The purpose of this study is to elucidate the impact of bleomycin on the degree of lung injury and development of mediastinal fat-associated lymphoid clusters (MFALCs) in the lymphoproliferative mouse model (MRL/MpJ-Faslpr/lpr “Lpr”) and its control strain (MRL/MpJ “MpJ”). We analyzed immune cells, the degree of proliferation, lymphatic vessels (LVs), and high endothelial venules (HEVs) in lungs and MFALCs in Lpr and MpJ mice on the 7th and 21st days following intranasal instillation of either bleomycin (BLM group) or PBS (PBS group). The BLM group showed a significant increase in the size of MFALCs, lung injury score, and positive area ratios of LVs, HEVs, and immune cells (especially macrophages, B- and T-lymphocytes) on both days 7 and 21. Interestingly, the lungs in the BLM group on day 21 showed higher collagen deposition and cellular infiltration in MpJ and Lpr, respectively. Moreover, significant positive correlations were observed between the size of MFALCs and lung injury. In conclusion, BLM could exert lung fibrosis or lymphoproliferative infiltration in chronic stages in MpJ and Lpr, respectively, and this varied effect could be due to the variations in the degree of immune cell proliferation and the development of LVs and HEVs among the studied strains.

Diabetes is a devastating global health problem and is considered a predisposing factor for lung injury progression. Furthermore, previous reports of the authors revealed the role of mediastinal fat-associated lymphoid clusters (MFALCs) in advancing respiratory diseases. However, no reports concerning the role of MFALCs on the development of lung injury in diabetes have been published. Therefore, this study aimed to examine the correlations between diabetes and the development of MFALCs and the progression of lung injury in a streptozotocin-induced diabetic mouse model. Furthermore, immunohistochemical analysis for immune cells (CD3+ T-lymphocytes, B220+ B-lymphocytes, Iba1+ macrophages, and Gr1+ granulocytes), vessels markers (CD31+ endothelial cells and LYVE-1+ lymphatic vessels “LVs”), and inflammatory markers (TNF-α and IL-5) was performed. In comparison to the control group, the diabetic group showed lung injury development with a significant increase in MFALC size, immune cells, LVs, and inflammatory marker, and a considerable decrease of CD31+ endothelial cells in both lung and MFALCs was observed. Furthermore, the blood glucose level showed significant positive correlations with MFALCs size, lung injury, immune cells, inflammatory markers, and LYVE-1+ LVs in lungs and MFALCs. Thus, we suggest that the development of MFALCs and LVs could contribute to lung injury progression in diabetic conditions.