Two Decades of Publications in Journals Dedicated to Autoimmunity: A Bibliometric Analysis of the Autoimmunity Field from 2004 to 2023

To carry out an in-depth analysis of the scientific research on autoimmunity, we performed the first bibliometric analysis focusing on publications in journals dedicated to autoimmunity (JDTA) indexed by science citation index during the period 2004–2023. Using bibliometric analysis, we quantitatively and qualitatively analyzed the country, institution, author, reference and keywords information of publications in JDTA, so as to understand the quantity, publication pattern and publication characteristics of these publications. The co-occurrence networks, clustering map and timeline map were created by CiteSpace and VOSviewer software to visualize the results. The CiteSpace was also used to analyze the strongest citation burst of keywords, which could describe the frequency, intensity and time period of high-frequency keywords, and indicate the research hotspots in the field. A total of 5 710 publications were analyzed, and their annual distribution number was basically stable from 2004 to 2023, fluctuating around 300. The United States and Italy led the way in terms of the number of publications, followed by France and China. For international cooperation, the developed countries represented by the United States cooperate more closely, but the cooperation was localized, reflecting that there was no unified model of autoimmunity among countries. UDICE-French Research Universities had the greatest number of publications. Subsequently, the number of publications decreased slowly with the ranking, and the gradient was not large. Eric Gershwin and Yehuda Shoenfeld stood out among the authors. They had an excellent academic reputation and great influence in the field of autoimmunity. The results of keyword analysis showed that JDTA publications mainly studied a variety of autoimmune diseases, especially SLE and RA. At the same time, JDTA publications also paid special attention to the research of cell function, autoantibody expression, animal experiments, disease activity, pathogenesis and treatment. This study is the first to analyze the publications in JDTA from multiple indicators by bibliometrics, thus providing new insights into the research hotspots and development trends in the field of autoimmunity.


Introduction
With the passage of time and the continuous development of disciplines, there has been a considerable increase in scientific publications (including in the field of autoimmunity).When researchers look up publications in a certain field, a large number of literature are available to read and study.However, they are also faced with many problems.First, the existing literature has a wide range of topics, different research types, different research depths, and uneven quality.Secondly, the publication patterns of different journals are flourishing, and the types and requirements of publications are also different, especially the publications on autoimmunity topics (POAT).POAT has been published in a variety of journal types, including journals dedicated to autoimmunity (JDTA), immunology subspecialty journals, and general medical journals.Among them, there are three main JDTA indexed by science citation index (SCI), including Autoimmunity Reviews [1], Journal of Autoimmunity [2] and Autoimmunity [3].
These three journals cover all types and different levels of articles in the field of autoimmunity due to their large impact factor span (from 3.5 to 13.6) and comprehensive article types, which is of great significance for guiding the research in the field of autoimmunity.A large number of high-quality autoimmunity-related articles (ARAs) were published in these three journals, which closely follow the research hotspots and are in the forefront of the field, and have a good guiding role for researchers who want to carry out some deep and innovative research [4][5][6][7][8].At the same time, they also published some basic ARAs, which is very helpful for novice researchers to quickly and systematically understand and learn professional knowledge in this field [9][10][11].Therefore, analyzing the characteristics of the articles published in these three journals will help researchers better understand the basis, frontier, hot spots and challenges in the field of autoimmunity and is also helpful for readers to quickly obtain an overview of the development data of these journals, such as content, subject, and influencing factors.
Bibliometric analysis is a kind of literature analysis method that can quantitatively and qualitatively analyze the quantity, publication pattern and publication characteristics of published literature in a particular field [12].It can analyze the author, keywords, periodicals, state, institution references and other information of publications, using visualization tools, including CiteSpace, VOSviewer, and HistCite tools, so as to provide clues and theoretical basis for studying the research trends and focus of various disciplines [13][14][15].
Therefore, the objective of this study was to analyze the characteristics of articles published in these three main JDTAs using bibliometric methods, which will help researchers to better understand the fundamentals, frontiers, hotspots and challenges in the field of autoimmunity.

Journal Selection
Web of Science (WOS), one of the world's most trusted publishers of global citation databases, is a leading platform for scientific research [16].The JDTAs were identified by searching the WOS Core Collection (WOSCC) database using "autoimmunity" as the search term in the "Publication/Source Title" field.Finally, three leading journals were selected, including "Autoimmunity Reviews" [1], "Journal of Autoimmunity" [2] and "Autoimmunity" [3].
"Autoimmunity Reviews" usually publishes cutting-edge structured reviews authored by leading experts in the field, covering various topics in autoimmunity.The articles will encompass all areas of autoimmune research, with a focus on bridging the gap between basic and clinical sciences.
The "Journal of Autoimmunity" publishes papers relating to all aspects of autoimmunity, including mechanisms of self-recognition, regulation of autoimmune responses, experimental autoimmune diseases, diagnostic autoantibody testing, epidemiology, pathophysiology, and therapy.It particularly emphasizes but is not limited to papers involving genetics, molecular biology, and cell biology in the discipline.
"Autoimmunity" is an internationally peer-reviewed journal that publishes articles on cellular and molecular immunology, immunogenetics, and molecular biology related to immunity and autoimmunity.The journal focuses on immune system cells, with a particular interest in the regulatory mechanisms of T cells and B cell antibody responses, emphasizing the intrinsic epigenetic and metabolic processes within immune cells.

Data Processing
Literature published in these three JDTAs was searched in WOSCC, and the detailed query formulation was described as follows: SO = ("JOURNAL OF AUTOIMMUNITY" OR "AUTOIMMUNITY REVIEWS" OR "AUTOIMMUN-ITY").Because WOSCC only covers the literature published in these three JDTAs since 2004, the literature we analyzed was from January 1, 2004 to June 21, 2023.The document types were limited to reviews (systematic or otherwise) and original articles (any design).Meeting, letter, case report, editorial material, abstract, retractions were excluded.The bibliometrics description of all documents, including types of documents, most prolific articles, authors, institutions, countries and so on was collected.A hierarchical filtering process was used to ensure all study types that were mutually exclusive and that each article was only indexed for 1 study type.We reviewed a random 100 sample of the records to ensure classification accuracy for specialty and study type.After removing the duplicates manually, a total of 5,710 publications, including 3,560 articles and 2,150 reviews, were selected as the final data set for further bibliometric analysis.The search and analysis processes are shown in Fig. 1.In our study, ethical review was not required.

Statistical Analysis
The bibliometrics description of all documents was analyzed using the Microsoft Office Excel 2022, CiteSpace (v.6.2.R4 Advanced) [17] and VOSviewer (v.1.6.19)[18].The histogram produced by Microsoft Office Excel showed the different number publications by different years, countries, institutions and authors.CiteSpace and VOSviewer were used to create co-occurrence networks, in which the size and color of the circles represent the number and year of publications, respectively, and the number and thickness of the lines between the circles represent the frequency and intensity of cooperation between the research objects, respectively [19].The clustering map and timeline map were drawn by CiteSpace according to the logarithmic likelihood ratio of keywords and were used to describe the research direction and the change progress of research hotspots over time.When the clustering modular value Q (Modularity Q) > 0.3, the clustering contour index S (Mean Sihouette) > 0.5 indicates a reasonable clustering, with clear structure and high reliability.The clustering map and timeline map in this study all met the requirements.The CiteSpace software was used to analyze the strongest citation burst of keywords, which could describe the frequency, intensity and time period of high-frequency keywords, and indicate the research hotspots in the field [20,21].

Publication Numbers Sorted by Year
A total of 5,710 articles were analyzed, of which 3,560 (62.35%) were original articles and 2,150 (37.65%) were reviews.From 2004 to 2010, the number of literature increased slowly and steadily, up to 329 papers, suggesting that more and more attention had been paid to the field of autoimmunity.From 2011 to 2017, the number of publications showed a slight fluctuation, with the annual number of publications ranging from 275 to 341.Since 2017, the annual number of publications stabled at about 300 (Fig. 2).

Country Co-occurrence Network
As shown in Fig. 3, among the 96 countries that have published papers in JDTA, the United States had the highest number of publications.The United States led the way with 1,697 (19.87%) publications, followed by Italy with 1,063 (12.44%),France with 581 (6.80%),China with 580 (6.80%), Germany with 476 (5.58%) and England with 424 (5.00%), and the remaining countries/regions had published less than 5.00% articles.In addition, France and Sweden played a "bridging" role in the country cooperation.

Country Timeline Map
The results of country timeline map showed that the United States [22], Italy [23] and China [5] mainly focused on autoimmunity, and the attention had continued to be popular since 2004 till now.Norway [24], Poland [25] and Hungary [26] mainly studied SLE, and the focus was mainly from 2018 to 2021.France [27], Sweden [28], and Mexico paid more attention to B cell activating factor (BAFF), among which France paid more attention, and the time span was longer, from 2004 to now, especially from 2014 to 2021.Meanwhile, India, Japan and Canada were interested in reactive oxygen species, but the number of their publications decreased in the past two years (Fig. 3).

Institution Co-occurrence Network
The Citespace software integrates various aspects of information from literature, including co-occurrence patterns, citation relationships, keywords, and topics, to automatically cluster institutions.Using Citespace's automatic clustering, 574 publishing institutions were identified and categorized into 10 groups (Fig. 4).Among these institutions, UDICE-French Research Universities, University of California System and Institut National de la Sante et de la Recherche Medicale (Inserm) ranked the top three in terms of publication numbers, belonging to France, the United States and France and with 385, 335 and 329 publications, respectively.Among the top 20 institutions in the number of publications, 8 were affiliated to France, 4 to the United States, 3 to Israel, 2 to Italy, 2 to Spain and 1 to the United Kingdom, which may be one of the reasons why the United States, Italy, and France lead in the number of publications (Fig. 4).However, China and Germany, which also ranked in the top 5% of the number of publications, had no institutions in the top 20, might be because the number of publications by each institution is relatively scattered and average.

Author Co-occurrence Network
The number of scholarly publications of an author can represent the research activities and contributions in the field to some extent.The top three authors in the number of publications were Eric Gershwin, Yehuda Shoenfeld and Andrea Doria, who were affiliated with the University of California, Tel Aviv University and University of Padua, that were institutions ranking first, 8th and 18th in terms of the number of publications, respectively (Fig. 5).Eric Gershwin had published 174 papers, accounting for 51.94% of the total number of publications by the University of California System.Yehuda Shoenfeld, the author with the second largest number of publications, came from Israel, with 172 publications, accounting for 43.00% of the total number of publications in Israel.The author Andrea Doria, who ranked third in the number of publications, came from the University of Padua in Italy, with 73 publications, accounting for 57.94% of the total number of publications of the University of Padua.Among the top 10 authors in the number of publications, 5 authors were all from Italy, contributing to Italy ranking second in the number of publications.

Author Clustering Map
Author clustering results (Fig. 5) showed that many authors paid more attention to the topic of "ANCA-associated vasculitis," among which Luc Mouthon [32] and Patrice Cacoub [33] had a large number of publications.Eric Gershwin [34] with the first number of publications and Juan-Manuel Anaya [35] with the seventh number of publications focused on "primary biliary cirrhosis," and they had close cooperation.Shoenfeld Yehuda [36] and Pierre Youinou [37] were interested in the functional study of "B lymphocyte" and published many articles, ranking second and eighth, respectively.Andrea Doria [38] and Ricard Cervera [39], as the third and fourth authors in the number of publications, paid more attention to "lupus nephritis."

Co-cited Author Analysis
Co-author analysis is a powerful method to describe the association between the authors, institutions and countries in a particular research field or a journal.The results of cocited author analysis showed that the top five cited authors were Yehuda Shoenfeld, Ricard Cervera, Carlo Selmi, Shimon Sakaguchi and Michelle Petri, with cumulative citations reaching 520, 361, 319, 310 and 308 times, respectively (Fig. 5).Professor Yehuda Shoenfeld was the founder of the Zabludowicz Center for Autoimmune Diseases at the Sheba Medical Center.His clinical and scientific works focused on autoimmune and rheumatic diseases.He had published more than 1960 papers in many top journals, and these publications had been cited more than 55,000 times, some of which had become cornerstones in science and clinical practice.Professor Ricard Cervera, from Barcelona, was a key member of several Barcelona institutes for autoimmune diseases.His current major research interest included clinical and epidemiological aspects of systemic autoimmune diseases, particularly SLE and the antiphospholipid syndrome.Dr. Cervera had published more than 800 scientific papers, which had a great guiding role in the field of SLE research.Professor Carlo Selmi was leading the Rheumatology and Clinical Immunology Unit at Humanitas Research Hospital.Since 2009, he was the responsible of the Autoimmunity and Metabolic Laboratory, dedicated to the study of the possible mechanism linked to the progression of autoimmune diseases and chronic inflammatory diseases, including the clinical epidemiology and pathogenetic mechanisms of autoimmune liver disease, connective tissue disease (particularly systemic sclerosis), and psoriatic arthritis.He had coauthored over 400 publications with a D-index of 84 and citations nearly 20,000 times.

Citation Analysis
The Highly Cited Publications There were 33 highly cited papers in JDTA, including 26 reviews and 7 articles (Table 1).Of these papers, 22 were from Autoimmunity Reviews and 11 were from Journal of Autoimmunity.There were 16 articles related to COVID-19 (ranked 1, 2, 6, 9, 10, 15,17,18,20,23,25,26,27,28,30,31, respectively): 1 and 15 described the COVID-19 pandemic in detail, including the clinical manifestations, epidemiological characteristics, pathogenesis, control strategies; 2, 9, 10 explored the role of cytokines, especially interleukin-6, in the occurrence and development of COVID-19; 6, 17 investigated the possible therapeutic effects of tocilizumab and convalescent plasma on COVID-19, respectively; 18, 20, 23, 31 were reviews of the association between COVID-19 and autoimmunity, especially RA; 25, 26 described the characteristics of SARS-CoV-2 and its variants and their effects on the original antibodies; 27 was a meta-analysis and a review focusing on the protective effect of SARS-CoV-2 vaccines in patients with immune-mediated inflammatory diseases; 28 discussed the utility, importance, development prospects and vaccination strategies of SARS-CoV-2 vaccines; 30 comprehensively described the Post-COVID-19 syndrome, especially changes in autonomic nervous system function, and introduced some possible treatment measures.The above literatures have comprehensively studied and analyzed the etiology, symptoms, diagnosis, treatment, vaccine, complications, prognosis and other aspects of COVID-19.

The Top 20 Cited References
As shown in Table 2, the top 20 cited references could be divided into 6 categories: First, the reference ranked 1 formed unified, standardized and specific definitions of common vasculitis; Second, ranked 2, 5, 8, 16 references discussed the role of cell damage, epigenetics, protective T cell responses, regulatory T cells involved in the mechanisms of autoimmune diseases; Third, the references ranked 3, 12, 15, 18, 19 were the research of some specific autoimmune diseases, including SLE, systemic sclerosis, thyroid autoimmunity, primary biliary cirrhosis and SS; Fourth, the references ranked 4, 7, 13, 14 introduced the achievements of four outstanding immunologists, Susumu Ikehara; Ian Reay Mackay, Noel Rose, and Haralampos M. Moutsopoulo; Fifth, the references ranked 6, 10, 11 described the geoepidemiology and its association with autoimmunity; Sixth, the references ranked 9, 17, 20 explored the relationship between gender, environment, pregnancy and autoimmunity, respectively.Finally, there were 303 keywords that appeared more than 10 times, among which the co-occurrence network of the top 25 keywords was shown in Fig. 6.In this mapping, the size of the node was proportional to the number of occurrences of the keyword.According to the corresponding year of occurrence of these keywords, different colors mark different years.It can be seen that "systemic lupus erythematosus," "t cells, rheumatoid arthritis," "antibody," "expression," "cells," "autoimmune," "disease," "autoantibody" and "multiple sclerosis" received the most attention, with the number of publications of 1,234, 1,162, 1,014, 919, 841, 820, 743, 618, 535, 426, respectively (Fig. 6).

Keywords Clustering Map and Timeline Map
As shown in Fig. 6, the keywords were clustered into 11 categories, namely #0 antiphospholipid syndrome, including antibody, autoantibody, SS, systemic sclerosis, classification and so on; #1 dendritic cells, including t cells, expression, cells, autoimmune, disease, b cells, and so on; #2 RA, including RA, peripheral blood, genome wide association and so on; #3 rituximab, including therapy, double blind and so on; #4 SLE, including SLE, disease activity and so on; #5 type 1 diabetes; #6 graves disease, including graves disease, association and so on; #7 myasthenia gravis, #8 autoimmune hepatitis, #9 multiple sclerosis, including multiple sclerosis, central nervous system and so on; and #10 zika virus.

Keywords with Strongest Citation Bursts
Burst analysis was used to capture keywords with a sharp increase in popularity during a certain period of time.Figure 7 showed the top 25 keywords with the strongest burst.As shown in Fig. 7, the keyword with the strongest burst was "genome wide association (GWAS)", with a strength of 14.13, and the burst lasted from 2013 to 2018.This might be due to that with the use of GWAS methods in various research fields, related publications of GWAS in the field of autoimmune diseases also sprung up.Meanwhile, the burst strength of "systematic review" and "mellitus" was 13.39 and 13.38, ranking second and third, respectively.The burst of "systematic review" occurred from 2017 to now, suggesting that systematic review, as the most systematic and rapid means to understand a certain research field, was still concerned and recognized by researchers.However, the burst time of "mellitus" was earlier, between 2004 and 2008, when attention to diabetes, especially type 1 diabetes mellitus, increased dramatically.

Discussion
This bibliometric analysis study provides a first comprehensive overview of publications in JDTAs, including three journals, Autoimmunity Review Journal of Autoimmunity and Autoimmunity, over the last two decades, from 2004 to 2023.Since 2004, the annual number of JDTA publications had been basically stable, fluctuating around 300, suggesting that the development of these three journals was stable and mature, and they strictly control the quantity and quality of publications.
Globally, the United States and Italy led the way in terms of the number of publications, followed by France and China.According to the results of national analysis, United States and Italy began to research in the related field and published a large number of publications since 2004, especially the United States, of which publications from 2004 to 2013 accounted for a large proportion of its all publications.France began to have a large number of publications in 2015, focusing on 2015-2019.At the same time, China began to publish a large number of studies in 2017, and the number of publications has also maintained at a high level since then.In addition, the results of country clustering based on keywords showed that the France and United States had a good cooperative relationship with other countries.For international cooperation, the developed countries represented by the United States cooperate more closely, but the cooperation was localized, reflecting that there was no unified model of autoimmunity among countries.Therefore, we believe that cooperation between countries in the same research field is very likely to promote each other's research progress, while cooperation between countries with different focuses can effectively fill research gaps in their respective fields.
In terms of research institutions, UDICE-French Research Universities published the most articles, and subsequently, the number of publications decreased slowly with the ranking, with no large gradient.There was extensive cooperation among research institutions, especially several French institutions in the top 20, which were closely connected and cooperated well.However, the cooperation among other institutions was weak and still needed to be strengthened.None of top 20 institutions were from China and Germany, which ranked fourth and fifth in the number of publications, respectively, which may be due to the relatively dispersed and average number of publications by institutions in these two countries.Hence, for institutions in China and Germany, strengthening cooperation between them, focusing on and assisting leading research institutions, helps enhance the influence of respective institutions, accelerates the research process, improves research quality, and facilitates wider   Eric Gershwin and Yehuda Shoenfeld stood out among the many authors because of their excellent academic reputation and dominance in the field of autoimmunity.Eric Gershwin mainly focused on immunology, primary biliary cirrhosis and autoimmunity.The concepts of his autoimmunity study were interwoven with issues in autoimmune disease, molecular mimicry, immune tolerance and genetic predisposition.Eric Gershwin worked closely with authors Carlo Selmi and Juan-Manuel Anaya, who ranked 6th and 7th in the number of publications, respectively.They had collaborated on several publications focusing on autoimmune diseases, especially primary biliary cirrhosis.Yehuda Shoenfeld, as the most cited author of JDTA, also has a great influence in the field.Yehuda Shoenfeld worked mostly in the field of autoantibody, limiting it down to topics relating to adjuvant and, in certain cases, autoimmune/inflammatory syndrome induced by adjuvants.His research integrated issues of SLE and Anti-SSA/Ro autoantibodies in his study of autoantibody.However, the author analysis also suggested that the density of links between authors was not enough and still needed to be strengthened.In terms of authors, notable research achievements in the field of primary biliary cholangitis have been made by scholars Eric Gershwin, Carlo Selmi, Juan-Manuel Anaya et al.Collaborations among these esteemed authors have the potential to greatly drive research advancements in primary biliary cholangitis.
Collaborative efforts among these esteemed authors hold immense promise for propelling research progress in primary biliary cholangitis.
The results of keyword analysis showed that JDTA publications mainly studied a variety of autoimmune diseases, especially SLE and RA.At the same time, JDTA publications Fig. 7 The top 25 keywords with the strongest citation bursts Page 14 of 16 also paid special attention to the research of cell function, autoantibody expression, animal experiments, disease activity, pathogenesis and treatment.Based on the information from emerging keywords, we cannot only gain insights into past hotspots in research fields but also can preliminarily predict future keywords that might become popular.Firstly, terms related to health and biomedical fields, such as "gut microbiota" and "immune system," due to their recent high citation intensity, may continue to be popular.Additionally, with the development of technology and research, new research directions and fields may emerge, bringing forth new popular keywords.For example, in fields like genomics, precision medicine, and the integration of artificial intelligence with medicine, new attention-grabbing keywords may arise.This feature of Citespace reminds us that it is not just a tool for bibliometrics; with the development of the big data era, AI technology also holds significant importance in analyzing research hotspots and predicting trends, deserving further exploration and consideration.
Some limitations still exist in our studies.Firstly, although the WOSCC database had the most complete coverage of articles, some papers from different databases cannot be retrieved.Secondly, given our study focus on bibliometric analysis of JDTA, and the number of eligible journals is relatively limited; we opted not to compare these three target journals separately to ensure a comprehensive overview of the field.Thirdly, we only analyzed articles and reviews and excluded meeting, letter, case report, editorial material, abstract, retractions.These may lead to incomplete data collection and different results.

Conclusion
This bibliometric analysis study provides a comprehensive overview of JDTA over the last two decades.The number of JDTA publications was basically stable, fluctuating around 300 yearly.Globally, the United States and Italy were in the leading positions in terms of the number of publications.Among the Research institutions, UDICE-French Research Universities had the greatest impact on publications.Eric Gershwin and Yehuda Shoenfeld contributed greatly to the publications of POAT.Different countries, institutions and authors needed to strengthen cooperation and communication.The publications of JDTA mainly studied a variety of autoimmune diseases, especially SLE and RA.JDTA focused on cell function, autoantibody expression, animal experiments, and disease mechanisms.They represented the current research and the development trend of future researches in the field of autoimmunity.

Fig. 3
Fig. 3 Analysis of the country distribution of publications.Note A: the co-occurrence network of countries; B: top 20 countries by number of publications and their centrality; C: the timeline map of countries

Fig. 6
Fig. 6 Analysis of the keyword distribution of publications.Note A: the co-occurrence network of keywords; B: top 20 keywords by number of publications; C: the clustering map of keywords; D: the timeline map of keywords

Table 1
The highly cited papers