Blood-brain barrier damage restricts the reliability of quantitative formulae and isoelectric focusing in detecting intrathecally synthesized IgG

Kappa-index: Real-life evaluation of a new tool for multiple sclerosis diagnosis

The intrathecal production of oligoclonal immunoglobulin bands (OCB) is a prognostic factor for multiple sclerosis (MS) evolution in clinically isolated syndrome (CIS) patients and a diagnostic factor for MS. The kappa free light chain (K)-index represents a quantitative automated alternative to OCB. We retrospectively evaluated OCB and K-index results in 274 patients with MS (n = 48) or CIS (n = 29) at diagnosis, non-MS inflammatory central nervous diseases (n = 35), and non-inflammatory central/peripheral nervous diseases (n = 162). Several cut-offs were established: a pathophysiological cut-off (K-index: 3.3) useful for differential diagnosis (negative predictive value for MS >99%), an optimised cut-off (K-index: 9.1) with better sensitivity and equivalent specificity than OCB for the diagnosis of MS, and a high-risk cut-off (K-index: >55.0) allowing prediction of MS (specificity 100%). We developed a scaled interpretation of the K-index and we discuss the usefulness of testing OCB only when the K-index is positive >3.3 to obtain a better specificity.

IgG intrathecal synthesis in HIV-associated neurocognitive disorder (HAND) according to the HIV-1 subtypes and pattern of HIV RNA in CNS and plasma compartments

We hypothesized that humoral immunity stimulation in the CNS in HIV-1C patients would be lower than that in HIV-1B due to a defective Tat chemokine dimotif (C30C31) that might influence cellular trafficking and CNS inflammation. Sixty-eight paired CSF and blood samples from people with HIV (PWH), free of CNS opportunistic infections, were included, HIV-1B (n = 27), HIV-1C (n = 26), and HIV negative (n = 25). IgG intrathecal synthesis was assayed using quantitative and qualitative methods. IgG oligoclonal bands (OCB) in CSF were observed in 51% of PWH, comparable between HIV-1B and HIV-1C, as well as the medians of IgG intrathecal synthesis formulas. The group with HIV infection aviremic in CSF and blood showed 75% of OCB. There was a poor positive correlation between the IgG quotient and GDS. The impact of HIV-1 on IgG intrathecal production was not subtype dependent. Low-grade CNS intrathecal IgG production persists in HIV CNS infection even in PWH with CSF and blood HIV RNA controlled.

Elevated immunoglobulin levels in the cerebrospinal fluid from lupus-prone mice

The systemic autoimmune disease lupus erythematosus (SLE) is frequently accompanied by neuropsychiatric manifestations and brain lesions of unknown etiology. The MRL-lpr mice show behavioral dysfunction concurrent with progression of a lupus-like disease, thus providing a valuable model in understanding the pathogenesis of autoimmunity-induced CNS damage. Profound neurodegeneration in the limbic system of MRL-lpr mice is associated with cytotoxicity of their cerebrospinal fluid (CSF) to mature and immature neurons. We have recently shown that IgG-rich CSF fraction largely accounts for this effect. The present study examines IgG levels in serum and CSF, as well as the permeability of the blood-brain barrier in mice that differ in immune status, age, and brain morphology. In comparison to young MRL-lpr mice and age-matched congenic controls, a significant elevation of IgG and albumin levels were detected in the CSF of aged autoimmune MRL-lpr mice. Two-dimensional gel electrophoresis and MALDI-TOF MS confirmed elevation in IgG heavy and Ig light chain isoforms in the CSF. Increased permeability of the blood-brain barrier correlated with neurodegeneration (as revealed by Fluoro Jade B staining) in periventricular areas. Although the source and specificity of neuropathogenic antibodies remain to be determined, these results support the hypothesis that a breached blood-brain barrier and IgG molecules are involved in the etiology of CNS damage during SLE-like disease.

Intrathecal synthesis of interleukin-10 (IL-10) in viral and inflammatory diseases of the central nervous system

The intrathecal synthesis of interleukin 10 (IL-10) was investigated in 120 paired cerebrospinal fluid (CSF) and serum specimens from patients with various inflammatory and non-inflammatory diseases of the central nervous system (CNS). IL-10 was not demonstrated in the sera, but detectable levels were found in the CSF from: patients with acute viral ("aseptic") meningitis, but only within 48-72 h of symptom onset; human immunodeficiency virus type 1 (HIV)-infected patients with HIV-related encephalitis/leukoencephalopathy or cryptococcal meningitis; a patient with primary B cell lymphoma of the CNS, and a patient with encephalomeningeal sarcoidosis (in whom IL-10 was demonstrated in all CSF collected over a period of 6-months). In chronic meningeal infections/inflammations, IL-10 seems to be continuously produced within the CSF. Our findings suggest that IL-10, a cytokine which exerts many immunosuppressive actions, may play different immunomodulatory roles in CNS diseases; in particular, its intrathecal synthesis may explain why some infectious and inflammatory meningeal diseases may have slow development and chronic evolution.

Cerebrovascular and neurological disorders associated with antiphospholipid antibodies in CSF and serum

Paired serum and cerebrospinal fluid (CSF) samples from 70 patients with inflammatory and non-inflammatory neurological diseases, as well as 10 sera from patients with primary antiphospholipid syndrome (PAS), six of which presented with cerebrovascular ischemic syndromes, were studied for the presence of anticardiolipin antibodies (ACA) of the G and M classes. PAS sera and some selected paired CSF and serum specimens, were also analyzed for the presence of anti-phosphatidylserine (PS) and anti-phosphatidylethanolamine (PE) antibodies. High levels of IgG and IgM ACA were synthesized intrathecally only in patients with neurosyphilis. Patients with other infectious or inflammatory neurological diseases very rarely showed detectable levels of ACA in serum and/or CSF. ACA were found not only in patients with untreated PAS but also in the serum of 3/7 patients with migraine, thus confirming a relationship between ACA and vascular disorders. The search for PS and PE antibodies disclosed that in PAS patients the serum titers of these antibodies mirrored ACA IgG and IgM titers, while they were never found in the CSF.

Formulas for the quantitation of intrathecal IgG production. Their validity in the presence of blood-brain barrier damage and their utility in multiple sclerosis

There are several formulas for the quantitative determination of intrathecal IgG production: Reiber and Felgenhauer's formula (IgG(loc)), the Extended IgG index, Tourtellotte's formula (TOURT), Schuller and Sagar's formula (SCHULL), the IgG index, the Log IgG index, and Blennow and co-workers' formula (IGGPROD). To evaluate the utility of these formulas in the presence of blood-brain barrier (BBB) damage, we present the results from a study of serum and cerebrospinal fluid (CSF) samples from 125 healthy individuals, 18-88 years of age; 1072 consecutive patients without oligoclonal IgG bands (OCBs) in the CSF, 683 without BBB damage (CSF/S: albumin ratio < 9.8) and 389 with BBB damage (CSF/S albumin ratio 9.8-30); and 106 patients with definite multiple sclerosis (MS). The relation between the CSF/S albumin ratio and the CSF/S IgG ratio was remarkably linear in both healthy individuals (r = 0.95; P < 0.0001) and patients without oligoclonal bands in the CSF (r = 0.95; P < 0.0001). Therefore, IgG(loc) and the Extended IgG index, two formulas based on a nonlinear relation between the CSF/S albumin ratio and the CSF/S IgG ratio, yielded biased results (lower values) in the presence of BBB damage. TOURT and SCHULL also yielded biased (higher) values in the presence of BBB damage, probably because of incorrect constants in these formulas. There were no significant correlations between the CSF/S albumin ratio (i.e. the BBB function) and the IgG index or the Log IgG index, two dimensionless quotients for the detection of intrathecal IgG production, or between the CSF/S albumin ratio and IGGPROD, an empirical formula for the determination of intrathecal IgG production in mg/l.(ABSTRACT TRUNCATED AT 250 WORDS)

Immunological markers in the cerebrospinal fluid of HIV-1-infected children

Several immunological abnormalities were detected in the cerebrospinal fluid (CSF) of human immunodeficiency virus type 1 (HIV-1)-infected children. Intrathecal synthesis of immunoglobulins, free light chains (FLC), IL-1 beta, IL-6, and M-CSF were demonstrated both in asymptomatic children and children with subacute encephalopathy. Our findings further support the hypothesis that an immunopathological subclinical process within the central nervous system (CNS) may be an early manifestation of acquired immunodeficiency syndrome (AIDS). Cytokine detection in the CSF may represent a useful diagnostic tool in evaluating the outcome of HIV-1-infected patients.

The use of recombinant antigens in ELISA procedures for the quantification of intrathecally produced HIV-1-specific antibodies

An ELISA procedure is described for the quantification of intrathecally synthesized immunoglobulin G antibodies to human immunodeficiency virus (HIV) antigens. Recombinant p17, p24, endonuclease (END), reverse transcriptase (RT), a peptide from the transmembrane region of gp41 (ENV80) and a fusion protein containing HIV-1 and HIV-2 epitopes were compared with a commercially available ELISA. Using a reference serum, antibodies in serum and cerebrospinal fluid (CSF) to all of the antigens could be measured quantitatively in a reliable and reproducible fashion. Despite the fact that the titer varied up to 10(5)-fold between CSF and serum, interassay variability ranged from 3.87% for p17 to 8.41% for RT and intra-assay variability varied from 3.9% +/- 1.2% for p17 to 14.3% +/- 3.9% for the commercial ELISA. Antibody specificity indices (ASI) obtained by relating CSF/serum titers with reference to the corresponding IgG concentrations can be used to detect intrathecal synthesis of virus specific antibodies.

Laboratory investigation of cerebrospinal fluid proteins

Analysis of CSF proteins is useful in the diagnosis and management of neurological diseases in the following situations: 1. In inflammatory conditions when there is breakdown of blood-CSF barrier integrity. Meningitis is a medical emergency, with CSF total protein measurement being only a screening test. 2. In the detection of immune responses within the CNS. This is by far the most important application in a routine clinical setting, as it is now a firmly established criterion in the diagnosis of multiple sclerosis. Oligoclonal bands restricted to the CSF are the only reliable indicators of intrathecal immunoglobulin G synthesis and are practically always associated with inflammatory disease of the CNS. The method fo choice for detecting oligoclonal bands is isoelectric focusing with immunofixation. Quantitative measurement of IgG in the CSF is of no value in diagnostic pathology. 3. In destructive brain diseases when brain-specific proteins are released into the CSF, measurement of these proteins can give prognostic information.

Multiple sclerosis: relations between MRI and CT findings, cerebrospinal fluid parameters and clinical features

Cerebral MRI and CT findings were compared with various cerebrospinal fluid (CSF) parameters and clinical features in 75 patients with multiple sclerosis (MS). There were positive correlations between CSF albumin as a parameter of blood-brain barrier function and morphological parameters, namely the number of nonperiventricular foci and periventricular involvement demonstrated by MRI and ventricular enlargement as shown by CT. Apart from positive correlations between the number of nonperiventricular foci and CSF levels of IgA and IgG, including the IgG synthetic rate, no other correlations were found between CSF parameters (leucocyte count and immunoglobulin concentrations) and morphological findings. The unremitting-progressive type of MS was distinguished from the relapsing-remitting form by a lower CSF leucocyte count and a higher degree of disability, but there was no difference between the morphological findings in the two forms. Positive correlations were found between degree of disability and both periventricular involvement in the MRI and CT evidence of ventricular enlargement. In terms of correlations with the duration of disease, cerebral MRI proved to be far superior to CSF evaluations.

Measurement of intraocular IgA and IgM synthesis and filtration through the blood-aqueous barrier in cataract patients

The authors have tested two formulas by means of which the filtrated and the intraocularly (intrathecally) synthesized fraction of particular protein can be distinguished. The laser nephelometric method was applied to determine the serum (IgG, IgA, IgM, C3, albumin), aqueous humor (IgA, IgM, albumin) and CSF (IgG, IgM, C3, albumin) protein values in 42 subjects to test two models in physiological conditions. It was confirmed that the best results were achieved using the formula after Stambuk. Computer simulation performed to compare the formulas after Stambuk and Reiber & Felgenhauer showed a strong correlation (r greater than 0.98) between the calculated filtrated fractions of both models in a wide range of different barrier permeabilities. Laser nephelometry proved to be a useful method to determine low IgA and IgM values in aqueous humor.

Experimental allergic encephalomyelitis in the monkey: humoral immunity and blood-brain barrier function

Acute monophasic experimental autoimmune encephalomyelitis (AMEAE) was induced in 5 Macacus cynomolgus monkeys. Serum and cerebrospinal fluid (CSF) paired samples were collected before and four weeks after immunization, time of complete development of AMEAE clinical picture. After immunization the CSF/serum albumin ratio and the IgG index were markedly increased. Agarose isoelectric focusing (AIEF) followed by immunofixation revealed faint IgG oligoclonal bands in both serum and CSF of all monkeys, which became more evident after Kappa and Lambda assessment. Intrathecal synthesis of IgG oligoclonal bands was detected in only one CSF. Affinity-driven immunoblotting failed to detect anti-myelin basic protein (MBP) oligoclonal IgG. No free light chain (FLC) patterns or IgA and IgM oligoclonal bands were detected.

Immune activation in multiple sclerosis: study of IL-2, sIL-2R, and gamma-IFN levels in serum and cerebrospinal fluid

Serum and cerebrospinal fluid (CSF) levels of interleukin-2 (IL-2), soluble IL-2 receptor (sIL-2R), and gamma-interferon (gamma-IFN) were measured in multiple sclerosis (MS) patients, human immunodeficiency virus type 1 (HIV-1)-infected patients and normal controls (NC). Increased levels of both IL-2 and sIL-2R were found in MS serum. Moreover, 11 of 50 MS patients showed detectable levels of IL-2 in the CSF. HIV-1-infected patients had increased levels of sIL-2R in serum and, less frequently, in the CSF. gamma-IFN was never detected in serum and CSF of all the patients studied. These findings confirm preliminary reports, further stress a systemic T-cell activation in MS, and support the hypothesis that an immunologic disorder exists in such patients.

Human immunodeficiency virus type 1 (HIV-1) infection of the central nervous system: an evaluation of cytokines in cerebrospinal fluid

Cytokines play an important role not only for initiation of immune reactivity but also for development of tissue injury. Of 38 patients infected with human immunodeficiency virus type 1 (HIV-1) interleukin-1 beta (IL-1 beta) and interleukin-6 (IL-6) were identified in cerebrospinal fluid (CSF) of 22 (58%) and 16 (42%) patients, respectively. Among the IL-1 beta- and IL-6-positive CSF were eight of 15 HIV-1 patients with no clinical signs of central nervous system involvement and four of five patients with acquired immunodeficiency syndrome (AIDS) dementia complex. The presence of IL-6 was often associated with IL-1 beta and soluble interleukin-2 receptor in CSF as well as with intrathecal IgG synthesis. In none of the CSF samples tumor necrosis factor-alpha or interleukin-2 was detected.

Tumor necrosis factor alpha (TNF alpha) and neurological diseases. Failure in detecting TNF alpha in the cerebrospinal fluid from patients with multiple sclerosis, AIDS dementia complex, and brain tumours

The presence of tumor necrosis factor alpha (TNF alpha)/cachectin was investigated in 180 paired cerebrospinal fluid (CSF) and serum samples from patients with neurological diseases, and in five paired CSF and serum samples of Macaca cynomolgus monkeys with acute monophasic experimental autoimmune encephalomyelitis (AMEAE). TNF alpha was never detected in human CSF, even when an extensive demyelination was documented (active multiple sclerosis, acquired immunodeficiency syndrome (AIDS) dementia complex). Only one Macaca with AMEAE had detectable levels of TNF alpha in CSF but not in serum, suggesting an intrathecal synthesis of this cytokine in AMEAE.