Multiple Sclerosis: Cells Secreting Antibodies Against Myelin-Associated Glycoprotein are Present in Cerebrospinal Fluid

We evaluated the B-cell response in cerebrospinal fluid (CSF) and blood by enumerating cells secreting antibodies to myelin-associated glycoprotein (MAG) and, for reference, to myelin basic protein (MBP), two myelin components which may constitute targets for autoimmune attack in multiple sclerosis (MS). Among 25 untreated MS patients, 12 had cells in CSF secreting anti-MAG IgG antibodies (mean value 1 per 1429 CSF cells) and three also had cells secreting anti-MAG antibodies of the IgM isotype but at lower levels. In CSF from 2 out of 10 MS patients examined, anti-MAG and anti-MBP IgG antibody-secreting cells were present concurrently. Antibody-secreting cells were less frequent in blood and bone marrow, reflecting compartmentalization to CSF. Anti-MAG antibody-secreting cells were found in CSF from only 1 out of 27 control patients. The intrathecal production of anti-MAG and anti-MBP antibodies may be important in the pathogenesis of MS.     

Cells producing antibodies specific for myelin basic protein region 70-89 are predominant in cerebrospinal fluid from patients with multiple sclerosis.

Cells secreting antibodies against guinea pig myelin and synthetic myelin basic protein (MBP) peptides were evaluated in cerebrospinal fluid (CSF) and blood from patients with multiple sclerosis (MS) and a variety of other neurological diseases (OND). The peptides used, reproducing amino acid sequences 1-20, 70-89, 108-126, or 157-166 of MBP, were selected on the basis of their hydrophilic and encephalitogenic properties. Low numbers of cells secreting IgG antibodies against myelin or each of the MBP peptides (about 1 per 50,000) were detected in peripheral blood, with no difference between MS and OND. In CSF, cells secreting IgG antibodies to MBP 70-89 were more frequently (p = 0.007) detected in patients with MS (1/380 IgG-secreting cells on average) than in patients with OND (1/2083 IgG-secreting cells on average). The frequencies of cells secreting antibodies against myelin or the three other MBP peptides were similar in MS and OND. Thus, evaluation of B cell immunity at the cellular level indicates that MBP 70-89 is an immunodominant B cell epitope in MS. It is not clear whether this intrathecal anti-MBP 70-89 IgG antibody response has any pathogenetic relevance in MS or is the result of myelin breakdown.     

T Cells Recognizing Multiple Peptides of Myelin Basic Protein are Found in Blood and Enriched in Cerebrospinal Fluid in Optic Neuritis and Multiple Sclerosis

The cause of multiple sclerosis (MS) is unknown. Recently reported abnormal T-cell responses to several myelin proteins and myelin basic protein (MBP) peptides in peripheral blood constitute one line of evidence that autoimmune mechanisms could be involved in the pathogenesis of the disease. Monosymptomatic unilateral optic neuritis (ON) is a common first manifestation of MS and important to examine for a possible restriction of the T-cell repertoire early in the disease. T-cell activities to MBP and the MBP amino acid sequences 63–88, 110–128 and 148–165 were examined by short-term cultures of mononuclear cells from cerebrospinal fluid (CSF) and blood in the presence of these antigens, and subsequent detection and counting of antigen-specific T cells that responded by interferon-gamma (IFN-γ) secretion. Most patients with MS and ON had MBP and MBP peptide-reactive T cells in CSF, amounting to mean values of between about 1 per 2000 and 1 per 7000 CSF cells and without immunodominance for any of the peptides. Numbers were 10-fold to 100-fold lower in the patients' blood. Values were similar in ON and MS, and no evidence was obtained for a more restricted T-cell repertoire in ON. The MBP peptide-recognizing T-cell repertoire was different in CSF than in blood in individual patients with ON and MS, thereby giving further evidence for an autonomy of the autoimmune T-cell response in the CSF compartment. No relations were observed between numbers of autoreactive T cells and presence of oligoclonal IgG bands in CSF or abnormalities on magnetic resonance imaging of the brain in ON or clinical variables of MS. The high numbers of MBP and MBP peptide-reactive T cells could play a role in the pathogenesis of ON via secretion of effector molecules, one of them being IFN-γ, as well as in the transfer of ON to MS.     

T cells from multiple sclerosis patients recognize multiple epitopes on Self-IgG

The highly diversified variable regions of immunoglobulin (Ig) molecules contain immunogenic determinants denoted idiotopes. We have previously reported that T cells from multiple sclerosis (MS) patients recognize IgG from autologous cerebrospinal fluid (CSF), and mapped a T-cell epitope to an IgG idiotope. To test the ability of CSF IgG molecules to elicit a broad polyclonal T-cell response in MS, we have analysed T-cell responses in the blood and CSF against idiotope peptides spanning complementarity determining region (CDR) 3 and somatic mutations within the variable regions of monoclonal CSF IgG. Consistent with a diversified idiotope-specific T-cell repertoire, CD4(+) T cells from both patients recognized several idiotope peptides presented by HLA-DR molecules. Mutations were critical for T-cell recognition, as T cells specific for a mutated CDR1 peptide did not recognize corresponding germline-encoded peptides. One T-cell clone recognized both an idiotope peptide and the B-cell clone expressing this idiotope, compatible with endogenous processing and presentation of this idiotope by B cells. These results suggest that mutated CSF IgG from MS patients carry several T-cell epitopes, which could mediate intrathecal IgG production and inflammation in MS through idiotope-driven T-B-cell collaboration.     

Cord blood contains cells secreting antibodies to nervous system components.

Umbilical cord blood of newborns and peripheral blood of healthy adults were investigated by an immunospot assay for cells secreting IgG, IgA and IgM antibodies against myelin basic protein (MBP), proteolipid protein (PLP), myelin-associated glycoprotein (MAG) and myelin oligodendrocyte glycoprotein (MOG) which represent putative antigens for an autoimmune attack in multiple sclerosis (MS) and against acetylcholine receptor (AChR) which is considered an important autoantigen in myasthenia gravis. Cells secreting antibodies against one or more of these autoantigens were detected in 18 out of 24 newborns, and in eight out of 20 adults. Eight of the cord blood samples contained cells secreting antibodies of IgG, IgA and/or IgM isotypes to one antigen, five to two antigens, two to three antigens, two to four antigens, and one to five antigens. Most prominent were anti-MBP IgG antibody secreting cells which were detected in 13 newborns at a mean number of 1/20,000 cord blood cells, and in six adults at a mean number of 1/10(5) peripheral blood cells. Anti-AChR IgG antibody secreting cells were detected in four out of 12 newborns versus four out of 14 peripheral blood specimens, at mean values of 1/10(5) cells in both instances. Cells secreting autoantibodies of IgA and IgM isotypes were less frequent both in cord blood and peripheral blood. The occurrence of nervous tissue autoantibody secreting cells in newborns must be related to a possible primary role of such autoantibodies in MS and myasthenia gravis.     

Cerebrospinal fluid myelin basic protein is frequently ordered but has little value: a test utilization study

Diagnosis of multiple sclerosis (MS) is facilitated by analyzing biochemical properties of cerebrospinal fluid (CSF). Oligoclonal bands (OCBs) and immunoglobulin G (IgG) index are well-established markers for evaluating patients suspected of having MS. Myelin basic protein (MBP) is also ordered frequently, but its usefulness remains questionable. OCB, IgG index, and MBP were measured in 16,690 consecutive CSF samples. Samples were divided into 2 groups based on MS status known (n = 71) or unknown (n = 16,118). Medical charts of the MS status known group were reviewed to determine their MS status. OCBs have a stronger association to IgG index results than does MBP. Importantly, MBP does not add a statistically significant increase in diagnostic sensitivity or specificity when used in combination with OCB and/or IgG index. The data indicate that MBP is an unnecessary and overused test.     

Cells of Cerebrospinal Fluid of Multiple Sclerosis Patients Secrete Antibodies to Myelin Basic Protein In Vitro

To characterize the role of B lymphocytes in the pathogenesis of Multiple Sclerosis (MS), we have isolated mononuclear cells from cerebrospinal fluid (CSF) and stimulated them with a polyclonal B-cell mitogen (pokeweed mitogen). This study has been done with MS patients selected for the occurrence of an acute attack in the course of the disease and with patients hospitalized for other neurological diseases. Five of the 11 MS patients had B lymphocytes producing in vitro antibodies (Abs) directed against purified human myelin basic protein (hMBP), as revealed by Western blot analysis. None of the 20 patients with other neurological diseases showed such a reactivity. The produced Abs recognized only 1 or 2 hMBP peptides without dominance for a certain peptide. This result emphasizes the presence of B cells producing Abs against MBP in CSF of MS patients and shows the interest of studying mononuclear cells of CSF as a good marker of the pathogenesis.     

Identification of three FcR-positive T cell subsets (T gamma, T mu and T gamma mu) in the cerebrospinal fluid of multiple sclerosis patients

Proportions of T cells and T cell subsets, as identified by their Fc receptors (FcR) for IgM and IgG (Tmu and T gamma), were determined in the peripheral blood lymphocyte (PBL) and cerebrospinal fluid (CSF) lymphocyte populations in patients with multiple sclerosis (MS). On average, MS patients had 79% total T cells (62% of which were T gamma, 66% Tmu) in CSF lymphocytes compared to 66% total T cells (30% T gamma, 63% Tmu) in PBL. Normal age- and sex-matched controls PBL had 74% total T cells (20% T gamma, 54% Tmu). By direct observation using an indirect immunofluorescence assay, 41% of the CSF T gamma cells in MS patients bore receptors for IgM; these cells were designated T gamma mu and, according to the double-marker analysis, did not seem to correlate with disease stage. In MS PBL, 20% of T gamma cells were T gamma mu compared to 9% in the control PBL T gamma population. Thus, MS patients had a higher proportion of total T cells, T gamma cells and T gamma mu cells in their CSF than in their peripheral blood and than those populations found in normal control blood. The significance of this T gamma mu population for the continuing disease state in MS is discussed.     

Bone Marrow Derived Cells Express Human T-Cell Lymphotropic Virus Type I (HTLV-I)-Related Antigens in Patients with Multiple Sclerosis

Mononuclear cells in peripheral blood (PB) and cerebrospinal fluid (CSF) of seven patients and lymph nodes of three patients with clinically definite multiple sclerosis (MS) expressed antigens that reacted with monoclonal antibodies (MoAb) specific for HTLV-I p19 and p24 gag proteins. The labelled cells were visualized with immunoperoxidase staining and indirect immunofluorescence and identified at the ultrastructural level with immunogold technique. The frequency of these cells was low, ranging from 0.1% to less than 0.01% in blood. In CSF it was approximately 10 times lower. Cells reacting with anti-p19 Ab were found in all MS samples, whereas cells reacting with anti-p24 Ab were found in 3 out of 6 blood samples and in 3 out of 7 CSF samples. All lymph nodes (3/3) obtained from MS patients contained cells that reacted with anti-HTLV-I. p19 and p24 Ab. Cells reacting with the same AB were detected in blood of one out of 12 healthy controls. Stained cells were irregular, distinctly larger than lymphocytes, and had abundant cytoplasm, suggesting that they may be monocytes/macrophages. Immunogold particles were located in vacuole-like structures in the cytoplasm. The presence in MS patients of cells that react with HTLV-I Ab indicates that a human retroviral genome is being expressed, and suggests that a virus may be present. Our data support a role for a human retrovirus in multiple sclerosis.     

Cells producing antibody to measles and herpes simplex virus in cerebrospinal fluid and blood of patients with multiple sclerosis and controls.

The B cell response against measles and herpes simplex virus (HSV) was evaluated in cerebrospinal fluid (CSF) and peripheral blood from patients with multiple sclerosis (MS) and controls by enumeration of cells secreting anti-measles and anti-HSV antibodies of IgG, IgA and IgM isotypes. We used a nitrocellulose immunospot assay which enables parallel enumeration of numbers of cells secreting total IgG, IgA and IgM. Anti-measles IgG antibody-secreting cells were present in CSF from 21 of 24 MS patients (mean 24 cells/10(4) mononuclear cells), and against HSV in CSF from seven of eight patients (mean 23/10(4) cells). No antibody-secreting cells were detectable in the patients' blood. Ten MS patients examined were negative for cells in CSF and blood producing anti-measles antibodies of IgA and IgM isotypes. Anti-measles IgG antibody secreting cells were also found in CSF from four of 18 controls, and anti-HSV IgG antibody-secreting cells in six of 13, especially in patients with subacute or chronic inflammatory nervous system diseases. Our results confirm that viral antibodies in MS are produced within CSF and that this B cell response is preferentially sequestered to this compartment. Whether this viral B cell response in MS reflects specific activation due to persistence of viral antigens or an epiphenomenon remains to be clarified.     

Effect of immunosuppressive therapy on humoral immune response in multiple sclerosis

The purpose of this study was to evaluate the effect of various therapeutic regimens on: 1) intrathecal IgG synthesis on the basis of IgG Index value, 2) oligoclonal IgG spectrum visualized by SDS-PAGE of unconcentrated CSF, 3) CSF antibody specific activity against MBP estimated by solid phase RIA and expressed in cpm/micrograms IgG, and 4) immune complex (CIC) level in the CSF estimated by C1q binding solid phase RIA. CSF antibody against Gal-C and ganglioside was also estimated. Patients with clinically definite MS were selected according to 4 therapeutic regimens: group 1, subjected to Mega-dose prednisone therapy (4000 mg over 54 days), group 2, subjected to moderate dose prednisone therapy, group 3 subjected to Mega-dose Solu-Medrol therapy (7500 mg over 10 days), and group 4, subjected to intravenous Cyclophosphamide therapy (4000 mg over 10 days). This last group was characterized by chronic progressive course of disease. Intrathecal IgG production was significantly reduced in all 4 groups as a result of therapy. More pronounced reduction was obtained in Mega-dose prednisone (p below 0.001) and CY (p below 0.001) treated group. Therapeutic regimens did not influence the IgG oligoclonal pattern. The moderate dose prednisone therapy and Mega-dose Solu-Medrol therapy on CSF IgG anti-MBP antibody specific activity were less effective than the Mega-dose prednisone medication. CY therapy did not influence anti-MBP antibody specific activity in MS group characterized by chronic progressive course of disease. The influence of therapeutic regimens on elevated CIC level in the CSF was insignificant. In our study CSF the anti-galactocerebroside antibody appeared to be of IgM class.     

Increased mRNA Expression of IL-10 in Mononuclear Cells in Multiple Sclerosis and Optic Neuritis

The inflammatory nature of multiple sclerosis ( MS ) implicates the participation of immunoregulatory cytokines, including the T_h2 related IL-10 . We describe the use of in situ hybridization with cDNA oligonucieotide probes to detect and enumerate mononuclear cells ( MNC ) expressing mRNA for IL-10 which is known to down-regulate Thl cell related cytokines such as interferon-γ. Expression of IL-10 was studied in blood MNC of MS and blood and cerebrospinal fluid ( CSF ) MNC of optic neuritis (ON) patients without culture and after culture in the presence of myelin basic protein ( MBP ), the control antigen acetylcholine receptor ( AChR ), and without antigen. Numbers of IL-10 mRNA expressing MNC were elevated in the MS patients' blood both when enumerated without culture and after culture with MBP. Control patients with myasthenia gravis had elevated numbers of AChR -reactive IL-10 mRNA expressing cells, while numbers of MBP -reactive IL-10 positive ceils did not difl'er from numbers registered in cells without antigen. Patients with ON , in many instances representing early MS, had IL-10 positive blood MNC that were elevated to the same extent as in clinically deflnite MS , and further increased in the CSF . ON patients examined within 1 month after onset had lower numbers of MBP induced IL-10 mRNA expressing blood MNC compared with patients examined later suggesting that IL-10 is related to the degree of inflammation and outcome in ON .     

T cell vaccination in multiple sclerosis patients with autologous CSF-derived activated T cells: results from a pilot study

Myelin-reactive T cells are considered to play an essential role in the pathogenesis of multiple sclerosis (MS), an autoimmune disease of the central nervous system. We have previously studied the effects of T cell vaccination (TCV), a procedure by which MS patients are immunized with attenuated autologous myelin basic protein (MBP)-reactive T cell clones. Because several myelin antigens are described as potential autoantigens for MS, T cell vaccines incorporating a broad panel of antimyelin reactivities may have therapeutic effects. Previous reports have shown an accumulation of activated T cells recognizing multiple myelin antigens in the cerebrospinal fluid (CSF) of MS patients. We conducted a pilot clinical trial of TCV with activated CD4+ T cells derived from CSF in five MS patients (four RR, one CP) to study safety, feasibility and immune effects of TCV. CSF lymphocytes were cultured in the presence of rIL-2 and depleted for CD8 cells. After 5-8 weeks CSF T cell lines (TCL) were almost pure TCR alpha beta+CD4+ cells of the Th1/Th0 type. The TCL showed reactivity to MBP, MOG and/or PLP as tested by Elispot and had a restricted clonality. Three immunizations with irradiated CSF vaccines (10 million cells) were administered with an interval of 2 months. The vaccinations were tolerated well and no toxicity or adverse effects were reported. The data from this small open-label study cannot be used to support efficacy. However, all patients remained clinically stable or had reduced EDSS with no relapses during or after the treatment. Proliferative responses against the CSF vaccine were observed in 3/5 patients. Anti-ergotypic responses were observed in all patients. Anti-MBP/PLP/MOG reactivities remained low or were reduced in all patients. Based on these encouraging results, we recently initiated a double-blind placebo-controlled trial with 60 MS patients to study the effects of TCV with CSF-derived vaccines in early RR MS patients.     

IgM, IgA and IgG producing cells in cerebrospinal fluid and peripheral blood in multiple sclerosis.

The protein A plaque assay was used to enumerate IgM, IgA and IgG producing cells per 20 X 10(3) lymphocytes in cerebrospinal fluid (CSF) and peripheral blood (PB) from 37 patients with multiple sclerosis (MS) and in PB from healthy controls. Fifty-seven percent of the MS patients displayed in CSF cells producing IgM, 70% IgA and 89% IgG. IgM or IgA producing cells predominated in CSF from 10 patients, IgG in 27. Immunoglobulin producing cells were often present when the corresponding CSF Ig index was normal, confirming that enumeration of Ig producing cells is a more sensitive variable of the intrathecal immune status. No Ig producing cells were found in CSF from four patients with tension headache, indicating absence of intrathecal Ig synthesis in healthy individuals. The patients with MS had higher numbers of IgM, IgA and IgG producing cells in PB than healthy controls, confirming occurrence of an extrathecal B cell response in MS. Active and stable MS patients did not differ regarding Ig producing cells in CSF nor in PB, which speaks in favour of continuous immune activity within as well as outside the CNS independent of clinical symptoms.     

Autoreactive T and B cells responding to myelin proteolipid protein in multiple sclerosis and controls.

The pathogenesis of multiple sclerosis (MS) could involve an autoimmune response to proteolipid protein (PLP). Immunization of experimental animals with this major myelin protein can lead to experimental allergic encephalomyelitis. To identify a possible role of PLP as target antigen in MS, we evaluated T cell immunity to PLP in blood and cerebrospinal fluid (CSF) from patients with MS and controls by counting cells which in response to PLP in short-term cultures secreted interferon-gamma. The PLP-specific B cell response was analyzed by counting cells secreting anti-PLP antibodies. PLP-reactive T cells were detected in blood of most MS patients (mean value 1 per 20,408 mononuclear cells), and at 41-fold higher numbers in CSF (mean 1 per 500 CSF cells). Anti-PLP IgG antibody-secreting cells were detected in blood from most MS patients (mean 1 per 30,303 cells), but such cells were 49-fold more frequent in CSF (mean 1 per 625 cells). PLP-reactive T and B cells were also detected in blood and CSF from control patients, but at much lower numbers. A strong and persistent autoimmune response to PLP as well as to other myelin proteins, enriched in CSF, is proposed to be pathogenetically important in MS.     

Expansion of CD5 - B cells in multiple sclerosis correlates with CD80 (B7-1) expression

The pathogenetic role of autoantibodies in multiple sclerosis (MS) is uncertain. CD5+ B cells commonly produce autoantibodies, but CD5 expression has also been implicated in B-cell tolerance. We studied B-cell subsets, anti-myelin protein antibody-secreting cells in cerebrospinal fluid (CSF) and a panel of serum autoantibodies in patients with clinically isolated syndromes (CIS), suggestive of MS and patients with clinically definite MS (CDMS). Patients with CDMS had a higher percentage of CD5- B cells in CSF than did control subjects (P = 0.02). CIS patients with immunoglobulin G (IgG) oligoclonal bands in CSF or multiple lesions on magnetic resonance imaging (MRI) had a higher percentage of CD5- B cells in CSF than did the remaining CIS patients (P = 0.03). The percentage of CD5- and CD80+ B cells correlated positively and the percentage of CD5+ B cells correlated negatively with the number of CSF cells secreting anti-myelin basic protein (anti-MBP) antibodies. The prevalence of serum autoantibodies was comparable in the three patient groups. We conclude that intrathecal expansion of CD5- B cells appears to be more characteristic in MS patients, and CD5+ B cells may be associated with a lower prevalence of anti-myelin antibody production.     

HLA DRB1*1501 and intrathecal inflammation in multiple sclerosis

CD4 T cells are considered to be pivotal in the pathogenesis of multiple sclerosis (MS), and the human leukocyte antigen (HLA) haplotype associated with DRB1*1501 confers susceptibility to MS in patients of Northern European descent. Some previous studies have suggested an association of DRB1*1501 with T- and B-cell reactivity to specific myelin protein peptides, other studies suggested an association with enhanced cytokine production or intrathecal immunoglobulin (Ig) synthesis. In order to further assess the role of DRB1*1501 in the pathogenesis of MS, we studied intrathecal inflammation and T-cell phenotypes in patients with possible onset symptoms or clinically definite MS. Presence of DRB1*1501 was associated with higher levels of cerebrospinal fluid (CSF) inflammation as assessed by IgG synthesis levels and higher levels of matrix metalloproteinase-9 activity. DRB1*1501-positive patients also had a lower percentage of T cells in CSF expressing HLA-DR without co-expressing CD25. These findings suggest that enhanced intrathecal inflammation and an altered T-cell activation status may be of importance in conferring the DRB1*1501-associated susceptibility to MS.     

Lymphocyte Subpopulations and IgG Concentrations in Cerebrospinal Fluid and Blood from Patients with Myasthenia Gravis

Twelve patients with myasthenia gravis (MG) were examined for cerebrospinal fluid (CSF) T lymphocytes and for peripheral blood lymphocyte subpopulations (E-, E_AET-, EA- and EAC-rosette-forming cells). The patients had a significantly increased percentage of CSF T cells (88.2±8.7%) when compared with controls (78.0±9.1%). Absolute concentrations of CSF T cells were not significantly increased. In peripheral blood no significant change in lymphocyte subpopulations was observed, but there was a slight leucocytosis in the patient group. The patients had increased CSF IgG concentrations, CSF IgG to protein ratio, and CSF to serum IgG ratio, indicating an intrathecal production of IgG. No oligoclonal bands could be demonstrated in the agarose gel electrophoresis. The two patients with thymoma had anti-muscle antibodies in CSF and serum, with ratios of 1:256 and 1:1024, respectively. Serum IgG levels were increased, but not significantly, in the patient group. These results suggest an involvement also of the central nervous system in some patients with MG.     

Studies on the Mechanism by Which Antigen-Specific IgG Suppresses Primary Antibody Responses: Evidence for Epitope Masking and Decreased Localization of Antigen in the Spleen

Immunoglobulin (IgG) has the ability to suppress the Ab response against the Ag to which it binds. Although the mechanism remains unclear, this phenomenon has physiological relevance and is used clinically in Rh prophylaxis. As suppression works well in mice lacking the inhibitory FcγRIIB, the two most likely explanations are that IgG masks epitopes and/or that IgG increases the clearance of Ag. In the present study, mice were immunized with sheep red blood cells (SRBC) to which the hapten 5-iodo-4-hydroxyl-3-nitrophenacetyl (NIP) was conjugated at high or low density and the ability of IgG anti-NIP to suppress the Ab response to NIP and SRBC was assayed. Only the NIP-specific response was suppressed when mice were immunized with SRBC-NIP_low, whereas both NIP- and SRBC-specific responses were suppressed when SRBC-NIP_high was used. This is best explained by epitope masking; at high epitope density, IgG also blocks neighbouring epitopes from recognition by B cells. We also examined the effects of IgG-mediated suppression on T-cell responses directly in vivo . While IgG anti-SRBC administered with sheep red blood cells ovalbumin (SRBC-OVA) almost completely suppressed the anti-SRBC and anti-OVA Ab responses, the OVA-specific T-cell response was still 50% of that observed in control mice. This is probably the result of decreased Ag exposure as IgG-bound SRBC were cleared faster from the bloodstream and were found at lower concentration in the spleen than unbound SRBC. These results suggest that both Ag clearance and epitope masking occurs during IgG-mediated suppression, but that under physiological circumstances epitope masking is the predominant mechanism.     

The Role of Immune Complexes Consisting of Myelin Basic Protein (MBP), Anti-MBP Antibodies and Complement in Promoting CD4+ T-cell Responses to MBP in Health and Multiple Sclerosis

Multiple sclerosis (MS) is an autoimmune condition characterized by degeneration of nerve fibre myelin sheets. A candidate autoantigen, myelin basic protein (MBP), has especially attracted attention. The presence of anti-MBP antibodies is a predictor of definite MS, but their role in the pathogenesis remains obscure. T cells have long been known to play a pivotal role in the pathogenesis of MS. Recently, an important role for B cells as autoantigen-presenting cells has been demonstrated in other autoimmune diseases, including rheumatoid arthritis and diabetes. The uptake of MBP by B cells and the presentation of MBP-derive peptides to T helper (Th) cells by B cells may be promoted by the formation of complement (C) activating immune complexes (ICs) between MBP and natural autoantibodies in healthy individuals and disease-associated anti-MBP antibodies in MS patients, respectively. We have investigated the formation of MBP-containing IC, the binding of MBP to B cells, the MBP-elicited induction of Th-cell and B-cell proliferation and the cytokine production in peripheral blood mononuclear cells (PBMCs) from healthy donors grown in the presence of intact or C-inactivated serum from healthy donors or patients with MS. While MBP did not induce measurable proliferation of B cells nor CD4⁺ T cells, we observed the production of TNF-α, IFN-γ and IL-10 by PBMC in response to incubation with MBP in the presence of sera from healthy controls as well as sera from MS patients. By contrast, no production of IL-2, IL-4 and IL-5 was detected. We are currently investigating the capability of MS sera to promote the formation of MBP-containing IC and thereby enhance the cytokine responses, by virtue of elevated anti-MBP contents.