Stage-dependent immunity orchestrates AQP4 antibody-guided NMOSD pathology: a role for netting neutrophils with resident memory T cells in situ.

Neuromyelitis optica spectrum disorder (NMOSD) is an autoimmune disease of the CNS characterized by the production of disease-specific autoantibodies against aquaporin-4 (AQP4) water channels. Animal model studies suggest that anti-AQP4 antibodies cause a loss of AQP4-expressing astrocytes, primarily via complement-dependent cytotoxicity. Nonetheless, several aspects of the disease remain unclear, including: how anti-AQP4 antibodies cross the blood-brain barrier from the periphery to the CNS; how NMOSD expands into longitudinally extensive transverse myelitis or optic neuritis; how multiphasic courses occur; and how to prevent attacks without depleting circulating anti-AQP4 antibodies, especially when employing B-cell-depleting therapies. To address these knowledge gaps, we conducted a comprehensive 'stage-dependent' investigation of immune cell elements in situ in human NMOSD lesions, based on neuropathological techniques for autopsied/biopsied CNS materials. The present study provided three major findings. First, activated or netting neutrophils and melanoma cell adhesion molecule-positive (MCAM+) helper T (TH) 17/cytotoxic T (TC) 17 cells are prominent, and the numbers of these correlate with the size of NMOSD lesions in the initial or early-active stages. Second, forkhead box P3-positive (FOXP3+) regulatory T (Treg) cells are recruited to NMOSD lesions during the initial, early-active or late-active stages, suggesting rapid suppression of proinflammatory autoimmune events in the active stages of NMOSD. Third, compartmentalized resident memory immune cells, including CD103+ tissue-resident memory T (TRM) cells with long-lasting inflammatory potential, are detected under "standby" conditions in all stages. Furthermore, CD103+ TRM cells express high levels of granzyme B/perforin-1 in the initial or early-active stages of NMOSD in situ. We infer that stage-dependent compartmentalized immune traits orchestrate the pathology of anti-AQP4 antibody-guided NMOSD in situ. Our work further suggests that targeting activated/netting neutrophils, MCAM+ TH17/TC17 cells, and CD103+ TRM cells, as well as promoting the expansion of FOXP3+ Treg cells, may be effective in treating and preventing relapses of NMOSD.

Herpes simplex encephalitis presenting as stroke-like symptoms with atypical MRI findings and lacking cerebrospinal fluid pleocytosis.

A 73-year-old woman presented with sudden onset of right hemiparesis and was diagnosed as having cerebral infarction on the basis of diffusion-weighted brain MRI, which demonstrated lesions in the left parietal cortex. On the 3rd day, the patient developed right upper limb myoclonus, aphasia, and disturbance of consciousness with high fever. On the 6th day, she was transferred to our hospital with suspected viral encephalitis, and treatment with acyclovir was started. By the 6th day, the lesions detected by MRI had expanded to the gyrus cinguli, insula and thalamus, but not to the temporal lobe. At that time, the CSF cell count was 8/µl, and this later increased to 17/µl by the 13th day. Although herpes simplex virus DNA was detected in the CSF on the 6th day, there was no evidence of CSF pleocytosis or temporal lobe abnormalities demonstrable by brain MRI throughout the whole follow-up period. This was very atypical case of herpes simplex encephalitis characterized by a stroke-like episode, atypical MRI findings, and absence of cerebrospinal fluid pleocytosis. It is important to be mindful that herpes simplex encephalitis (HSE) can have an atypical presentation, and that sufficient acyclovir treatment should be initiated until HSE can be ruled out.