pSS is an autoimmune disease common in middle-aged and elderly women that targets exocrine glands such as salivary glands and may involve multiple organs and systems. At present, many studies have shown that the proportion of immune cells in patients with pSS is different from that in normal people, which is also an important factor in the occurrence and aggravation of the disease. High-throughput analytical techniques such as transcriptomics and expression microarray analysis allow us to gain insight into changes in immune cell composition, and a unique feature of this study is the correlation of human gene expression data with those of Sjögren's syndrome-susceptible C57BL/6 Comprehensive analysis of the data. Allows us to characterize the cells in human and mouse models and may provide some insight into the mechanisms of pSS immune regulation.
In this study, in the human research, we downloaded the gene expression profile chip dataset of salivary glands of normal human and pSS patients from GEO, namely the GSE40611 dataset, used R package to rectify the data, and used CIBERSORT to analyze the data. Expression matrices of human immune cell subtypes were deconvoluted and finally plotted using R software. In mouse studies, we first constructed an ESS mouse model using homologous mouse salivary proteins that highly recapitulates the key features of human pSS, and identified changes in saliva volume and lymphocyte infiltration in salivary gland tissue. Determine the success of the model. Mouse salivary glands were collected and preserved during the process. After that, we used the collected mouse salivary gland tissue as a sample, sequenced the tissue by RNA-Seq technology, and the related sequencing results were processed by seq-ImmuCC, and R software was used to generate the required related charts to conduct a comprehensive analysis of the above data, Summarizing the cellular characteristics between the two has expanded a new horizon for the pSS-related regulatory mechanism.
In this study, through the analysis of immune infiltration, we found that mouse and human immune cells have certain common features. For human data, we found that T cells gamma delta and T cells CD4 naive was positively correlated with plasma cells, and we could find naive B cells naive, CD4 memory activated, T cells gamma delta was significantly increased. And Plasma cells, NK cells resting, Monocytes, the content decreased significantly. Furthermore, PCA results suggest that immune cell infiltration can be used to differentiate pSS patients from normal individuals. For mouse data analysis, we found that Macrophages were negatively correlated with B.Cells, Eosinophils, Monocytes, and the number of macrophages increased. The trend of CD4+ T cells, Monocytes, and B.cells decreased significantly.
B lymphocytes are generated by differentiation of hematopoietic stem cells, mature in the bone marrow, and finally activate in secondary lymphoid organs. It has been suggested that the increased frequency of autoreactive antibody expression by mature naive B cells and impaired peripheral B cell tolerance in patients with pSS may be involved in the pathogenesis of pSS . B10 cells are a subset of B cells that can produce IL-10, which play an important role in maintaining immune stability mainly through the negative immune regulation function of IL-10. In the process of inflammatory response, B10 cells affect the occurrence and development of pSS through multiple factors, such as inducing T cell anergy or Treg expansion during antigen presentation, or directly inhibiting Th1 and Th17 through IL-10 to alleviate the disease. Some studies have also found that B10 plays a key role in regulating Tfh cell responses. Adoptive transfer of B10 cells can effectively inhibit Tfh cell responses and attenuate the histopathological score of ESS mice . In sexually transmitted diseases, the frequency of cells is also significantly reduced, the inhibitory cytokines secreted by them are also reduced to a certain extent, and the number of B10 cells is negatively correlated with the progression of the disease. This is consistent with our finding that the number of naive B cells increased while the number of B cells decreased.
Macrophages are innate immune cells and play a myriad of important roles, such as host defense, tissue homeostasis, and regulation of inflammatory responses[22, 23]. Macrophages are innate immune cells and play a myriad of important roles, such as host defense, tissue homeostasis, and regulation of inflammatory responses. And macrophages are an important part of B cells. Many studies have shown that macrophages play an important role in the pathological damage of salivary and lacrimal glands. Macrophages in the salivary glands are obviously pathogenic and can secrete related cytokines, and patients with significant macrophage infiltration in the salivary glands have a higher degree of salivary gland swelling. This is consistent with the increased numbers of macrophages in our results.
CD8+ T lymphocytes are a complex group of lymphocytes with different phenotypes. Studies have shown that activated CD8+ T lymphocytes aggregate around apoptotic acinar epithelial cells, and CD8+ T cells infiltrating glands show cytotoxicity. Not affected by CD4+ T cells. it is worth noting that as the disease progresses, the proportion of CD8+ T cells in pSS patients is significantly increased compared with normal people, which is consistent with our results of. Memory CD4+ T cells are highly associated with autoimmune diseases due to their long-lived properties, efficient responses to antigens, and the potential to mediate recurrent autoimmune responses. However, many key questions about the potential contribution of memory CD4+ T cells to autoimmune disease remain unanswered. Some studies have shown that the relative proportion of memory CD4+ T in patients with pSS compared with normal controls is increased; this is consistent with our results of human immune infiltration, but the specificity of memory T cells and pSS is different. The interrelationships are still not fully understood. In addition, some scholars have found that the reduction of lymphocytes in pSS patients is related to the premature senescence of naive CD4+ T cells in the body, which also explains the reduction of CD4+ T lymphocytes in the mouse data . Determining the immunobiological roles of CD4+ T and CD8+ T cells in pSS is critical for the development of targeted therapies for pSS driven by CD4+ or CD8+ T cells. Gamma delta T cells (T cells gamma delta) are γ/δ+ T cells, accounting for about 2–5% of peripheral blood T lymphocytes, mainly distributed in mucosa-associated lymphoid tissues, and their immune functions are between innate immunity and adaptive immunity. Between immunity, plays a role in tissue homeostasis and infection monitoring . It has been reported that the proportion of activated cells in γ/δ+ T cell subsets in peripheral blood of pSS patients is significantly higher than that of controls, and the frequency of activated cells is related to the disease course of pSS patients , which is consistent with our results. Consistently, this suggests that this T cell subset may play a role in the pathological immune response encountered in pSS.
On the other hand, monocytes have been studied relatively less than lymphocytes, but they are known to be involved in the pathogenesis of pSS. Indeed, expanding data suggest that infiltrating monocytes and macrophages are phenotypically altered in autoimmune disease and have been implicated in both mice and humans[33, 34]. In humans, monocytes are divided into three subtypes, "classical" monocytes, "intermediate" monocytes, and "pro-inflammatory", based on the relative surface expression of the lipopolysaccharide (LPS) coreceptor CD14 and the FCγIII receptor CD16 monocytes. Several reports suggest that the primary function of most circulating monocytes is the phagocytosis of cellular debris, pathogens, and other external factors[35, 36], in a manner that does not involve the release of inflammatory mediators; however, monocytes in patients with pSS have been observed Cells are inefficient in the clearance of apoptotic cells, which is also associated with the production of pro-inflammatory cytokines such as IL-6, TNF-α, IL-10, transforming growth factor (TGF)-β and interferon (IFN)- α[37–39].
However, the limitation of this study is that the seq-ImmuCC model only covers 10 cell types. For example, gamma delta T cells, which play an important role in the immune system, are not included, and further improvement is needed in the future. In addition, the human part is based on bioinformatic immune infiltration analysis of transcriptomic signatures from public datasets, which may not correspond to the actual situation, and further studies are needed to confirm the findings observed in human biopsies.