Cerebrospinal fluid T cell frequency is age-related: a case-control study of 435 children with inflammatory and non-inflammatory neurological disorders

Studies of cerebrospinal fluid (CSF) T cells in children are limited, dueespecially to the lack of control data. In adults, gamma/delta T cells (TCR-) residing in the intrathecal space are sometimes involved in neuroinflammation. To evaluate the possible role of T cells in paediatric neuroinflammation, we immunophenotyped cerebrospinal fluid (CSF) and blood lymphocytes using flow cytometry in a case-control study of 100 children with non-inflammatory neurological disorders (NIND), 312 with opsoclonus-myoclonus (OMS) and 23 with other inflammatory neurological disorders (OIND). In NIND, the negative correlation between CSF T cell frequency and patient age was striking: median frequency of 27% in infants and 3<bold></bold>3% in teens. Interindividual variations were largest in the youngest. There was no gender effect. In all OMS, after correcting for age, only a small effect of OMS severity remained. Measurement of markers for T cell activation [human leucocyte antigen D-related (HLA-DR)], maturation (CD45RA, CD45RO) or intracellular cytokine staining [interleukin (IL)-4, interferon (IFN)-] failed to discriminate OMS and NIND groups. Of seven OMS immunotherapies/combinations, none altered the frequency of total CSF T cells or subsets significantly. In OIND, the CSF T cell frequency was <10% for single samples of other paraneoplastic disorders [anti-neuronal nuclear antibody (ANNA)-1, PCA-1, teratoma-associated syndrome], cerebellar ataxia (post-infectious, ataxia-telangiectasia), acute disseminated encephalomyelitis, neuroborreliosis and encephalitis. This study provides new insights into CSF T cells in the paediatric population. Although their role in CSF remains elusive, the negative age correlation, resistance to immunotherapy and our age cut-off references for NIND are important findings for the design of future paediatric studies.