Leukocyte trafficking in free-flowing cerebrospinal fluid of normal rhesus macaques (Macaca mulatta)

The cerebrospinal fluid immune cell landscape in animal models of multiple sclerosis

The fluid compartment surrounding the central nervous system (CNS) is a unique source of immune cells capable of reflecting the pathophysiology of neurologic diseases. While human clinical and experimental studies often employ cerebrospinal fluid (CSF) analysis, assessment of CSF in animal models of disease are wholly uncommon, particularly in examining the cellular component. Barriers to routine assessment of CSF in animal models of multiple sclerosis (MS) include limited sample volume, blood contamination, and lack of feasible longitudinal approaches. The few studies characterizing CSF immune cells in animal models of MS are largely outdated, but recent work employing transcriptomics have been used to explore new concepts in CNS inflammation and MS. Absence of extensive CSF data from rodent and other systems has curbed the overall impact of experimental models of MS. Future approaches, including examination of CSF myeloid subsets, single cell transcriptomics incorporating antigen receptor sequencing, and use of diverse animal models, may serve to overcome current limitations and provide critical insights into the pathogenesis of, and therapeutic developments for, MS.

Flow cytometric cerebrospinal fluid analysis in children

Flow cytometry (FC) is of increasing importance for the analysis of cerebrospinal fluid (CSF) lymphocytes because of its ability to detect a large spectrum of cellular characteristics (granularity, volume, surface antigen expression) even in small amounts of cells. Data on CSF FC in children are very limited. Here, we summarize our 3-year experience of CSF FC routinely performed in pediatric patients with assumed inflammatory central nervous system (CNS) disease. Among 109 samples sent for analysis, flow cytometric detection of major leukocyte subsets was possible in 78% (85 out of 109), which exceeds the 31% rate of our retrospective microscopic pediatric control group. Apart from physiologic lymphocytes (100%) or monocytes (48%), 11 out of these 85 samples showed granulocytes, two showed proliferated monocytes, and nine displayed proliferated lymphocytes. In most children, the proliferated lymphocytes consisted of a polyclonal population of CD4+ and CD8+ T cells. Compared with literature data, eight children showed abnormally composed lymphocyte subsets (surface antigen expression) within the main lymphocyte population. However, none of these changes was specific for distinct diseases or allowed a distinction between patients with and without primary inflammatory processes. These data suggest that CSF FC may be the most effective modality to differentiate major CSF leukocyte subsets. At present, further differentiation of distinct cell populations, such as proliferated lymphocytes, is of limited clinical impact. This may, however, gain increasing interest in the future.

Quinolinic acid and lymphocyte subsets in the intrathecal compartment as biomarkers of SIV infection and simian AIDS

Cerebrospinal fluid (CSF) samples were collected from monkeys infected with SIVmac251 (SIV) or HIV-1/SIVmac chimeric viruses (SHIV(HXBc2) and SHIV(89.6P)) to investigate quinolinic acid (QUIN) levels in the intrathecal compartment. CSF levels of QUIN were elevated in the SIV-infected monkeys, especially in animals with end-stage disease, and in those infected with pathogenic SHIV(89.6P), but not after infection with the nonpathogenic construct SHIV(HXBc2). QUIN elevations occurred in association with reduced CD4+ and increased CD8+ lymphocytes, cellular alterations that were more pronounced in CSF than in the blood. These findings support the view that the intrathecal compartment provides a unique window on viral infection, and are in keeping with the a priori prediction that QUIN increases primarily in response to more pathogenic viral strains.

Psychological disturbance differentially alters CD4+ and CD8+ leukocytes in the blood and intrathecal compartments

To evaluate cellular changes in the intrathecal compartment in response to psychological stress, cerebrospinal fluid (CSF) and peripheral blood (PB) samples were obtained from rhesus monkeys under baseline and challenge conditions. Juvenile monkeys separated from their social companions overnight had elevated cortisol, increased polymorphonuclear (PMN), and fewer CD4+ and CD8+ leukocytes in PB. In contrast, in CSF there were more CD4+ and fewer CD8+ leukocytes, raising the CD4/CD8 ratio. Dexamethasone given intramuscularly caused similar hematological changes; i.e. neutrophilia and lymphocytopenia with fewer CD4+ and CD8+ leukocytes in PB. However, it did not induce similar changes in CSF, indicating that the stress-related shift of CD4+ leukocytes in the intrathecal compartment involves physiological processes beyond adrenocortical steroids.