Differential Diagnosis of Autoimmune Encephalitis from Infectious Lymphocytic Encephalitis by Analysing the Lymphocyte Subsets of Cerebrospinal Fluid

This study is aimed at investigating the lymphocyte subsets of cerebrospinal fluid (CSF) to provide possible differential diagnostic values and better understand the pathophysiological mechanism underlying autoimmune encephalitis (AE) and infectious lymphocytic encephalitis. A series of CD markers, including CD3/4/8/20 representing different types and developmental stages of lymphocytes, were used to count the corresponding subpopulations of CSF from clinical and laboratory confirmed cases of anti-N-methyl-D-aspartate receptor AE (NMDAR-AE), herpes simplex virus encephalitis (HSVE), and tuberculous meningitis (TBM). The percentages of lymphocytes observed and the CD4 : CD8 ratios were compared between the three groups. There were no significant differences of the percentage of total lymphocytes, CD3 cells, and CD4 cells of CSF among each group. However, there were strongly statistical differences of the CD4 : CD8 ratio in CSF of each group with 0.6 : 1 in NMDAR-AE, 0.9 : 1 in HSVE, and 3.2 : 1 in TBM. The percentage of CD20 B lymphocytes in NMDAR-AE was statistically higher than that of other groups. The distinct percentages of lymphocyte subpopulations of CSF appeared to be characteristic and could potentially serve as diagnostic indicators. Further verification and research will be necessary to clarify the significance and nature of CD4 : CD8 ratios and B lymphocytes in CSF between AE and the infectious lymphocytic encephalitis.