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Splenic Macrophage Subsets and Their Function during Blood-Borne Infections.

Borges da Silva H, Fonseca R, Pereira RM, Cassado Ados A, Álvarez JM, D'Império Lima MR - Front Immunol (2015)

Bottom Line: Marginal metallophilic macrophages (MMMΦs) and marginal zone macrophages (MZMΦs) are cells with great ability to internalize blood-borne pathogens such as virus or bacteria.Their localization adjacent to T- and B-cell-rich splenic areas favors the rapid contact between these macrophages and cells from adaptive immunity.Indeed, MMMΦs and MZMΦs are considered important bridges between innate and adaptive immunity.

View Article: PubMed Central - PubMed

Affiliation: Department of Immunology, Instituto de Ciências Biomédicas, Universidade de São Paulo , São Paulo , Brazil.

ABSTRACT
The spleen is one of the major immunological sites for maintaining blood homeostasis. Previous studies showed that heterogeneous splenic macrophage populations contribute in complimentary ways to control blood-borne infections and induce effective immune responses. Marginal metallophilic macrophages (MMMΦs) and marginal zone macrophages (MZMΦs) are cells with great ability to internalize blood-borne pathogens such as virus or bacteria. Their localization adjacent to T- and B-cell-rich splenic areas favors the rapid contact between these macrophages and cells from adaptive immunity. Indeed, MMMΦs and MZMΦs are considered important bridges between innate and adaptive immunity. Although red pulp macrophages (RpMΦs) are mainly considered scavengers for senescent erythrocytes, several data indicate a role for RpMΦs in control of infections such as blood-stage malaria as well as in the induction of innate and adaptive immunity. Here, we review current data on how different macrophage subsets recognize and help eliminate blood-borne pathogens, and, in turn, how the inflammatory microenvironment in different phases of infection (acute, chronic, and after pathogen clearance) influences macrophage function and survival.

No MeSH data available.


Related in: MedlinePlus

Role of MZMΦs and MMMΦs during infection. In this figure, a brief description on how MZMΦs and MMMΦs are able to recognize and mediate protection against blood-borne pathogens is shown. MZMΦs (above) can recognize bacterial and viral infections by receptors such as MARCO or SIGNR1, which usually induce internalization and further pathogen degradation. A similar feature can be depicted for MMMΦs, where MOMA-1 or SIGLEC can mediate pathogen recognition and elimination from circulation. MMMΦs can also interact with CD8α+ dendritic cells (DCs), which ultimately lead to CD8+ T-cell activation.
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Figure 3: Role of MZMΦs and MMMΦs during infection. In this figure, a brief description on how MZMΦs and MMMΦs are able to recognize and mediate protection against blood-borne pathogens is shown. MZMΦs (above) can recognize bacterial and viral infections by receptors such as MARCO or SIGNR1, which usually induce internalization and further pathogen degradation. A similar feature can be depicted for MMMΦs, where MOMA-1 or SIGLEC can mediate pathogen recognition and elimination from circulation. MMMΦs can also interact with CD8α+ dendritic cells (DCs), which ultimately lead to CD8+ T-cell activation.

Mentions: Marginal zone macrophages and MMMΦs are fundamental in the early control of Listeria monocytogenes bacteremia, as evaluated by depletion of these MΦs using a low dose of clodronate liposomes (65). T-cell responses are not affected in this experimental model, ruling out the participation of MZMΦs and MMMΦs as antigen-presenting cells. Similar findings were reported during infection with Neisseria meningitidis (64), thus it is likely that these MΦs have a direct role in the elimination of bacteria from circulation. Conversely, adenoviruses colocalize with MZMΦs as soon as a few minutes after intravenous injection in mice (66). MZMΦs and MMMΦs play a similar role in lymphocytic choriomeningitis virus (LCMV) infection, corroborating the importance of these MΦs in first-line antiviral defense (67). On the other hand, localization of MZMΦs and MMMΦs in the interface between the bloodstream and lymphocyte-rich zones makes them suitable to bridge innate and adaptive immunity in several situations. For instance, mice lacking SRs MARCO and SR-A1 show a defective microarchitecture of the splenic MZ and an impaired T-independent type 2 response when challenged with pneumococcal polysaccharide (68). MMMΦs also collaborate in cytotoxic T-cell activation by transferring antigen directly to CD8α+ DCs, which are specialized in cross-presentation to CD8+ T cells (69). This observation supports the use of the MMMΦs antigen-concentrating capacity in therapeutic strategies for the development of antitumor immunity. The different roles of MZMΦs and MMMΦs in blood-borne infections are shown in Figure 3.


Splenic Macrophage Subsets and Their Function during Blood-Borne Infections.

Borges da Silva H, Fonseca R, Pereira RM, Cassado Ados A, Álvarez JM, D'Império Lima MR - Front Immunol (2015)

Role of MZMΦs and MMMΦs during infection. In this figure, a brief description on how MZMΦs and MMMΦs are able to recognize and mediate protection against blood-borne pathogens is shown. MZMΦs (above) can recognize bacterial and viral infections by receptors such as MARCO or SIGNR1, which usually induce internalization and further pathogen degradation. A similar feature can be depicted for MMMΦs, where MOMA-1 or SIGLEC can mediate pathogen recognition and elimination from circulation. MMMΦs can also interact with CD8α+ dendritic cells (DCs), which ultimately lead to CD8+ T-cell activation.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4585205&req=5

Figure 3: Role of MZMΦs and MMMΦs during infection. In this figure, a brief description on how MZMΦs and MMMΦs are able to recognize and mediate protection against blood-borne pathogens is shown. MZMΦs (above) can recognize bacterial and viral infections by receptors such as MARCO or SIGNR1, which usually induce internalization and further pathogen degradation. A similar feature can be depicted for MMMΦs, where MOMA-1 or SIGLEC can mediate pathogen recognition and elimination from circulation. MMMΦs can also interact with CD8α+ dendritic cells (DCs), which ultimately lead to CD8+ T-cell activation.
Mentions: Marginal zone macrophages and MMMΦs are fundamental in the early control of Listeria monocytogenes bacteremia, as evaluated by depletion of these MΦs using a low dose of clodronate liposomes (65). T-cell responses are not affected in this experimental model, ruling out the participation of MZMΦs and MMMΦs as antigen-presenting cells. Similar findings were reported during infection with Neisseria meningitidis (64), thus it is likely that these MΦs have a direct role in the elimination of bacteria from circulation. Conversely, adenoviruses colocalize with MZMΦs as soon as a few minutes after intravenous injection in mice (66). MZMΦs and MMMΦs play a similar role in lymphocytic choriomeningitis virus (LCMV) infection, corroborating the importance of these MΦs in first-line antiviral defense (67). On the other hand, localization of MZMΦs and MMMΦs in the interface between the bloodstream and lymphocyte-rich zones makes them suitable to bridge innate and adaptive immunity in several situations. For instance, mice lacking SRs MARCO and SR-A1 show a defective microarchitecture of the splenic MZ and an impaired T-independent type 2 response when challenged with pneumococcal polysaccharide (68). MMMΦs also collaborate in cytotoxic T-cell activation by transferring antigen directly to CD8α+ DCs, which are specialized in cross-presentation to CD8+ T cells (69). This observation supports the use of the MMMΦs antigen-concentrating capacity in therapeutic strategies for the development of antitumor immunity. The different roles of MZMΦs and MMMΦs in blood-borne infections are shown in Figure 3.

Bottom Line: Marginal metallophilic macrophages (MMMΦs) and marginal zone macrophages (MZMΦs) are cells with great ability to internalize blood-borne pathogens such as virus or bacteria.Their localization adjacent to T- and B-cell-rich splenic areas favors the rapid contact between these macrophages and cells from adaptive immunity.Indeed, MMMΦs and MZMΦs are considered important bridges between innate and adaptive immunity.

View Article: PubMed Central - PubMed

Affiliation: Department of Immunology, Instituto de Ciências Biomédicas, Universidade de São Paulo , São Paulo , Brazil.

ABSTRACT
The spleen is one of the major immunological sites for maintaining blood homeostasis. Previous studies showed that heterogeneous splenic macrophage populations contribute in complimentary ways to control blood-borne infections and induce effective immune responses. Marginal metallophilic macrophages (MMMΦs) and marginal zone macrophages (MZMΦs) are cells with great ability to internalize blood-borne pathogens such as virus or bacteria. Their localization adjacent to T- and B-cell-rich splenic areas favors the rapid contact between these macrophages and cells from adaptive immunity. Indeed, MMMΦs and MZMΦs are considered important bridges between innate and adaptive immunity. Although red pulp macrophages (RpMΦs) are mainly considered scavengers for senescent erythrocytes, several data indicate a role for RpMΦs in control of infections such as blood-stage malaria as well as in the induction of innate and adaptive immunity. Here, we review current data on how different macrophage subsets recognize and help eliminate blood-borne pathogens, and, in turn, how the inflammatory microenvironment in different phases of infection (acute, chronic, and after pathogen clearance) influences macrophage function and survival.

No MeSH data available.


Related in: MedlinePlus