Modulation of immune responses and suppression of experimental autoimmune myasthenia gravis by surgical denervation of the spleen

Suppression of the CD28/B7 pathway reduces the occurrence and development of myasthenia gravis and cytokine levels

BACKGROUND

Myasthenia gravis (MG) is an antibody-mediated, autoimmune neuromuscular disease. Reports have indicated that the CD28/B7 ligand interactions play a crucial role during primary immune responses. Hence, the aim of the present study was to investigate the possible effects of the CD28/B7 pathway on the occurrence and development of MG and its associated cytokine factors.

METHODS

An experimental autoimmune myasthenia gravis (EAMG) was initially established by immunization of Lewis rats with acetylcholine receptor (AChR) α97-116 peptide. Then the rats were treated with dexamethasone and CTLA4-Ig (used for inhibiting the CD28/B7 pathway). Serum levels of AChR IgG and AChR IgG2b were then detected using ELISA. The clinical features, muscle contraction function, AChR content, expression of CD28, CTLA4, B7.1 and B7.2 in mononuclear cells of peripheral blood and the secretion of cytokines (INF-γ, IL-2, IL-10 and IL-12) in serum of rats were measured. Finally, lymphocyte proliferation upon CTLA4 IgG treatment was examined in vitro.

RESULTS

Inhibition of the CD28/B7 pathway and dexamethasone were found to significantly improve clinical symptoms of EAMG rats, reduce serum levels of AChR IgG, AChR IgG2b, INF-γ, IL-2, IL-10 and IL-12, the expression of CD28, CTLA4, B7.1 and B7.2 in mononuclear cells of peripheral blood, and enhance muscle contraction function and AChR content in the muscle in vivo. Meanwhile, CTLA4 IgG could abolish the increased lymphocyte proliferation following AChR stimulation in vitro.

CONCLUSION

Overall, the suppression of the CD28/B7 pathway by CTLA4-Ig can have the potential to retard the occurrence and development of MG.

Protective effect of Sijunzi decoction on neuromuscular junction ultrastructure in autoimmune myasthenia gravis rats

OBJECTIVE

To investigate the protective role of Sijunzi decoction in neuromuscular junction (NMJ) and muscle cell mitochondria ultrastructure; as well as its effects on the amount of adenosine triphosphate (ATP) and the activities of mitochondrial respiratory chain complexes I, II, III, and IV in autoimmune myasthenia gravis rats.

METHODS

An experimental autoimmune myasthenia gravis (EAMG) rat model was established by inoculating rats with acetylcholine receptors extracted from Torpedo. Rats were divided into three groups: model, prednisone, and Sijunzi decoction, and were fed physiological saline, prednisone, or Sijunzi decoction, respectively. NMJ and muscle cell mitochondria ultrastructure were observed by transmission electron microscope. The amount of ATP was assessed by high performance liquid chromatography. The activities of mitochondrial respiratory chain complexes I, II, III, and IV was determined using the Clark oxygen electrode method.

RESULTS

In the model group, there were sparse muscle fibers, with decreased mitochondria, and sparse, diffluent, or absent NMJ folds. After intervention with Sijunzi decoction, the above pathology changes were improved: muscle fiber structure was clear and complete; the mitochondria count was higher; and the NMJ structure was close to normal. Gastrocnemius muscle mitochondria in the model group produced significantly less ATP than those in the prednisone group (P < 0.01). Conversely, the ATP of Sijunzi decoction group was significantly higher than prednisone group (P < 0.01). The activities of gastrocnemius muscle mitochondrial respiratory chain complexes I, II, III, and IV in both the prednisone and Sijunzi decoction groups was dramatically higher compared with the model group (P < 0.05). The activities of complexes I and III in the Sijunzi decoction group were significantly higher than those in the prednisone group (P < 0.05), but there was no obvious difference in complex II or IV activities between the two groups (P > 0.05).

CONCLUSION

Sijunzi decoction improved pathological changes in muscle mitochondria and NMJ, enhanced the amount of ATP in gastrocnemius muscle mitochondria, and improved the activities of respiratory chain complexes I, II, III, and IV (especially I and III) of the EAMG rats.

A novel nervous system-induced factor inducing immune responses in the spleen

This study relates to a novel mediator signaling between the nervous system and the spleen following an immune challenge. Using enzyme-linked immunospot and cell proliferation assays, we found that supernatants of cultured splenocytes prepared from subcutaneously trypanosome-inoculated rats and mice spleens obtained immediately after inoculation and added to naive cells significantly stimulate interferon-gamma production and cell proliferation compared to phosphate-buffered saline-inoculated animals. This action was abrogated by surgical denervation of the spleen. Using the fluorescent differential display technology, the gene involved in this process was identified and further cloned and its sequence was mapped to chromosome 14 (GenBank accession number: EU552928). Protein expression revealed approximately 15 kDa molecule with biological activities similar to the cultured supernatants of splenocytes obtained directly from parasite-inoculated animals. Antibodies raised against the protein blocked the activities of both the protein and the supernatant and also recognized a band in the active supernatant with the same molecular mass as the protein. Furthermore, the protein was able to reactivate experimentally immunosuppressed cells by regaining their ability to proliferate, suggesting that such a nervous system-induced immune system-released activating agent (ISRAA) may have a potential therapeutic benefit in immunocompromised situations and in further understanding the mechanism for innate immunity commencement and action.

Perspective is everything: an irreverent discussion of CNS-immune system interactions as viewed from different scientific traditions

The immune system is a host defense system comprised of both innate mechanisms able to rapidly recognize and respond to conserved pathogen associated molecular patterns (PAMPs) as well as adaptive mechanisms able to respond to a wide variety of non-conserved and conserved pathogen associated molecules. In vitro and in vivo studies have demonstrated that the kinetics and type of immune response triggered by pathogenic insults is a function of both the nature of the insult and the subsequent cross-regulatory interactions between the responding immune cells. In this context, the potential immunomodulatory influences of the nervous system have been often viewed as exerting minimal modulatory effects and thus of being largely irrelevant in the development of immune responses. Here, using a Saturday Night Live (SNL)-styled point:counterpoint format, we discuss whether and to what extent the nervous system can shape the responses of the immune system. Finally, we examine whether primary degenerative disorders of the CNS are likely to lead to alterations in immune function.