IgM and IgG responses during chronic relapsing experimental allergic encephalomyelitis (r-EAE)

Estimation of intrathecal IgG synthesis: simulation of the risk of underestimation

Objective

The low level of passively diffused IgG through the blood–brain barrier is sufficient to blur the estimation of intrathecal IgG synthesis (ITS). Therefore, this estimation requires a mathematical calculation derived from empirical laws, but the range of normal values in healthy controls is wide enough to prevent a precise calculation. This study investigated the precision of various methods of ITS estimations and their application to two clinical situations: plasma exchange and immune suppression targeting ITS.

Methods

Based on a mathematical model of ITS, we constructed a population of healthy controls and applied a tunable ITS.

Results

We demonstrate the following results: underestimation of ITS is common at individual level but true ITS is well fitted by cohorts; Q_IgG increases after plasma exchange; IgG_Loc calculation based on Qlim falsely increases when Q_Alb decreases; the sample size required to demonstrate a decrease in ITS increases exponentially with larger Q_Alb.

Interpretation

Studies evaluating changes in ITS level should be adjusted to Q_Alb. Low amounts of ITS could be largely underestimated.

Oligoclonal IgG bands synthesized in the central nervous system are present in rats with experimental autoimmune encephalomyelitis

OBJECTIVE

Oligoclonal bands (OBs) in electrophoresis of cerebrospinal fluid (CSF) are present in multiple sclerosis and here is investigated whether these also occur in experimental autoimmune encephalomyelitis (EAE).

MATERIAL AND METHODS

Experimental autoimmune encephalomyelitis was induced in 42 DA rats after immunization with rat spinal chord homogenate and the occurrence of OBs were detected by electrophoresis of both sera and CSF. The relationship between disease symptoms, antibody response against myelin basic protein (MBP), myelin oligodendrocyte glycoprotein (MOG) and appearance of OBs was studied.

RESULTS

Development of CSF-specific OB was found to occur, 6 weeks after immunization, in seven of 42 rats. OB was detected in rats with an antibody response against MBP, whereas as a role no such bands were present in rats with an antibody response against MOG. Initially severe disease symptoms were correlated to a concomitant intense oligoclonal antibody response.

CONCLUSION

Cerebrospinal fluid-specific OB occurs in EAE. It is present in rats with an anti-MBP, but not in rats with an anti-MOG antibody response. A severe disease results in an intense oligoclonal antibody response, which might have an anti-inflammatory effect.

Persistent anti-myelin basic protein IgG antibody response in multiple sclerosis cerebrospinal fluid

Antibodies to myelin components, such as myelin basic protein (MBP), may play a role in pathogenesis of multiple sclerosis (MS) but results from determinations of anti-MBP antibodies are inconsistent. Enumeration of cells secreting antibodies represents a new approach to evaluate a specific antibody response regarding extent and localization, and reduces effects of e.g. antibody binding to target. Anti-MBP IgG antibody secreting cells were present in MS patients' cerebrospinal fluid (CSF) at a mean value of 1 per 833 cells, and they amounted to a mean value of about 2454 in the whole CSF compartment. Similar numbers were encountered in patients with other inflammatory neurological diseases (OIND). During follow-up, anti-MBP IgG antibody secreting cells persisted regarding frequency and numbers in MS, but decreased in OIND. Such cells were rarely detected in patients with tension headache. No correlations to clinical exacerbation of MS, disability or duration were discernable. In blood from MS and OIND patients, anti-MBP IgG antibody secreting cells were detected infrequently and at low numbers. The anti-MBP antibody response is strongly restricted to the IgG isotype. The anti-MBP IgG antibody response which is persistent and compartmentalized to the diseased organ, may be important for the development of MS.

The origin and specificity of intrathecal IgG in chronic relapsing experimental allergic encephalomyelitis

The source of IgG in the cerebrospinal fluid (CSF) in guinea pigs with chronic relapsing experimental allergic encephalomyelitis (CR-EAE) was investigated using quotient analysis of total IgG and albumin concentrations and by computing CSF-plasma ratios of specific IgG concentrations. Increased blood-CSF barrier (B-CSFB) permeability was shown by elevated albumin quotients in both relapse and remission phases of CR-EAE and intrathecal production of IgG was indicated by raised ratios of IgG to albumin in the CSF. Intrathecal IgG synthesis was greatest in guinea pigs which had little B-CSFB damage. When enzyme-linked immunosorbent assays (ELISA) for whole cord, myelin basic protein (MBP) or Mycobacterium tuberculosis were performed with CSF and plasma adjusted to the concentration of total IgG, the CSF/plasma ratios of ELISA results for specific antibodies were less then unity and ratios for whole cord and MBP were lower than those for M. tuberculosis. There was thus no evidence for a selective increase in the CSF of antibody specific either for the neuroantigens tested or for adjuvant components. The CSF-plasma ratios for each specific antibody were inversely correlated with the extent of total IgG intrathecal synthesis, suggesting that much of the antibody production within the CNS is the result of polyclonal B cell activation.

Autoantibody responses in the cerebrospinal fluid of guinea pigs with chronic relapsing experimental allergic encephalomyelitis

We report the use of the ELISA technique to measure IgG specific for whole cord, myelin, myelin basic protein and Mycobacterium tuberculosis in the cerebrospinal fluid (CSF) of Strain 13 guinea pigs in different stages of chronic relapsing experimental allergic encephalomyelitis (CR-EAE). Specific antibody levels to all 4 antigen preparations were related to the severity of clinical signs, with the highest levels of IgG in the CSF of guinea pigs in relapse or in stable chronic disease. Total IgG levels in the CSF, though elevated throughout the course of CR-EAE, did not show any association with the category of disease. Control animals inoculated with complete Freund's adjuvant (CFA) alone showed CSF IgG levels specific for M. tuberculosis that were not significantly different from those in animals with chronic EAE, indicating that CFA may itself induce a late-acting increase in blood-brain barrier permeability.

Plasma immunoglobulin responses and disease severity in chronic relapsing experimental allergic encephalomyelitis

Plasma IgG, IgA and IgM responses in various stages of chronic relapsing experimental allergic encephalomyelitis (CR-EAE) were investigated by ELISA and rocket immunoelectrophoresis. Autoantibody levels were elevated in acute EAE but immunoglobulin responses were maximal in chronic disease. Plasma IgG and IgA specific for the whole cord, myelin and MBP correlated closely with the clinical signs of post-acute disease; in age-matched groups, levels were lower in animals in remission or with no further disease than in those in relapse or with a stable chronic disease course. Sequential sampling revealed a significant increase in neuroantigen-specific IgG (with MBP as the dominant autoantigen) during the onset of a relapse. Lipid-specific antibody levels were raised throughout CR-EAE but constituted only a small proportion of the total response against neural antigens. Determination of total immunoglobulin concentrations suggested a general suppression of IgG responses in guinea pigs in remission. The strong correlations found between antibody levels and the severity of chronic disease provide further evidence that antibody-mediated mechanisms can play a major role in the pathogenesis of CR-EAE.

Experimental allergic encephalomyelitis: the balance between encephalitogenic T lymphocytes and demyelinating antibodies determines size and structure of demyelinated lesions

The effect of a circulating monoclonal antibody recognizing an antigen located on the surface of myelin sheaths (myelin/oligodendroglia glycoprotein, MOG) on clinical and histopathological expression of experimental allergic encephalomyelitis (EAE) was tested in a model of EAE passively transferred by monospecific T lymphocytes. Intravenous injection of anti-MOG antibody at the onset of the disease massively augmented clinical impairment as well as primary demyelination. The structure of the CNS lesions depended on the balance between encephalitogenic T cells and anti-MOG antibody: when EAE was induced with high numbers of T cells, circulating anti-MOG antibody resulted in ubiquitous perivenous demyelination in the spinal cord and medulla oblongata. On the contrary, focal confluent demyelinated lesions were observed in animals injected with low numbers of T cells (even as few as 10(4] and anti-MOG antibody. Our studies, thus, indicate that the formation of inflammatory demyelinating lesions may be due to a synergistic action of cellular and humoral immune mechanisms.

T-lymphocyte subsets, functional deficits, and morphology in sciatic nerves during experimental allergic neuritis

Conduction velocities, demyelination, "macrophage/dendritic" cells, different sets of T-lymphocytes, and immunoglobulins were estimated in sciatic nerves during various phases of experimental allergic neuritis in Lewis rats. Demyelination was minimal day 15 postimmunization (p.i.) when conduction velocity already was reduced, somewhat more pronounced day 17 p.i. when nerve conduction was blocked, and most pronounced day 23 p.i. when nerve conduction partially had recovered. This suggests a dissociation between the degree of demyelination and the functional deficits. Decrease of sciatic nerve conduction velocities coincided with endoneurial appearance of T-lymphocytes and "macrophage/dendritic" cells, as well as endoneurial immunoglobulins, day 15 p.i. Later partial functional recovery occurred in parallel with the disappearance of T-cells. The degree of functional deficits thus correlated with the number of endoneurial T-lymphocytes. T-cells may, directly or indirectly, initiate several of the disease components in experimental allergic neuritis, including the nerve conduction deficit.

Serum and cerebrospinal fluid antibodies against myelin basic protein and their IgG subclass distribution in multiple sclerosis

IgG class antibodies reactive with myelin basic protein (MBP) were determined by enzyme-linked immunosorbent assay (ELISA) in serum and cerebrospinal fluid (CSF) of 37 patients with multiple sclerosis and a control group of 32 patients with tension headache or psychoneurosis. Using standardised amounts of IgG from CSF and serum in ELISA, significantly higher mean antibody levels were found in CSF as well as in serum from the patients with multiple sclerosis. Ten (27%) of the multiple sclerosis CSF samples and 15 (41%) of the multiple sclerosis sera revealed anti MBP antibody levels exceeding 2 SD of the control group. Seven patients (19%) showed exclusive or higher levels of anti MBP antibodies in CSF, suggesting synthesis within the central nervous system. Analysis by ELISA for IgG subclasses of anti MBP antibodies revealed that they were restricted to IgG 1 in four patients and IgG 3 in one.

Peripheral neuropathy and monoclonal IgM with antibody activity against peripheral nerve myelin; effect of plasma exchange

Serum IgM antibodies directed against peripheral nerve myelin were demonstrated using enzyme-linked immunosorbent assay, mixed haemagglutination and indirect immunofluorescence in 3 patients with chronic polyneuropathy and monoclonal serum IgM. Isoelectric focusing followed by antigen immunofixation and autoradiography showed that the antimyelin antibodies co-migrated with the monoclonal IgM. Plasma exchange alone, without chemotherapy, proved beneficial in 2 patients. In one patient, plasma exchange was discontinued because of low IgG levels. Serum IgM and antimyelin antibodies decreased during plasma exchange and no increase beyond initial levels was noted after cessation of treatment.

Immunocytochemical identification and quantitation of mononuclear cells in the meninges during the development of chronic relapsing experimental allergic encephalomyelitis (CREAE) in the guinea pig

To investigate the role of mononuclear cells in the meninges at all stages of chronic relapsing experimental allergic encephalomyelitis, juvenile guinea pigs were inoculated with isogeneic spinal cord in Freund's complete adjuvant (FCA) in parallel with animals inoculated with FCA alone as age-matched controls. Cytospins were prepared of the meningeal inflammatory cells obtained by washing the brains of these animals. These cytospins were stained by indirect immunoperoxidase, using a panel of monoclonal antibodies (Mabs) recognizing "activated" macrophages (M phi s), Ia antigen, total T cells and a putatively T-cell-suppressor subset, and an antiserum against immunoglobulins. The inflammatory response was quantitated and the proportions of the different cell types were determined. It was found that the total number of infiltrating cells correlated with the neurological symptoms of the disease. "Activated" M phi s increased significantly during the disease, in line with clinical signs. The expression of the Ia antigen, found on both lymphocytes and M phi s, also appeared to correlate with the disease. There was no increase in putative T-suppressor-cells during remission but there was a significant rise in the proportion of both cells staining with anti-immunoglobulins and plasma cells during relapse.

In vitro synthesis of immunoglobulins and autoantibodies by lymphocytes from various body compartments during chronic relapsing experimental allergic encephalomyelitis

Mononuclear cells extracted from regional lymph nodes, blood, spleen and central nervous system of guinea pigs with chronic relapsing experimental allergic encephalomyelitis (r-EAE), adjuvant immunized and untreated controls were cultured for 16 h in microtitre plates, and culture supernatants were then used to measure IgG and IgM, as well as IgG class anti-myelin antibody production by enzyme-linked immunosorbent assays. Increased synthesis of these immunoglobulins and antibodies was found during the course of r-EAE both in intra- and extrathecal compartments. Long-term cultures carried out for 7 days gave similar results but anti-myelin, anti-myelin basic protein and IgG synthesis was most pronounced intrathecally. Agarose isoelectric focusing of supernatants from these cultures showed oligoclonal IgG. These findings indicate in vivo synthesis of autoantibodies within the target for immune attack and a partial sequestration of the immune response to this compartment.

Cerebrospinal fluid immunoglobulin abnormalities in systemic lupus erythematosus

Central nervous system (CNS) involvement is a common and important complication in systemic lupus erythematosus. The mechanisms for CNS involvement are poorly understood and reliable diagnostic procedures are lacking. Pairs of serum and cerebrospinal fluid (CSF) specimens from 17 patients with clinical and serological manifestations of systemic lupus erythematosus were analysed. All 11 patients with definite or suspect clinical CNS disorder revealed some kind of abnormality in the CSF, in contrast to three of seven systemic lupus erythematosus patients without CNS disorder. The most prominent findings in systemic lupus erythematosus patients with CNS disorder were immune aberrations with oligoclonal bands on agarose isoelectric focusing (AIF) and elevation of IgG and IgM index, probably reflecting intrathecal production of IgG and IgM respectively. Intrathecal production of antiviral antibodies was found in four of 12 patients by AIF followed by immunofixation and subsequent autoradiography. An enzyme-linked immunoabsorbent assay (ELISA) could not detect autoantibodies against structural brain antigens.