Little is known about the presence of dendritic cells in the human CNS. To investigate the occurrence of dendritic cells in the CSF, paired blood/CSF samples from patients with multiple sclerosis, acute optic neuritis, Lyme neuroborreliosis, other inflammatory neurological diseases and non-inflammatory neurological diseases were examined using flow cytometry. Almost all CSF samples contained myeloid (lin–CD11c+HLA-DR++CD123dim) and plasmacytoid (lin–CD11c–HLA-DR+CD123high) dendritic cells. In non-inflammatory neurological diseases, dendritic cells of either subset only constituted up to 1% of CSF mononuclear cells. Myeloid CSF dendritic cells were elevated in optic neuritis, neuroborreliosis and other inflammatory neurological disorders, while plasmacytoid dendritic cells were elevated in all neuroinflammatory conditions studied, with especially high numbers in neuroborreliosis. Numbers of CSF dendritic cells correlated with the common parameters of CNS inflammation. The myeloid dendritic cells in CSF expressed higher levels of HLA-DR, CD86, CD80 and CD40 than those in blood, whereas expression of these molecules by plasmacytoid dendritic cells was equal in blood and CSF. Both CSF and blood dendritic cells expressed the chemokine receptor CCR5. This is the first demonstration that dendritic cells are present in human CSF and that plasmacytoid dendritic cells are present in a non-lymphoid compartment. Myeloid and plasmacytoid dendritic cells in CSF may contribute to orchestration of the local immune responses.

Two subsets of dendritic cells are present in human cerebrospinal fluid

To demonstrate oligoclonal IgG bands (I) in unconcentrated cerebrospinal fluid, we used isoelectric focusing in agarose followed by protein transfer to cellulose nitrate membrane, double-antibody peroxidase labeling, and avidin-biotin amplification. I can be reliably seen after isoelectric focusing of 5-microL specimens containing 125 ng of IgG (25 mg/L). Thus the technique is more sensitive than others (e.g., silver staining) and more reliable than radioimmunofixation. When we used this technique with fluids from 62 patients with multiple sclerosis and infectious disease of the central nervous system, 84% displayed I, a percentage not increased when the same specimens were concentrated to 3.5 g of IgG per liter, examined by agarose isoelectric focusing, and stained with Coomassie Blue. Results for 53 patients with tension headache and psychoneurosis were all negative. By obviating the need to concentrate samples of cerebrospinal fluid the present method is a useful, sensitive alternative for demonstrating I.

Improved detection of oligoclonal IgG in cerebrospinal fluid by isoelectric focusing in agarose, double-antibody peroxidase labeling, and avidin-biotin amplification.

The intrathecal Ab response to Ag introduced into the normal brain has not been fully explored. Involvement of Ag-specific, peripheral B cells in an intrathecal response was studied using a normal rat model of Ag infusion through an indwelling cannula into defined brain sites, while maintaining a functionally intact blood-brain barrier. Specific Ab was detected in serum and cerebrospinal fluid. The intrathecal response is first detectable at day 14. Isoelectric focusing of cerebrospinal fluid reveals banding patterns consistent with local Ab production. To increase Ag-specific, circulating peripheral lymphocytes available for trafficking to Ag-stimulated brain and for enhancing intrathecal Ab synthesis, rats were preimmunized peripherally. Subsequently, Ag or saline (control) was infused through the cannula. Under this protocol, intrathecal synthesis is detectable earlier (day 5 postinfusion). Immunohistochemical studies at the infusion site assessed Ag-specific B cells, T cells, and activated APCs. Rats receiving peripheral preimmunization followed by Ag into caudate nucleus have far greater numbers of these cells, including plasma cells, within the infusion site compared with saline controls. Results confirm previous indirect evidence of intrathecal Ab synthesis in normal rat brain and provide the first direct evidence for B cell trafficking across normal brain barriers plus retention at the Ag deposition site. Our studies indicate that the normal brain microenvironment supports development of Ag-directed humoral immunity. We propose that immune privilege in normal brain is characterized by down-regulation of cell-mediated but not Ab immune responses within the central nervous system.

Antigen-Dependent Intrathecal Antibody Synthesis in the Normal Rat Brain: Tissue Entry and Local Retention of Antigen-Specific B Cells

Multiple Sclerosis (MS) is an inflammatory disease of the Central Nervous System with multifocal areas of demyelination. Although its etiology and pathogenesis remain controversial, several lines of evidence indicate that MS is mediated by a misdirected immune response against one or several myelin proteins. The involvement of diverse leukocyte subsets and their products in MS is still the subject of considerable debate. The emphasis on T cells has derived mainly from the detection of activated T cells in MS plaques and analogies with animal models of MS. Because of these observations cell-mediated immunity has dominated the research field of MS to this day. However, in recent years the role of B cells, plasma cells and immunoglobulins in MS have been re-examined, and current findings indicate that humoral immunity also plays a major role in disease pathogenesis. B cells and their products could exert several potential effects during the course of MS. Firstly, autoantibodies against specific myelin antigens could mediate damage to myelin membranes. Secondly, some studies suggest that natural autoantibodies could enhance remyelination. Thirdly, antibodies directed against myelin components can participate in anti-idiotypic networks, which may regulate the course of MS. Increased intrathecal immunoglobulin synthesis reflected by raised IgG indices and an oligoclonal pattern is the most common abnormality detected in MS patients. The introduction of more sensitive procedures for protein detection has allowed demonstrating oligoclonal bands (OCBs) in up to 95 % of patients with clinically definite MS. Although the presence of OCBs in CSF of MS patients is now well established as a sensitive laboratory test to support the clinical diagnosis, OCBs may be present in other disorders, including those not directly related to infection or abnormal immune response. Nevertheless, the pathogenesis of OCBs in MS is still obscure, and despite extensive research their antigenic target(s) have yet to be established. Therefore, a critical task is to identify the specificity of such target(s), thus providing significant clues about MS etiology. For this purpose, novel molecular immunologic strategies have been recently developed to offer alternative approaches to identify putative antigens recognized by antibodies present in MS patients. The elucidation of the mechanisms and target(s) responsible for the onset of MS has obvious implications for the further development of specific therapies.

Oligoclonal bands and antibody responses in multiple sclerosis.

• Unconcentrated cerebrospinal fluid (CSF) and serum samples from 1114 consecutive patients were examined for presence of oligoclonal IgG bands (OB) by agarose isoelectric focusing (AIF) followed by protein transfer to nitrocellulose membrane, immunolabeling, and avidinbiotin-peroxidase staining (avidin-biotin AIF). Oligoclonal bands were demonstrated in CSF from all 58 patients with multiple sclerosis (MS), eight of 29 with aseptic nervous sytem infections, and 9% of 1014 with other neurological disorders (OND) considered as noninflammatory at primary clinical evaluation. Comparative examination of all specimens in another laboratory by conventional AIF after concentration of CSF revealed lower frequencies of OB in all diagnostic groups. In addition to the high sensitivity of avidinbiotin AIF, which enables detection of OB by separation of 5 μL of unconcentrated CSF even when the CSF IgG level is around the lower normal range, the procedure also has optimal specificity since IgG exclusively is detected. Avidin-biotin AIF may be the method preferred for routine examination of CSF for OB. Demonstration of OB in CSF is valuable especially in MS, where, in contrast to diagnostic aids such as evoked potentials and neuroimaging, it establishes inflammatory type of nervous system involvements. Oligeclonal IgG bands in CSF from patients with OND reflect intrathecal immune response and should lead to investigations of infectious etiology.

Oligoclonal IgG Bands in Cerebrospinal Fluid: Principles for Demonstration and Interpretation Based on Findings in 1114 Neurological Patients

Agarose isoelectric focusing of unconcentrated CSF and radioimmunofixation for detection of oligoclonal bands in patients with multiple sclerosis and other neurological diseases.

V.K. Kostulas

Papers

Agarose isoelectric focusing of unconcentrated CSF and radioimmunofixation for detection of oligoclonal bands in patients with multiple sclerosis and other neurological diseases.