Background The immune system is one of the most complex regulatory systems in the body and is essential for the maintenance of homeostasis. Despite recent breakthroughs in immunology, the regulation of the immune system and the etiology of autoimmune diseases such as lupus remain unclear. Systemic lupus erythematosus is a systemic autoimmune disease with abnormally and inconsistently expressed pro-inflammatory cytokines. Pyroptosis is a pro-inflammatory form of programmed cell death that is associated with systemic lupus erythematosus. The thymus and spleen are important immune organs involved in systemic lupus erythematosus. Therefore, this study investigated the difference in expression of pyroptosis-inducing pro-inflammatory cytokines between the spleen and thymus in lupus model mice and in control mice, to describe immune regulation at the organ level. Objective To investigate differences in the expression of pyroptosis-inducing cytokines in the spleen and thymus and to explore immune regulatory networks at the organ level. Methods Two groups of lupus mice and two groups of control mice were utilized for this study. Using the thymus and spleen of experimental animals, mRNA expression levels of five pyroptosis-inducing cytokines (interleukin 1β, interleukin 18, NLRP3, caspase-1 and TNF-α) were determined via quantitative polymerase chain reaction. In addition, tissue distribution of these cytokines was investigated via immunohistochemistry. Results All five pyroptosis-inducing inflammatory cytokines showed higher expression in the spleen than in the thymus ( p < 0.05). Moreover, the spleen/thymus expression ratios of all five pyroptosis-inducing cytokines were not statistically different between the four experimental groups. Expression of all five cytokines exhibited a stable ratio (spleen/thymus ratios). This distinctive stable spleen/thymus ratio was consistent in all four experimental groups. The stable spleen/thymus ratios of the five inflammatory cytokines were as follows: interleukin 1β (2.02 ± 0.9), interleukin 18 (2.07 ± 1.06), caspase-1 (1.93 ± 0.66), NLRP3 (3.14 ± 1.61) and TNF-α (3.16 ± 1.36). Immunohistochemical analysis showed the cytokines were mainly expressed in the red pulp region of the spleen and the medullary region of the thymus, where immune-activated cells aggregated. Conclusion The stable spleen/thymus expression ratios of pyroptosis-inducing cytokines indicated that immune organs exhibit strictly regulated functions to maintain immune homeostasis and adapt to the environment.

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Objective The objective of this study was to observe the expression features of erythroblast macrophage protein (EMP) between the tissues of MRL/lpr mice, a mouse model of systemic lupus erythematosus (SLE), and control mice. Methods We examined the serum ANA in both mice groups through indirect immunofluorescence (IIF). Expression features of EMP in bone marrow, liver, renal, spleen, brain, and lung tissues of the MRL/lpr mice and control mice groups were followed using quantitative real-time polymerase chain reaction (Q-PCR). Meanwhile, the expression of EMP was located through immunohistochemical (IHC) studies and the expressive cell identified through double immunofluorescent labeling. Results IIF showed that lupus mice have strong positive fluorescence, but no significant fluorescence was observed in control mice. Q-PCR detection revealed that EMP was expressed in the marrow, liver, renal, spleen, lung, and brain tissues of lupus mice. The highest levels were observed in the bone marrow, but there was no statistical difference between these tissues. EMP mRNA expression in the liver ( t = 2.747, p = 0.01) and bone marrow ( t = 3.853, p = 0.008) of lupus mice was significantly higher than in the control mice. However, no differences in EMP mRNA expression were observed in the renal, spleen, lung, and brain tissues between the lupus and control mice ( p > 0.05). In addition, the IHC results showed that EMP protein is ubiquitously expressed in all of the tissues of the lupus and control mice. The positive expression rate in the bone marrow and liver tissues of the lupus mice was higher than in the control mice, but without an obvious difference in the other tissues. The double IF staining method shows that EMP protein was expressed in macrophages in the tissues of the lupus mice and the control mice. Conclusions Our data showed that EMP is ubiquitously expressed in macrophages at all of the tissues of the lupus and control mice. However, the expression of EMP in bone marrow and liver tissues of lupus mice was higher than in the control mice, which indicates that EMP may be important in the development of SLE.