarce bacilli. When labelling lung suspensions for MHC-CII and classifying cells as macrophages or DC, then staining for Ziehl-Neelsen, a remarkable segregation was found regarding bacillary burden. Most macrophage-like cells contained numerous bacilli, while DC had no or scarce mycobacteria. This implies differential APC contributions in situ during pulmonary tuberculosis regarding mycobacterial uptake, granuloma involvement and perhaps bacillary growth.

Partial Redundancy of the Pattern Recognition Receptors, Scavenger Receptors, and C-Type Lectins for the Long-Term Control of Mycobacterium tuberculosis Infection

“…1). This is in agreement with the strong SR-A upregulation reported 3-9 wk after M. tuberculosis infection in mice (56), as well as in human pulmonary macrophages from tuberculosis patients (57). However, MARCO expression was not affected 1-4 wk after M. tuberculosis infection in our model (Supplemental Fig.…”

In Vivo Role of Dendritic Cells in a Murine Model of Pulmonary Cryptococcosis

“…Our data showed that the percentage of CD11c ϩ DC in the lungs increased throughout infection, suggesting that there was DC infiltration into the lungs during infection. DC infiltration into the lungs has also been reported with other proinflammatory stimuli in the lung, including gamma interferon (27), cigarette smoking (73), and allergen inhalation (53,54), as well as during bacterial and viral infections (53,54,62). Also, the percentage of the lung DC that expressed the maturation marker CD80 significantly increased, and the levels of CD86 and MHC-II increased moderately throughout the course of the infection, suggesting that pulmonary cryptococcal infection leads to DC maturation.…”

“…By examining confocal images, we determined that the C. neoformans cells were indeed inside the DC. In studies of other pathogens that infect the lung, such as M. tuberculosis (28,62,64,66) and A. fumigatus (11), lung DC have been shown to phagocytose the organisms in vivo and are responsible for initiating an adaptive immune response. Moreover, we have shown previously that DC phagocytose C. neoformans in vitro when it is opsonized by complement or antibody (38).…”

“…However, it is not known whether DC in the lung phagocytose C. neoformans and are capable of inducing protective immunity in an in vivo infection model. For other pulmonary pathogens, including Mycobacterium tuberculosis (28,62,64) and Aspergillus fumigatus (11), lung DC are important for phagocytosis and for initiating an adaptive immune response.…”

The Pathology ofMycobacterium tuberculosisInfection

“…13,89 Dendritic cells infected with Mtb have an impaired ability to present lipid antigens, possibly due to delay of maturation mediated by cell wall components, and are retained at the lung for prolonged periods compared to DCs that have taken up model antigens. 163 Interestingly, it has been shown in vitro that more virulent strains of Mtb, the Beijing strains in particular, inhibit the maturation of DCs and the ability of DCs to present lipid antigens through decreased expression of CD1. 192 The activated T cells specific for mycobacterial antigens migrate to the lungs to participate in granuloma formation.…”