Periodic Reporting for period 4 - GutBCells (Cellular Dynamics of Intestinal Antibody-Mediated Immune Response)
Reporting period: 2020-11-01 to 2021-04-30
Our immune system clears invading pathogens through the activation of immune cells that recognize pathogen-derived signals. An additional role of the immune system is to provide long-lasting protective memory to avoid additional microbe invasions upon exposure to the same pathogen. Antibodies play a critical role in the establishment of long-lasting immunity. The generation of antibody-forming cells depends on the exchange of information between different cell types in specialized immune niches within lymph nodes. In these microanatomical sites, the precursors of antibody-forming cells respond to pieces of the pathogenic microbe or vaccine agents. The responding cells express on their surface an antibody that can recognize specifically the stimulating pathogen or vaccine and differentiate into antibody-forming cells. Whereas this process was extensively studied in the context of immune responses in peripheral lymph nodes in response to invading microbes and vaccination, less was known about how antibodies emerge in gut lymphoid organs. These are specialized structures that are scattered throughout the small intestine and host the precursors of antibody-forming cells and also supporting immune cells. As opposed to typical lymph nodes, the gut lymphoid organs have a different structure and they do not passively drain antigens from tissues as occurs in typical lymph.
In the current ERC-funded study we examined how antibody-mediated immune responses emerge in gut lymphoid organs and whether the same steps occur as those described for immune responses in peripheral lymph nodes. Since gut lymph nodes have an unconventional structure and host unique immunological niches we developed advanced imaging approaches in order to visualize them. This technique allows the visualization of all the immunological niches in intact organs and the detection of rare cells that respond to oral vaccination or a pantheon. Using this approach we show that precursors of antibody-forming cells encounter the vaccine or antigens in a unique niche with gut lymph nodes that are located close to the gut lumen. Followed initial activation, the immune cells transit to a different immunological niche where a selection of immune cells that express high-affinity protective antibodies takes place. We demonstrated that antibody affinity has no role in the niche where immune cell interacts with microbe-derived antigen, however, only cells that carry high-affinity antibodies progress to the next niche. We have identified the regulatory cells within the activation niche that controls immune cell expansion and allow the transit to the second niche. Furthermore, we show that the molecular mechanisms that control immune cell translocation between niches and cell-cell interaction in the gut are not necessarily similar to the one described in lymph nodes. Accordingly, we found that transgenic mice that are unable to support antibody immune response in peripheral lymph nodes can generate antibodies in the gut. Collectively, through the development of new imaging approaches, we have uncovered the cellular dynamics and molecular regulation that mediate antibody-mediated immune responses in the gut. These events are not similar to those that occur in peripheral lymph nodes. Understanding how antibodies are generated in the gut is expected to lead to better design of oral vaccinations.
In the current ERC-funded study we examined how antibody-mediated immune responses emerge in gut lymphoid organs and whether the same steps occur as those described for immune responses in peripheral lymph nodes. Since gut lymph nodes have an unconventional structure and host unique immunological niches we developed advanced imaging approaches in order to visualize them. This technique allows the visualization of all the immunological niches in intact organs and the detection of rare cells that respond to oral vaccination or a pantheon. Using this approach we show that precursors of antibody-forming cells encounter the vaccine or antigens in a unique niche with gut lymph nodes that are located close to the gut lumen. Followed initial activation, the immune cells transit to a different immunological niche where a selection of immune cells that express high-affinity protective antibodies takes place. We demonstrated that antibody affinity has no role in the niche where immune cell interacts with microbe-derived antigen, however, only cells that carry high-affinity antibodies progress to the next niche. We have identified the regulatory cells within the activation niche that controls immune cell expansion and allow the transit to the second niche. Furthermore, we show that the molecular mechanisms that control immune cell translocation between niches and cell-cell interaction in the gut are not necessarily similar to the one described in lymph nodes. Accordingly, we found that transgenic mice that are unable to support antibody immune response in peripheral lymph nodes can generate antibodies in the gut. Collectively, through the development of new imaging approaches, we have uncovered the cellular dynamics and molecular regulation that mediate antibody-mediated immune responses in the gut. These events are not similar to those that occur in peripheral lymph nodes. Understanding how antibodies are generated in the gut is expected to lead to better design of oral vaccinations.
We have studied how the antibody immune response emegre in the gut using primarily imaging approaches. Through the development of new techniques to visualize the immune system we have made new discoveries and substantially increased our understanding of how antibodies form in mucosal tissues.
Aim 1: We used two imaging approaches to identify immune cells in the unique immunological niches of the gut. First, we designed a new technique that links location with cell identity and transcriptome. We labeled immune niches within lymph nodes using light (photoactivation) and then dissected specifically the labeled cells for surface marker and gene expression analysis. Using this approach we have identified a specific subset of immune cells that oversee the generation of antibodies in the gut lymph nodes.
Aim 2: In aim two we examined the dynamics of the immune response within gut lymph nodes. For this purpose, we developed an imaging approach that allowed us to visualize multiple immune niches in intact lymphoid organs. This approach allowed us to detect the location of the immune cells and track their transition between niches. We found that in order to move between specific microanatomical sites, immune cells need to express high-affinity antibodies on their surface. Moreover, through tracking the movement of the cells we could determine that the B cell immune response in the gut follows different stages compared to the immune response in peripheral lymph nodes. Specially, we showed that antibody affinity determines immune cell translocation between niches.
Aim 3: In this aim, we examined the dynamics of antibody-forming cell generation in the gut lymph nodes. We discovered a new subset of plasma cells that exist only in the gut lymph nodes. These cells form in a niche where interaction with antigen takes place. We are still characterizing these cells using transcriptomic and microscopy approaches.
Aim 4: lastly, we examined how antibody-immune response to the microbiome is modulated in the gut. We found that a critical mechanism required for the immune response in the periphery is dispensable in gut lymph nodes. These results showed for the first time that some of the basic molecular mechanisms function differently in the gut and periphery.
Aim 1: We used two imaging approaches to identify immune cells in the unique immunological niches of the gut. First, we designed a new technique that links location with cell identity and transcriptome. We labeled immune niches within lymph nodes using light (photoactivation) and then dissected specifically the labeled cells for surface marker and gene expression analysis. Using this approach we have identified a specific subset of immune cells that oversee the generation of antibodies in the gut lymph nodes.
Aim 2: In aim two we examined the dynamics of the immune response within gut lymph nodes. For this purpose, we developed an imaging approach that allowed us to visualize multiple immune niches in intact lymphoid organs. This approach allowed us to detect the location of the immune cells and track their transition between niches. We found that in order to move between specific microanatomical sites, immune cells need to express high-affinity antibodies on their surface. Moreover, through tracking the movement of the cells we could determine that the B cell immune response in the gut follows different stages compared to the immune response in peripheral lymph nodes. Specially, we showed that antibody affinity determines immune cell translocation between niches.
Aim 3: In this aim, we examined the dynamics of antibody-forming cell generation in the gut lymph nodes. We discovered a new subset of plasma cells that exist only in the gut lymph nodes. These cells form in a niche where interaction with antigen takes place. We are still characterizing these cells using transcriptomic and microscopy approaches.
Aim 4: lastly, we examined how antibody-immune response to the microbiome is modulated in the gut. We found that a critical mechanism required for the immune response in the periphery is dispensable in gut lymph nodes. These results showed for the first time that some of the basic molecular mechanisms function differently in the gut and periphery.
Aim 1. We developed two imaging approaches. Whole organ imaging that allows visualisation of all the immune niches and the Niche-Seq for analysis of cell composition and their transcriptome in a niche.
These approaches lead to discovery of cell subsets and their dynamics in immune organs in the gut. Furthermore, these techniques are now used in the lab to support multiple new projects that involve patio temporal changes.
Aim 2. Using the approaches developed in Aim 1. We obtained deep understanding of the cell dynamics in the gut and discovered the role of antibody affinity during oral vaccination.
Aim 3. We discovered a new antibody forming cell type in that exist only in the gut. We defined the location of this cell in the gut and which other cell types and signals control its formation.
Aim 4. We found that a basic mechanism that functions in the periphery is not entirely necessary to form an immune response in the gut. Under this aim we have established the concept that different events and molecular mechanisms control immune responses in gut lymph nodes.
These approaches lead to discovery of cell subsets and their dynamics in immune organs in the gut. Furthermore, these techniques are now used in the lab to support multiple new projects that involve patio temporal changes.
Aim 2. Using the approaches developed in Aim 1. We obtained deep understanding of the cell dynamics in the gut and discovered the role of antibody affinity during oral vaccination.
Aim 3. We discovered a new antibody forming cell type in that exist only in the gut. We defined the location of this cell in the gut and which other cell types and signals control its formation.
Aim 4. We found that a basic mechanism that functions in the periphery is not entirely necessary to form an immune response in the gut. Under this aim we have established the concept that different events and molecular mechanisms control immune responses in gut lymph nodes.