Basic science for the clinician 30: The immunologic synapse

Neuroimmune Interaction in the Regulation of Peripheral Opioid-Mediated Analgesia in Inflammation

Peripheral immune cell-mediated analgesia in inflammation is an important endogenous mechanism of pain control. Opioid receptors localized on peripheral sensory nerve terminals are activated by endogenous opioid peptides released from immune cells to produce significant analgesia. Following transendothelial migration of opioid-containing leukocytes into peripheral sites of inflammation, opioid peptides are released into a harsh milieu associated with an increase in temperature, low pH, and high proteolytic activity. Together, this microenvironment has been suggested to increase the activity of opioid peptide metabolism. Therefore, the proximity of immune cells and nerve fibers may be essential to produce adequate analgesic effects. Close associations between opioid-containing immune cells and peripheral nerve terminals have been observed. However, it is not yet determined whether these immune cells actually form synaptic-like contacts with peripheral sensory terminals and/or whether they secrete opioids in a paracrine manner. This review will provide novel insight into the peripheral mechanisms of immune-derived analgesia in inflammation, in particular, the importance of direct interactions between immune cells and the peripheral nervous system.

Troxis necrosis, a novel mechanism for drug-induced hepatitis secondary to immunomodulatory therapy

OBJECTIVES

A case of drug-induced hepatitis mediated by troxis necrosis, a form of autoimmune hepatitis, is described.

METHODS

Clinical data, light and electron microscopy of an ultrasound-guided core needle liver biopsy specimen, were examined to investigate the cause of transaminitis in a 26year old male patient on Cellcept and Plaquenil for the treatment of lupus erythematosus. A systematic PUBMED review of troxis necrosis as the underlying mechanism for drug-induced hepatitis was performed.

RESULTS

Liver function tests (LFTs) were significant for elevated AST (305) and ALT (174); the autoimmune workup was significant for anti-ANA positivity and α-SMA negativity. On light microscopy, the liver biopsy shows focal areas of lymphocytic infiltrates surrounding and forming immunologic synapses with lobular hepatocytes, indicating lobular hepatitis of autoimmune nature. Electron microscopy confirmed the presence of immunologic synapses. Upon cessation of the offending medications, the LFTs returned to baseline with no further intervention. Literature search yielded 7 previously reported cases of drug-induced hepatitis mediated by troxis necrosis.

CONCLUSION

Troxis necrosis is a novel mechanism for drug-induced hepatitis, including immunomodulatory medications including a monoclonal anti-TWEAK antibody and Cellcept and Plaquenil, two widely used immunosuppression/anti-rejection medications.