这一篇我们继续分析单细胞空间联合分析的文章，参考文章在Immunoglobulin-producing AT2-like cells secrete IgA into the extracellular matrix in pulmonary fibrosis，肺纤维化后免疫细胞反应的变化，其实越来越多的文章显示，单细胞空间的研究，更多注重于组织与免疫之间的关系。
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Abstract
Pulmonary fibrosis（肺纤维化） is an interstitial lung disease（间质性肺病） that can be caused by various factors. Here, we first observed extensive IgA deposition（沉积） in the extracellular matrix (ECM) of the lungs of mice with pulmonary fibrosis induced by silica inhalation（二氧化硅吸入，小鼠也是够可怜的）. Consistent with this phenomenon, spatial transcriptomic sequencing of fresh mouse lung tissues from control mice and model mice showed that transcripts were highly expressed in the lesion area(空间转录组描述疾病后的免疫变化). Single-cell RNA sequencing (scRNA-seq) and reconstruction of B cell receptor (BCR) sequences revealed a new cluster of cells with a shared BCR and high expression of genes related to immunoglobulin IgA production（单细胞 + BCR测序）. Surprisingly, these clonal cells had more characteristics of AT2 (alveolar epithelial cell type 2) cells than B cells; thus, these cells were named AT2-like cells. Therefore, we propose that secretion of IgA into the ECM by AT2-like cells is an important process that occurs during lung fibrosis（也就是说这篇文章主要是发现了这一现象）。
Main
Pulmonary fibrosis is a chronic progressive disease. The extracellular matrix (ECM), as the framework supporting lung tissue, is mainly composed of 5 types of substances, namely, collagen, noncollagen, elastin, proteoglycan and aminoglycan（细胞外基质（ECM）作为支撑肺组织的骨架，主要由胶原蛋白、非胶原蛋白、弹性蛋白、蛋白聚糖和氨基聚糖5种物质组成。）. These components are affected by lung cells and can in turn act on lung cells（这些成分受肺细胞影响，进而作用于肺细胞）. Lung epithelial injury and apoptosis（细胞凋亡） are thought to be the initiating factors of pulmonary fibrosis（内皮细胞损伤和凋亡是引起肺纤维化最初的影响因子）. To maintain the normal alveolar structure, lung epithelial progenitor cells proliferate and differentiate to replenish（补充） alveolar epithelial cells. In fact, abnormal and excessive proliferation of progenitor cells fails to restore normal structure, and these cells secret various cytokines that affect fibroblasts（事实上，祖细胞的异常和过度增殖无法恢复正常结构，这些细胞会分泌影响成纤维细胞的各种细胞因子 ）. In recent years, it has been reported that dysregulated repair and regeneration of epithelial cells is a driving factor of lung fibrosis; however, the specific molecular mechanism by which the epithelium communicates with other cells is still unclear（又是细胞通讯）。
In this study, we started with lung ECM proteomics（蛋白质组学） and found that IgA was the most highly deposited protein in the fibrotic lung ECM（这个地方倒是很值得研究）. To explore the source of IgA at the cellular and molecular levels, we applied spatial transcriptomics sequencing and single-cell sequencing to mouse lung tissue（单细胞空间联合分析）. By integrating proteomics and sequencing data, we found that AT2-like cells obviously proliferated in lungs with fibrosis induced by SiO2（这小鼠真的挺惨的）. Surprisingly, a cluster of AT2-like epithelial cells in fibrotic lungs shared the same BCR made up of , which was exactly consistent with the immunoglobulin IgA deposited in lung ECM from fibrotic lungs(令人惊讶的是，纤维化肺中的一组 AT2 样上皮细胞共享由
组成的相同 BCR，这与纤维化肺沉积在肺 ECM 中的免疫球蛋白 IgA 完全一致 ). It has been reported that IgA is distributed on the surface of the mucosal membrane of the respiratory tract(呼吸道粘膜) and promotes pulmonary fibrosis by activating fibroblasts(通过激活成纤维细胞促进肺纤维化). However, in our study, we found that a large amount of immunoglobulin IgA was deposited in fibrotic lung ECM. This is the first report in the world that epithelial cells, but not B cells, produce immunoglobulin during pulmonary fibrosis(上皮细胞产生免疫球蛋白，讲道理，有点颠覆的意味). We believe that this phenomenon is closely related to the occurrence of pulmonary fibrosis. Blocking AT2-like cells secreting IgA may be a potential way to treat pulmonary fibrosis.（基因敲除，这个临床运用也很难）。
Results
A large amount of immunoglobulin IgA is deposited in the lung ECM of mice with SiO2-induced fibrosis
Pneumoconiosis(尘肺) is a type of pulmonary fibrosis caused by inhalation of free silica（吸入游离二氧化硅）. Here, we established a lung fibrosis model through intratracheal instillation of a silica suspension (50 mg/ml, 100 μl) (SiO2 group); the control group received normal saline (NS group). The CT and H&E staining results showed that acute inflammation(急性炎症) was observed seven days after instillation, and collagen deposition(胶原沉积) was observed in the lungs 28 days after instillation, consistent with previous studies using this model. At 56 days after instillation, the levels of several indicators of pulmonaryfunction, including FEV75, IC and MMEF, were decreased. In addition to increased lung coefficients (lung weight/mouse body weight), strip- or sheet-like high density in CT and collagen deposition were observed by Sirius red staining in the SiO2-56d group compared to the NS-56d group. Therefore, we considered mice to have entered the fibrosis stage at 56 days after instillation of the SiO2 suspension(我们认为小鼠在滴注 SiO2 悬浮液后 56 天进入纤维化阶段).
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To explore the ECM components of fibrotic lungs, we generated a decellularized lung matrix(去细胞肺基质) from NS-56d (n=3) and SiO2-56d (n=3) samples and analysed the protein components through mass spectrometry(质谱)-based proteomics. All 6 specimens showed similar results, and the 3 NS-56d samples and the 3 SiO2-56d samples were most similar to each other. Ultimately, we identified 143 proteins with upregulated expression and 127 proteins with downregulated expression in the SiO2-56d group compared to the NS-56d group.(差异分析无处不在)。
IgA was identified as the most highly upregulated protein. Moreover, of the top 20 proteins with upregulated expression, the surfactant proteins SFTPB, SFTPD and SFTPA are canonically thought to be secreted by mature AT2 cells（表面活性蛋白 SFTPB、SFTPD 和 SFTPA 通常被认为是由成熟的 AT2 细胞分泌的）. Western blotting analysis confirmed that the IgA and SFTPB levels were substantially upregulated in the ECM of the SiO2-56d samples. The deposition of IgA is accompanied by the deposition of surfactant protein, suggesting that IgA may be related to AT2（IgA的沉积伴随着表面活性蛋白的沉积，提示IgA可能与AT2有关）. Gene Ontology (GO) analysis（富集分析） of upregulated proteins of SiO2-56d samples identified lysosome, alveolar lamellar body, secretory IgA immunoglobulin complex, and immunoglobulin receptor binding as enriched terms. The chordal graph（弦图） shows that the upregulated proteins are related to extracellular regions and membrane attack complexes（上调的蛋白质与细胞外区域和膜攻击复合物有关）. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis revealed related pathways, such as rheumatoid arthritis, systemic lupus erythematosus, and intestinal immune network for IgA production. In summary, these results indicated that lung fibrosis was closely associated with immunoglobulin production and AT2 cell activity（这些结果表明肺纤维化与免疫球蛋白的产生和 AT2 细胞活性密切相关）
To further explore the spatiotemporal characteristics of transcription in our lung fibrosis model, we performed spatial transcriptomic sequencing of four samples（空间转录组） (NS-7d, SiO2-7d, NS-56d, and SiO2-56d). Before sequencing, all mice were scanned by computed tomography (CT) , and both the SiO2-7d and SiO2-56d mice exhibited hyperdense areas on their lungs, indicating that the models were successfully established. To obtain transcripts from the same structures and eliminate potential confounding by differences in anatomical position, we collected the left lung from each mouse and sliced it in the horizontal direction（为了获得相同结构的转录本并消除解剖位置差异造成的潜在混淆，我们收集了每只小鼠的左肺并在水平方向切片，相同的切片位置，这个空间转录组的设计还是很不错的）. Then, we observed the tissue under a microscope. If the hilum of the lung and left main bronchus were observed, the tissue section was mounted onto the spatial transcriptomics arrays. In this way, we obtained four slices (one per experimental group) with approximately the same shape and anatomical location, with the major vessels and hilum of the lung clearly visible. H&E staining showed that the alveoli of the NS-7d and NS-56d samples had a normal structure, with no infiltration of inflammatory cells. For the SiO2-7d sample, many inflammatory cells had accumulated, and the alveolar structures were completely destroyed. For the SiO2-56d sample, infiltration of inflammatory cells was still detected but was weaker than that in the SiO2-7d sample, and some alveoli were filled with neutrophils. This indicates that the SiO2-7d and SiO2-56d mouse models were successfully established（这小鼠真的挺惨的）
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After establishing the basic histology of the lung sections from each group, we performed spatial transcriptomic sequencing according to the experimental procedures recommended by 10x Genomics and obtained a total of 6778 spots (a single spot can hold cells within 60 μm in diameter)（10X的空间技术）. The numbers of genes and unique molecular identifiers (UMIs) detected in the tissue sections of model mice was obviously greater than that of control mice. Then, we performed graph-based clustering, and we captured 11 clusters of spots（空间spot聚类）. The NS-7d and NS-56d samples were highly consistent in terms of gene number and clusters of spots(平行样本间的聚类结果很相近). The SiO2-7d and SiO2-56d samples were significantly different from their respective control samples in terms of spot clustering, and they were also significantly different from each other（SiO2-7d 和 SiO2-56d 样品在斑点聚类方面与各自的对照样品有显著差异，彼此之间也有显著差异 ）. These findings indicate that mRNA expression at the same anatomical location changed substantially from the inflammatory stage (7d) to the fibrosis stage (56d).（变化还挺大）
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- 注：a, UMAP graph of spots coloured by four samples. b, Clusters of spatial transcriptome spots on UMAP: 11 clusters in total, labelled in different colours. c. UMAP graph of individual sample, separated from (b). d, Clusters of spatial transcriptome spots shown in the tissue space
and
, inflammatory factors, were highly expressed in SiO2-7d lesions but showed decreased expression in SiO2-56d lesions. In terms of the expression of specific genes,
and
were highly expressed in SiO2-56d lesions, consistent with the observed high expression of the IgA protein. In addition, the expression of genes encoding immunoglobulin light chains, such as
and
, was highly expressed in SiO2-56d lesions. Combined with proteomic findings for the lung ECM, these results indicated a strong relationship between immunoglobulin expression IgA and lung fibrosis.(这些结果表明免疫球蛋白表达 IgA 与肺纤维化之间存在密切关系。)
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Single-cell sequencing detected highly amplified AT2-like cells in the SiO2-56d sample(单细胞技术)
To identify the cellular origin of IgA, we obtained whole lungs from four mice (NS-7d, SiO2-7d, NS-56d, and SiO2-56d, model time and groups were consistent with those used for spatial transcriptomic sequencing) and performed scRNA-seq（单细胞技术识别目标细胞的来源）. All mice were scanned by CT prior to tissue collection to confirm effective modelling. After scRNA-seq, the numbers of UMIs and genes were evaluated, and a total of 43,397 cells were obtained for data analysis. We normalized the transcriptomic data from the four groups and then applied graph-based clustering to the combined cells from all groups to analyse and compare the samples, which yielded 24 cell clusters（单细胞的常规分析）. We then annotated the cell type for each cluster according to canonical cell markers（依据传统的细胞marker来定义细胞类型） from Cell Marker and assigned these 24 clusters to 15 types of cells, including endothelial cells, monocytes, macrophages, dendritic cells, B cells, T cells, Ccl3- Ccl4- neutrophils, Ccl3+ Ccl4+ neutrophils, fibroblasts, AT2-like cells (cluster 1, cluster 3, cluster 15), red blood cells, and AT1 cells. The marker genes of the different cell types are shown in the uniform manifold approximation and projection (UMAP) diagram. To explore the cell compositions of the different samples, we calculated the relative percentages of the main 15 cell types in the four samples（每种细胞类型在各个样本中的占比）. The relative percentage of macrophages in the SiO2-7d sample was obviously increased compared to NS-7d, representing up to 18% of the total number of cells, and the percentage remained higher than that in the NS-56d sample, even in the SiO2-56 sample, indicating that macrophages were major participants in the inflammatory stage and were still present in the fibrotic stage. GO and KEGG analyses of differentially expressed genes (DEGs) of macrophages identified genes classically involved in the development of silicosis. Ccl3+ Ccl4+ Neutrophils, which are often involved in various inflammatory reactions induced by bacteria, viruses, and foreign objects, were activated upon stimulation with silica after 7 days and were detected until day 56.
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Because cells of clusters 1, 3, and 15 expressed Sftpc, Sftpb and Sftpa1, we identified the three clusters as AT2-like cells(目标细胞的识别). The proportion of AT2-like clusters 1 and 15 both showed an increase, but cluster 15 had far fewer cells than cluster 1. Interestingly, the proportion of AT2-like cluster 1 cells in the SiO2-56d sample was notably increased, reaching 40%. GO and KEGG analyses of up-regulated genes (Fc>2, p<0.05) of AT2-like cluster 1 cells indicated that they were enriched in immune-related terms, such as systemic lupus erythematosus; immunoglobulin complex, circulating; humoural immune response; and immunoglobulin production . Thus, we hypothesized that AT2-like cluster 1 plays an important role during the fibrosis stage.(群1起到了关键作用)
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Immunoglobulin-producing AT2-like cluster 1 cells have more characteristics of AT2 cells than B cells
To gain further insight into the function of cluster 1, we focused on the DEGs in this cluster compared with all other cell clusters（这种找差异基因的方式就是我们普通的方式）. We found that ,
and
were the top 3 DEGs in AT2-like cell cluster 1 . All three belong to the V gene group, with
and
encoding the mouse immunoglobulin light chain and
encoding the heavy chain(这个地方的方法大家要多多注意). Furthermore, all three genes were expressed at high levels in the SiO2-56d sample and were mainly expressed in cluster 1 cells. Moreover,
was verified to be highly expressed in cluster 1 in this sample, consistent with the observed high levels of IgA deposition.
These genes code for immunoglobulin and are thought to be expressed by B cells. To ensure that cluster 1 was not B cells, we analysed the expression of several B cell marker gene distributions in all the clusters by Loupe Brower 4.0(使用loupe查看). B cell marker genes such as Cd79a, Cd79b and Cd19（B细胞常用的marker大家都应该知道） were relatively highly expressed in the noted B cells. However, in the sections, no visible differences in the expression of these genes were observed between the SiO2-7d and NS-56d or SiO2-56d and NS-56d samples. This phenomenon indicated that B cells did not play a major role in the disease. In contrast, genes encoding AT2 markers such as Sftpc, Sftpa1 and Sftpb were relatively highly expressed in cluster 1 and showed significantly upregulated expression in the SiO2-7d and SiO2-56d sections. Scgb3a1 and Scgb3a2, markers of secretory epithelial or Clara cells (the progenitor cell of AT2), were both expressed in AT2-like cluster 1 cells. Spatially, they were expressed in the trachea(在空间上，它们在气管中表达). As these five genes (Sftpa1, Sftpb, Sftpc, Scgb3a1 and Scgb3a2) showed relatively higher expression in cluster 1, our findings suggested that cluster 1 cells originated from bronchial epithelial cells.(由于这五个基因（Sftpa1、Sftpb、Sftpc、Scgb3a1 和 Scgb3a2）在cluster 1 中表现出相对较高的表达，我们的研究结果表明cluster 1 细胞起源于支气管上皮细胞,上皮细胞在行使B细胞该有的免疫功能)。
Furthermore, of the five genes, Sftpa1, Sftpb and Sftpc were more likely to be activated in the SiO2-56d sample than in the NS-56d sample Simultaneous examination of the expression of and cell markers of AT2 or Clara cells revealed that more than half of the
cells coexpressed Sftpc (AT2 cell marker) or Scgb3a1 (Clara cell marker), but few coexpressed Cd79a or Cd19. This result strongly suggested that these
cells were likely not derived from B cells. Based on the analysis results, we speculated that cluster 1 represents a specialized type of AT2 cell (alveolar epithelial cell type 2). In other words, silica inhalation could trigger the transformation of normal AT2 cells into
AT2-like cells, which can transcribe BCR genes.(吸入二氧化硅可以触发正常的 AT2 细胞转化为
AT2 样细胞，后者可以转录 BCR 基因)
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BCR clonal expansion in the SiO2-56d sample
Because we observed the differential expression of the gene encoding the immunoglobulin light chain in the SiO2-56d sample, we wanted to further explore the usage of the V(D)J and C genes of BCR in the four samples. We reconstructed BCR sequences from scRNA sequencing. Across the four groups, several V genes, including ,
,
,
and
, were found at notably higher frequencies in the SiO2-56d sample. Among these five genes,
,
, and
were categorized as highly expressed DEGs in AT2-like cell cluster 1(再次证明了上皮细胞行使B细胞的功能).
and
were also mainly expressed in AT2-like cell cluster 1. Among IGH C genes, the expression of
was substantially increased in the SiO2-56d sample compared with the other three samples, which also indirectly led to a decline in the proportion of
and
usage. There was no obvious difference in the usage of other BCR genes across the four samples.
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On the basis of traditional immunology theory, we believe that clonal expansion is closely related to disease progression(基于传统免疫学理论，我们认为克隆扩增与疾病进展密切相关). According to an analysis of the top 30 clonotypes from each sample, we found no identical clonal expansions among the four samples(有点尴尬啊). A heat map composed of different V-J gene pairing frequencies showed 9 kinds of V-J gene combinations in the SiO2-56d sample in clonal populations that had expanded to over 100 cells. In the SiO2-56d sample, clonotypes comprising over 100 cells constituted more than 75% of the total clonal cell population, and approximately 75% of the total clonal cells came from AT2-like cluster 1. Combined with the scRNA sequencing information, these results showed that BCR genes were expressed not only in B cells but also in AT2-like cluster 1 cells（结合scRNA测序信息，这些结果表明BCR基因不仅在B细胞中表达，而且在AT2样cluster 1细胞中也有表达）. In fact, more BCR+ cells were identified as AT2-like cluster 1 cells. As with BCR, at least half of the clonal cells were identified as AT2-like cluster 1 cells through scRNA barcodes. These clones produce IgA with the progression of pulmonary fibrosis. To determine which cluster of cells the clones came from, we merged the barcodes of the top 3 clonal cell populations with barcodes from single-cell sequencing. Most of these clonal cells were identified as AT2-like cluster 1 cells. Compared with B cells, top 1 clonal cells highly expressed and
。
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The use of the V gene varies among different individuals. As expected, ,
and
were barely expressed in the sections used for spatial transcriptomic sequencing(空间转录组检测BCR基因的表达). We next focused on
, a gene encoding the constant region of the immunoglobulin heavy chain that is crucial for determining the immunoglobulin isotype. As shown, this gene was coexpressed with
. Moreover, the expression of
in the SiO2-56d sample was much higher than that in the SiO2-7d sample, consistent with the expansion of IgA-related clonotypes in the SiO2-56d sample. Therefore, the increased frequency of
use is common in pathological conditions. The IgA-expressing AT2-like cell population might be important in pulmonary fibrosis.
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To verify the presence of IgA-expressing AT2-like cells in fibrotic lung tissue, we used RNAScope, a new technology that can simultaneously detect multiple target RNAs in situ(多技术证明分析的结果). Probes for detecting
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TCR is not amplified in the SiO2-7d or SiO2-56d sample compared with the NS-7d or NS-56d sample, respectively(TCR居然不起作用)
T cells are primarily responsible for cellular immunity, as opposed to humoral immunity(T 细胞主要负责细胞免疫，而不是体液免疫). To evaluate the role of T cell immunity in lung fibrosis, we rebuilt TCR sequences for the NS-7d, SiO2-7d, NS-56d, and SiO2-56d samples from scRNA-seq(单细胞TCR测序分析). There were no notable differences in V(D)J and C gene usage among the four samples. The amino acid sequences of the top 10 complementarity determining regions (CDR3) in the four samples were different, without a specific pattern or shared CDR sequences. The extent of clonal expansion in the four samples showed that more than 80% of the clonotypes of each sample were represented by only one cell, and the clonotype with the greatest expansion represented no more than 3% of all cells. Then, to explore the similarities and differences in clonotypes among the four samples, we analysed the top 30 clonotypes of each sample. Each sample had a unique preferred clonotype, and no clonotype was shared among the four samples（每个样本都有一个独特的首选克隆型，四个样本之间没有共享克隆型）
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然后，我们使用 Loupe（版本 4.1.0，10x Genomics）整合 scRNA 序列和 TCR 的Barcode。 简而言之，携带 TCR 或配对克隆型的细胞在每个样本中被识别为 T 细胞，并且四个样本之间没有显著差异。 总之，这些发现表明样本之间没有显著差异，表明 T 细胞没有参与肺纤维化。
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Immunoglobulin IgA was increased in mouse lung epithelium under TGF-β treatment
GF-β 是一种已知的强纤维化因子，常用于刺激细胞建立体外纤维化模型。 在这里，我们培养了具有AT2特征的小鼠肺上皮细胞系MLE-12，并用TGF-β处理了不同时间。 然后，我们通过蛋白质印迹评估 IgA。 使用抗 IgA 抗体，我们检测到 IgA，一条 75 kDa 的条带，恰好等于 IgA 轻链和重链的总分子量。 细胞用 TGF-β 处理 72 小时后，条带变暗。 为了验证 AT2 细胞可以将 IgA 分泌到 ECM 中，我们将 MLE-12 细胞重新接种到从健康小鼠肺获得的肺 ECM 上，然后用 TGF-β 处理。 蛋白质印迹分析表明，与纯肺 ECM 相比，在 MLE12 细胞和 TGF-β 培养的 ECM 中检测到更多的 IgA。 这种现象表明肺上皮向肺 ECM 分泌 IgA。
Combined analysis of scRNA-seq and spatial transcriptomics showed that more AT2-like cluster 1 cells were accumulated in the SiO2-56d sample
为了进一步研究与纤维化病变相关的肺中cluster 1 细胞的位置，我们使用 Seurat V3.2 基于锚点特征整合我们的数据集，并预测包含在四个部分 (NS) 空间转录点中的主要细胞类型-7d、SiO2-7d、NS-56d、SiO2-56d)(单细胞空间联合分析)。在四个部分中预测了通过单细胞测序鉴定的所有 15 种细胞类型。所有类型的细胞都分散在四组样本中，没有任何明显的模式，这与大脑和肾脏的情况不同，其中特定的细胞cluster与特定的解剖位置相关。正如预期的那样，SiO2-7d 样品中的巨噬细胞比 NS-7d 样品中的巨噬细胞更密集，这与 scRNA-seq 观察到的巨噬细胞数量增加一致。类似地，在 SiO2-56d 样品的病变中发现 AT2 样cluster 1 细胞比在 NS-56d 样品中的密度更高。值得注意的是，SiO2-56d 样品中的 B 细胞没有特殊的分布模式。从空间角度来看，这一结果证实巨噬细胞参与了矽肺，尤其是在早期，BCR+ AT2 样细胞往往在纤维化阶段起重要作用。
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Discussion
通常认为成纤维细胞在肺纤维化中起重要作用。阻断成纤维细胞的药物虽然可以减缓肺纤维化患者肺功能的下降，但不能降低患者的死亡率。因此，在确定肺纤维化的重要事件和分子机制为肺纤维化治疗提供靶点方面还有很多工作要做。我们的研究发现 AT2 样细胞增殖并将 IgA 分泌到肺 ECM 中。这些细胞在细胞总数中所占的比例远远超过其他肺细胞，这些细胞的激活极大地改变了肺 ECM 的组成。 IgA通常分布于消化道和呼吸道的黏膜表面，由B细胞分泌。在我们的肺纤维化模型中，IgA 大量沉积在肺 ECM 中，这是迄今为止世界上首次报道。事实上，肺纤维化疾病在临床上与自身免疫性疾病如结节病和系统性硬化症有关。研究表明，纤维化肺中的 IgA 可以激活成纤维细胞，促进其转分化为肌成纤维细胞并分泌胶原蛋白。我们的发现为 IgA 和成纤维细胞之间的良好接触提供了基础。
肺泡祖细胞可以自我更新、增殖和补充受损的肺泡上皮。 当它们异常增殖时，它们会导致肺泡结构紊乱。 已经报道了三种肺祖细胞。 在我们的研究中，AT2 样细胞cluster 1 更类似于 Sftpc+ Scgb3a1+ 肺祖细胞，它们向 ECM 分泌 IgA。 虽然免疫球蛋白被认为来源于 B 细胞，但研究表明，在肺癌中，上皮细胞也可以分泌免疫球蛋白 IgG。 这是首次发现上皮细胞在非癌症疾病中产生免疫球蛋白.
有人建议特发性肺纤维化将在未来 10 年内重新分类。 考虑到这一点，本研究的发现激励我们研究其他类型的肺纤维化，并根据 IgA 沉积的存在与否对它们进行分类。 靶向消融过度增殖的 AT2 样细胞或阻断 IgA 的产生可能成为治疗肺纤维化的潜在靶点.
Method
Cell type annotation(marker要多搜集一下)
Cell types were determined by clustering and marker gene expression. Cluster
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BCR and TCR sequence reconstruction
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单细胞空间联合的方法就是Seurat的方法。
生活很好，有你更好
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