Limits...
Overexpression of Bovine FcRn in Mice Enhances T-Dependent Immune Responses by Amplifying T Helper Cell Frequency and Germinal Center Enlargement in the Spleen.

Schneider Z, Jani PK, Szikora B, Végh A, Kövesdi D, Iliás A, Cervenak J, Balogh P, Kurucz I, Kacskovics I - Front Immunol (2015)

Bottom Line: The neonatal Fc receptor (FcRn) plays key roles in IgG and albumin homeostasis, maternal IgG transport, and antigen presentation of IgG-opsonized antigens.Previously, we reported that transgenic (Tg) mice that overexpress the bovine FcRn (bFcRn) have augmented T-dependent humoral immune response with increased IgG protection, higher level of antigen-specific antibodies, greater number of antigen-specific B cells, and effective immune response even against weakly immunogenic epitopes.In the current study, we analyzed the localization of the bFcRn in secondary lymphoid organs, and focused to demonstrate the in vivo impact of its overexpression in the spleen on the course of antibody production. bFcRn was highly expressed by red pulp macrophages and marginal zone macrophages in the spleen and by subcapsular sinus macrophages and macrophage-like cells in the interfollicular areas in the lymph node cortex.

View Article: PubMed Central - PubMed

Affiliation: Department of Immunology, Eötvös Loránd University , Budapest , Hungary.

ABSTRACT
The neonatal Fc receptor (FcRn) plays key roles in IgG and albumin homeostasis, maternal IgG transport, and antigen presentation of IgG-opsonized antigens. Previously, we reported that transgenic (Tg) mice that overexpress the bovine FcRn (bFcRn) have augmented T-dependent humoral immune response with increased IgG protection, higher level of antigen-specific antibodies, greater number of antigen-specific B cells, and effective immune response even against weakly immunogenic epitopes. In the current study, we analyzed the localization of the bFcRn in secondary lymphoid organs, and focused to demonstrate the in vivo impact of its overexpression in the spleen on the course of antibody production. bFcRn was highly expressed by red pulp macrophages and marginal zone macrophages in the spleen and by subcapsular sinus macrophages and macrophage-like cells in the interfollicular areas in the lymph node cortex. We also demonstrated that splenic dendritic cells of Tg mice express bFcRn and intraperitoneal immunization of these mice with T-dependent antigens led to more than threefold increase in the number of antigen-specific activated T helper cells with increased size and numbers of germinal centers compared to wild-type controls. bFcRn expression in splenic B cells was also detected and that may also contribute to the enhanced B cell activation. Finally, we demonstrated that these Tg mice developed efficient immune response against very low dose of antigen, reflecting another important practical benefit of these Tg mice.

No MeSH data available.


Expression of FcRn in peripheral lymph nodes. mFcRn in wt lymph nodes (A,C,E) and bFcRn in Tg lymph nodes (B,D,F) show slightly different tissue distribution, where wt mice express mFcRn (green) only in the interfollicular region, whereas in Tg mice, substantial co-expression of bFcRn (green) is seen with the Sn/CD169+ subcapsular metallophilic MΦs (red, overlap seen as yellow, indicated with an arrow pointing at a group of double-positive cells in (F)]. The high power insets (E,F) correspond to the dotted rectangular area in the merged pictures scale (representative examples for a cohort n > 6, bar size: 100 μm).
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4507463&req=5

Figure 4: Expression of FcRn in peripheral lymph nodes. mFcRn in wt lymph nodes (A,C,E) and bFcRn in Tg lymph nodes (B,D,F) show slightly different tissue distribution, where wt mice express mFcRn (green) only in the interfollicular region, whereas in Tg mice, substantial co-expression of bFcRn (green) is seen with the Sn/CD169+ subcapsular metallophilic MΦs (red, overlap seen as yellow, indicated with an arrow pointing at a group of double-positive cells in (F)]. The high power insets (E,F) correspond to the dotted rectangular area in the merged pictures scale (representative examples for a cohort n > 6, bar size: 100 μm).

Mentions: Transgenic mice that overexpress the bFcRn carry five copies of a bovine genomic fragment, encoding the bFcRn α-chain (FCGRT) (6). Upon immunization, these animals launch an enhanced antibody response against a variety of T-dependent antigens with mechanisms, which have not been completely elucidated yet. To test whether the expression of transgene containing all regulatory elements of the bFcRn gene or its chromosomal integration influences the architecture of spleen, we compared the structure of the wt and Tg spleen using tissue immunofluorescence for lymphoid compartmentalization and the expression pattern of endogenous mFcRn and transgenic bFcRn, respectively. We found that the spleen of Tg mice showed normal T-, B cell, and marginal zone (MZ) compartmentalization indistinguishable from wt controls using Thy-1, B220, Gr1, or MadCAM-1-specific labeling (Figure 1). Similar results were obtained with animals immunized with TNP-KLH (data not shown). Next, we correlated the cell-type-specific expression of bFcRn to the mFcRn in the spleen and lymph nodes. mFcRn localization was performed by using a mFcRn-specific hamster antiserum that had been developed and validated previously (14); as negative control, we used non-specific hamster serum with the same secondary reagent and found no specific staining. For bFcRn detection, we used the bFcRn-specific mAb (Z15_6D5/8) that we recently developed and showed that it does not cross-react with the endogenous mFcRn (19) (Figures 2A–D). Staining of F4/80-positive red pulp MΦs revealed an expression pattern of bFcRn in Tg mice, which is similar to the mFcRn patterns in wt mice (Figures 2E–H) and supporting previous studies that indicated mFcRn expression in these cells (14). However, while mFcRn is clearly restricted to red pulp MΦs, bFcRn is, in addition, also strongly expressed in the MZ (Figure 3). This MZ display prompted us to perform a more detailed analysis of this compartment. Murine MZ harbors two distinct types of MZ MΦs, of which the metallophilic MΦs within the inner ring are identified by their Sn/CD169 expression, whereas the MZ MΦs located in the outer ring display MΦ receptor with collagenous structure (MARCO) (25). We found that both macrophage subsets display bFcRn in Tg mice. In contrast, no similar expression of mFcRn was detectable in either of these cell types (Figure 3). In peripheral lymph nodes, we observed both mFcRn and bFcRn staining in macrophage-like cells in the interfollicular areas of the lymph node cortex. In addition, we detected bFcRn expression in the CD169-positive, subcapsular sinus (SCS) MΦ, whereas mFcRn was not detected in these cells (Figure 4). These expressional patterns did not change after immunization (data not shown) and largely corroborate the previously reported analysis of the mFcRn expression in the spleen and lymph node (14) with the exception that we did not detect mFcRn in the MZ MΦ in the spleen or in SCS MΦ in lymph nodes of wt animals. These differences in staining pattern may perhaps be attributed to different protocols or reagents.


Overexpression of Bovine FcRn in Mice Enhances T-Dependent Immune Responses by Amplifying T Helper Cell Frequency and Germinal Center Enlargement in the Spleen.

Schneider Z, Jani PK, Szikora B, Végh A, Kövesdi D, Iliás A, Cervenak J, Balogh P, Kurucz I, Kacskovics I - Front Immunol (2015)

Expression of FcRn in peripheral lymph nodes. mFcRn in wt lymph nodes (A,C,E) and bFcRn in Tg lymph nodes (B,D,F) show slightly different tissue distribution, where wt mice express mFcRn (green) only in the interfollicular region, whereas in Tg mice, substantial co-expression of bFcRn (green) is seen with the Sn/CD169+ subcapsular metallophilic MΦs (red, overlap seen as yellow, indicated with an arrow pointing at a group of double-positive cells in (F)]. The high power insets (E,F) correspond to the dotted rectangular area in the merged pictures scale (representative examples for a cohort n > 6, bar size: 100 μm).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4507463&req=5

Figure 4: Expression of FcRn in peripheral lymph nodes. mFcRn in wt lymph nodes (A,C,E) and bFcRn in Tg lymph nodes (B,D,F) show slightly different tissue distribution, where wt mice express mFcRn (green) only in the interfollicular region, whereas in Tg mice, substantial co-expression of bFcRn (green) is seen with the Sn/CD169+ subcapsular metallophilic MΦs (red, overlap seen as yellow, indicated with an arrow pointing at a group of double-positive cells in (F)]. The high power insets (E,F) correspond to the dotted rectangular area in the merged pictures scale (representative examples for a cohort n > 6, bar size: 100 μm).
Mentions: Transgenic mice that overexpress the bFcRn carry five copies of a bovine genomic fragment, encoding the bFcRn α-chain (FCGRT) (6). Upon immunization, these animals launch an enhanced antibody response against a variety of T-dependent antigens with mechanisms, which have not been completely elucidated yet. To test whether the expression of transgene containing all regulatory elements of the bFcRn gene or its chromosomal integration influences the architecture of spleen, we compared the structure of the wt and Tg spleen using tissue immunofluorescence for lymphoid compartmentalization and the expression pattern of endogenous mFcRn and transgenic bFcRn, respectively. We found that the spleen of Tg mice showed normal T-, B cell, and marginal zone (MZ) compartmentalization indistinguishable from wt controls using Thy-1, B220, Gr1, or MadCAM-1-specific labeling (Figure 1). Similar results were obtained with animals immunized with TNP-KLH (data not shown). Next, we correlated the cell-type-specific expression of bFcRn to the mFcRn in the spleen and lymph nodes. mFcRn localization was performed by using a mFcRn-specific hamster antiserum that had been developed and validated previously (14); as negative control, we used non-specific hamster serum with the same secondary reagent and found no specific staining. For bFcRn detection, we used the bFcRn-specific mAb (Z15_6D5/8) that we recently developed and showed that it does not cross-react with the endogenous mFcRn (19) (Figures 2A–D). Staining of F4/80-positive red pulp MΦs revealed an expression pattern of bFcRn in Tg mice, which is similar to the mFcRn patterns in wt mice (Figures 2E–H) and supporting previous studies that indicated mFcRn expression in these cells (14). However, while mFcRn is clearly restricted to red pulp MΦs, bFcRn is, in addition, also strongly expressed in the MZ (Figure 3). This MZ display prompted us to perform a more detailed analysis of this compartment. Murine MZ harbors two distinct types of MZ MΦs, of which the metallophilic MΦs within the inner ring are identified by their Sn/CD169 expression, whereas the MZ MΦs located in the outer ring display MΦ receptor with collagenous structure (MARCO) (25). We found that both macrophage subsets display bFcRn in Tg mice. In contrast, no similar expression of mFcRn was detectable in either of these cell types (Figure 3). In peripheral lymph nodes, we observed both mFcRn and bFcRn staining in macrophage-like cells in the interfollicular areas of the lymph node cortex. In addition, we detected bFcRn expression in the CD169-positive, subcapsular sinus (SCS) MΦ, whereas mFcRn was not detected in these cells (Figure 4). These expressional patterns did not change after immunization (data not shown) and largely corroborate the previously reported analysis of the mFcRn expression in the spleen and lymph node (14) with the exception that we did not detect mFcRn in the MZ MΦ in the spleen or in SCS MΦ in lymph nodes of wt animals. These differences in staining pattern may perhaps be attributed to different protocols or reagents.

Bottom Line: The neonatal Fc receptor (FcRn) plays key roles in IgG and albumin homeostasis, maternal IgG transport, and antigen presentation of IgG-opsonized antigens.Previously, we reported that transgenic (Tg) mice that overexpress the bovine FcRn (bFcRn) have augmented T-dependent humoral immune response with increased IgG protection, higher level of antigen-specific antibodies, greater number of antigen-specific B cells, and effective immune response even against weakly immunogenic epitopes.In the current study, we analyzed the localization of the bFcRn in secondary lymphoid organs, and focused to demonstrate the in vivo impact of its overexpression in the spleen on the course of antibody production. bFcRn was highly expressed by red pulp macrophages and marginal zone macrophages in the spleen and by subcapsular sinus macrophages and macrophage-like cells in the interfollicular areas in the lymph node cortex.

View Article: PubMed Central - PubMed

Affiliation: Department of Immunology, Eötvös Loránd University , Budapest , Hungary.

ABSTRACT
The neonatal Fc receptor (FcRn) plays key roles in IgG and albumin homeostasis, maternal IgG transport, and antigen presentation of IgG-opsonized antigens. Previously, we reported that transgenic (Tg) mice that overexpress the bovine FcRn (bFcRn) have augmented T-dependent humoral immune response with increased IgG protection, higher level of antigen-specific antibodies, greater number of antigen-specific B cells, and effective immune response even against weakly immunogenic epitopes. In the current study, we analyzed the localization of the bFcRn in secondary lymphoid organs, and focused to demonstrate the in vivo impact of its overexpression in the spleen on the course of antibody production. bFcRn was highly expressed by red pulp macrophages and marginal zone macrophages in the spleen and by subcapsular sinus macrophages and macrophage-like cells in the interfollicular areas in the lymph node cortex. We also demonstrated that splenic dendritic cells of Tg mice express bFcRn and intraperitoneal immunization of these mice with T-dependent antigens led to more than threefold increase in the number of antigen-specific activated T helper cells with increased size and numbers of germinal centers compared to wild-type controls. bFcRn expression in splenic B cells was also detected and that may also contribute to the enhanced B cell activation. Finally, we demonstrated that these Tg mice developed efficient immune response against very low dose of antigen, reflecting another important practical benefit of these Tg mice.

No MeSH data available.