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Xueyan Shan,1,2 Yongpeng Ge3 1Department of Rheumatology, Guang’anmen Hospital, China Academy of Chinese Medical Sciences, Beijing, People’s Republic of China; 2Postgraduate School, Beijing University of Chinese Medicine, Beijing, People’s Republic of China; 3Department of Rheumatology, The Key Laboratory of Myositis, China-Japan Friendship Hospital, Beijing, People’s Republic of ChinaCorrespondence: Yongpeng Ge, Department of Rheumatology, The Key Laboratory of Myositis, China-Japan Friendship Hospital, Yinghua East Road, Chaoyang District, Beijing, 100029, People’s Republic of China, Email gyp2016@163.comObjective: To investigate the clinical features, severity and prognosis of interstitial lung disease (ILD) in patients with mixed connective tissue disease (MCTD).Methods: We performed a retrospective study on clinical data of MCTD patients admitted to China-Japan Friendship Hospital between October 2012 and October 2022. Data including long-term follow-up were retrieved from medical records. We compared MCTD patients with and without ILD in terms of clinical features, laboratory and imaging findings, severity and treatment response.Results: A total of 59 patients were included, with a mean age of 46 years, among which 91.5% (n = 54) were females. Symptoms of pulmonary involvement were present in 44 patients (74.6%, 95% CI: 62.3– 84.9%). Based on lung high-resolution computed tomography (HRCT), ILD was diagnosed in 39 (66.1%) patients, among which 31 (79.5%) showed nonspecific interstitial pneumonia (NSIP) as the radiological pattern, 21 (53.9%) showed a reticulation pattern, while 24 (61.5%) showed ground glass opacity (GGO). Eight (13.6%) patients had pulmonary arterial hypertension (PAH), and 7 (11.9%) had pleural effusions. Based on pulmonary function tests (PFTs), 27 patients were divided into the mild 13 (48.1%) and moderate 14 (51.9%) groups. Multivariate analysis showed that gastroesophageal reflux (GER; OR=5.28, p=0.010) and cough (OR=4.61, p=

The major histocompatibility complex (MHC) is a dynamic genome region with an essential role in the adaptive immunity of vertebrates, especially antigen presentation. The MHC is generally divided into (classes I, II and III) containing genes of similar function across species, but with different gene number and organisation. Crocodylia (crocodilians) are widely distributed and represent an evolutionary distinct group among higher vertebrates, but the genomic organisation of MHC within this lineage has been largely unexplored. Here, we studied the MHC region of the saltwater crocodile (Crocodylus porosus) and compared it with that of other taxa. We characterised genomic clusters encompassing MHC class I and class II genes in the saltwater crocodile based on sequencing of bacterial artificial chromosomes. Six gene clusters spanning ∼452 kb were identified to contain nine MHC class I genes, six MHC class II genes, three TAP genes, and a TRIM gene. These MHC class I and class II genes were in separate scaffold regions and were greater in length (2-6 times longer) than their counterparts in well-studied fowl B loci, suggesting that the compaction of avian MHC occurred after the crocodilian-avian split. Comparative analyses between the saltwater crocodile MHC and that from the alligator and gharial showed large syntenic areas (>80% identity) with similar gene order. Comparisons with other vertebrates showed that the saltwater crocodile had MHC class I genes located along with TAP, consistent with birds studied. Linkage between MHC class I and TRIM39 observed in the saltwater crocodile resembled MHC in eutherians compared, but absent in avian MHC, suggesting that the saltwater crocodile MHC appears to have gene organisation intermediate between these two lineages. These observations suggest that the structure of the saltwater crocodile MHC, and other crocodilians, can help determine the MHC that was present in the ancestors of archosaurs.