Anti-endothelial cell antibodies and circulating immune complexes in the sera of patients with multiple sclerosis

Sera from patients with multiple sclerosis (MS) were examined for anti-endothelial cell antibodies and immune complexes by enzyme-linked immunosorbent assays (ELISAs) using cultured brain endothelial cells and Raji cells respectively. The concentrations of immunoglobulin (Ig) G which bound to cerebral endothelial cells and of immune complexes were significantly increased in the sera of patients with MS, especially those with an exacerbation. The levels of IgG binding to endothelial cells were still increased in the sera of exacerbated MS patients after blocking Fc receptors compared to those of controls. These findings indicate that IgG binding to endothelial cells may be mediated via an immunologically specific antigen-antibody interaction. The results show that anti-endothelial cell antibodies and immune complexes are present in cases of MS and they may play a pathogenetic role in the blood-brain barrier (BBB) damage.     

Autoantibodies to each protein fraction extracted from cerebral endothelial cell membrane in the sera of patients with multiple sclerosis

Damage to the blood-brain barrier (BBB) occurs in multiple sclerosis (MS), probably due to an immunological mechanism. Anti-endothelial cell antibodies may play a pathogenetic role in the BBB damage. Our previous studies led us to search for which protein fraction extracted from cerebral endothelial cell membrane was reactive to antibodies in the sera of patients with MS. The antibodies to each protein fraction extracted from the rat cerebral endothelial cell membrane were studied in patients with MS, other neurological diseases and controls using an enzyme-linked immunosorbent assay (ELISA) method. The patients with active relapsing MS (P less than 0.01) displayed significantly higher levels of immunoglobulin G (IgG) binding to the endothelial cell membrane fraction than did the controls. The sera of the same patients (P less than 0.001) also showed significantly higher levels of antibodies to fraction I (8.0 kDa) than did the normal controls. The high levels of IgG binding to fraction II (11.0 kDa) and III (12.3 kDa) were significantly increased in the sera of patients with active relapsing MS compared to normal controls (P less than 0.01). The immune response to the protein fraction extracted from the cerebral endothelial cell membrane fraction may indicate a result of the BBB damage in the case of MS.     

Thrombomodulin in the sera of patients with multiple sclerosis and human lymphotropic virus type-1-associated myelopathy

Damage to the blood-brain barrier, which mainly consists of cerebral endothelial cells, has been demonstrated in multiple sclerosis (MS) clinically and histochemically. To investigate the endothelial cell damage, we evaluated the presence of soluble thrombomodulin in the sera of patients with MS and human T lymphotropic virus type-1-associated myelopathy (HAM) using an enzyme-linked immunosorbent assay. Serum thrombomodulin levels were significantly increased in patients with acute relapsing MS during an exacerbation and chronic progressive MS as compared with those of controls (P < 0.001, respectively). Patients with HAM also had higher serum levels of thrombomodulin than did controls (P < 0.001). There was significant difference between patients with HAM and seropositive non-HAM carriers (P < 0.01). These results suggest that the detection of serum thrombomodulin could be used as a marker of endothelial cell damage in inflammatory diseases such as MS and HAM.     

Soluble CD4 and CD8 in the peripheral blood of patients with multiple sclerosis and HTLV-1-associated myelopathy

We evaluated the presence of soluble (s) CD4 and sCD8, released from activated T cells, in the sera of patients with multiple sclerosis (MS) and human T lymphotropic virus type 1 (HTLV-1)-associated myelopathy (HAM) using an enzyme-linked immunosorbent assay (ELISA). In addition, peripheral blood T cell subsets in patients with MS and HAM were analyzed by single and two color flow cytometry. The serum level of sCD8 was significantly elevated in MS patients as compared with controls (p less than 0.001). Sera from patients with an exacerbation of acute relapsing MS showed a higher sCD8 level than the patients in remission or controls (p less than 0.01 and p less than 0.001, respectively). The serum levels of both sCD4 and sCD8 were also significantly elevated in patients with HAM (p less than 0.001 and p less than 0.001, respectively). In addition, a significantly increased serum level of soluble interleukin-2 receptor (sIL-2R) was found in patients with HAM as compared with that of controls (p less than 0.001). These observations suggest that CD8 cells may be activated in the peripheral blood of patients with MS and sCD8 may be related to clinical activity, but that both CD4 and CD8 cells may be activated in the peripheral blood of patients with HAM.     

Increased levels of soluble tumor necrosis factor receptor in patients with multiple sclerosis and HTLV-1-associated myelopathy

Tumor necrosis factor-α (TNF-α) is a potent mediator produced by activated T lymphocytes and macrophages, which may play a role in the pathogenesis and development of multiple sclerosis (MS) and HTLV-1-associated myelopathy (HAM). The first step in the induction of many biological effects elicited by TNF-α is its binding to specific cell surface receptors. A soluble form of TNF receptors (sTNF-R) can be detected in the body fluid. We measured sTNF-R levels in the sera and cerebrospinal fluid (CSF) of patients with either MS or HAM, and evaluated the correlation between this mediator and diseaseaactivity. The levels of sTNF-R in the sera and CSF of patients with MS were significantly increased compared with controls, particularly patients with acute relapsing MS during an exacerbation (P < 0.001). CSF levels of sTNF-R showed a strong correlation with those of TNF (r = 0.716, P < 0.001). Higher levels of sTNF-R in the sera of HAM patients were detected as compared with those of either controls (P < 0.001) or non-HAM carriers (P < 0.001). Patients with HAM exhibited significantly higher CSF levels of sTNF-R than those with other neurological diseases (P < 0.0001). These results suggest that the detection of sTNF-R in the sera and CSF may predict disease progression. Availability of such a marker wou ld be useful in monitoring disease activity.     

多发性硬化和格林-巴利综合征患者体液中TNF及IL-1水平与临床关系的研究

测定了多发性硬化(MS)和格林-巴利综合征(GBS)患者的细胞因子，发现活动的MS血清和脑脊液(CSF)TNF水平显著高于稳定的MS和对照组。GBS患者急性期CSF和血清TNF水平显著高于对照组及治疗后水平。另外，MS和GBS患者CSF的TNF水平均高于相应的血清水平。通过研究还发现MS和GBS组CSF的蛋白含量显著增高。此外，MS组CSF白细胞敷与CSF的TNF水平及CSF蛋白含量相关，且CSF蛋白含量与血清、CSF的TNF水平相关。这表明TNF一方面可能来源干鞘内的单个核细胞，另一方面由于血脑屏障受损可能来源于血液，另外还可能来源于神经肢质细胞及血管内皮细胞。TNF可能在炎性脱鞘病发病初期起作用。     

In vitro intercellular adhesion molecule-1 expression on brain endothelial cells in multiple sclerosis

To investigate the origin of intercellular adhesion molecule-1 (ICAM-1) and its expression on brain endothelial cells, we studied the expression in vitro of ICAM-1 on human brain endothelial cells after incubation of T cells from patients with multiple sclerosis (MS) using a histochemical technique and flow cytometry. We determined soluble forms of ICAM-1 (sICAM-1) in the supernatants after mixtures of brain endothelial cells and T cells from patients with MS using an enzyme-liked immunosorbent assay. Flow cytometric analysis showed that a number of ICAM-1-positive cells were significantly increased after incubation of brain endothelial cells with T cells from patients with acute relapsing MS during an exacerbation as compared with those of controls (P<0.01). Patients with acute relapsing MS during an exacerbation and chronic progressive MS exhibited higher levels of ICAM-1 in the supernatants of mixtures with brain endothelial cells and lymphocytes than those of controls (P<0.001 and P<0.01, respectively). These results suggest that lymphocytes from patients with acute relapsing MS during an exacerbation lead to an increased expression of ICAM-1 on the brain endothelial cells and add to evidence involving this adhesion molecule in the pathogenesis of MS.     

Sialic acid and fatty acid concentrations in lymphocytes, red blood cells and plasma from patients with multiple sclerosis

Lipids and constituents of lipids were isolated from peripheral blood lymphocytes (PBL), red blood cells (RBC), plasma and sera from 51 patients with multiple sclerosis (MS) and 51 controls, matched for age, sex and race. The amount of sialic acid released by incubation of intact PBL from MS patients was significantly lower (P less than 0.02) than that of the sialic acid from control lymphocytes. The amounts of sialic acid released by neuraminidase from intact RBC, on the other hand, did not differ significantly between the MS group and the control group. The concentrations of ganglioside sialic acid in PBL from MS and control groups did not vary significantly. Similarly the concentration of ganglioside sialic acid in RBC from MS patients was not significantly different from that in the controls. Analyses of the fatty acids isolated after alkaline methanolysis of the lipids from the PBL of MS patients and controls showed a small but significant decrease (P less than 0.01) in the relative percentage of linoleic acid in patients with MS. Determination of the ester-linked fatty acids in RBC lipids from patients with MS showed a significant decrease (P less than 0.001) in the relative percentage of linoleic acid and an increase (P less than 0.01) in palmitic plus palmitoleic acids compared to control values. The fatty acid composition of the plasma neutral lipids plus free fatty acids showed a very significant decrease (P much less than 0.001) in the relative percentage of linoleic acid, a small decrease (P less than 0.05) in arachidonic acid and significant increases in palmitic (P less than 0.001) and oleic acids (P less than 0.001) in MS, compared to controls. These results are suggestive of possible differences in metabolism of lipids between patients with MS and controls.     

Oligodendrocyte staining by multiple sclerosis serum is nonspecific.

The immunofluorescent staining properties of 65 serum samples from 54 patients with multiple sclerosis (MS), 63 samples from 55 patients with other neurological diseases (OND), and sera from 14 healthy normal individuals were examined on frozen sections of bovine and human brain. When tested on bovine brain sections, positive oligodendrocyte staining was present in 63% of MS sera, 43% of OND sera, and 29% of normal sera. The percentages were lower with human brain tissue. Astrocyte and myelin staining was common. F(ab')2 fragments purified from selected positive and negative MS and control sera gave no staining, though IgG fractions from the same sera prior to pepsin digestion gave positive staining. When tested against antihuman IgM and IgA conjugates, the same positive sera and their IgG-depleted globulin fractions gave minimal or no staining. These results indicate that oligodendrocyte staining is not specific for MS, is not due to specific antibody, and is probably the result of nonspecific binding to Fc receptors.     

Tumor necrosis factor and interleukin-1 in the CSF and sera of patients with multiple sclerosis

Serum and cerebrospinal fluid (CSF) from 31 patients with multiple sclerosis (MS) were examined to determine the levels of tumor necrosis factor (TNF) and interleukin (IL)-1 alpha (or IL-1 beta) by an enzyme-linked immunosorbent assay. TNF was detected in 29 (93.5%) of CSF from 31 cases of MS. TNF was also detectable in 100% of CSF from patients with acute relapsing MS in exacerbation. Patients with acute relapsing MS in exacerbation showed significantly higher CSF levels of TNF as compared with either those in remission or the controls (P less than 0.001 and P less than 0.0001, respectively). Increased levels of TNF were also detected in 35.5% of the MS sera, and especially in those with acute relapsing MS in exacerbation. Increased TNF levels were also frequent in the CSF and sera of patients with Guillain-Barré syndrome (GBS), which is also a demyelinating disease. No IL-1 alpha (or IL-1 beta) was detected in either CSF or sera of 31 MS patients. It is considered likely that TNF CSF levels may reflect disease activity in MS.     

CSF antibodies to myelin basic protein and to myelin-associated glycoprotein in multiple sclerosis. Evidence of the intrathecal production of antibodies

Cerebrospinal fluid (CSF) from 40 multiple sclerosis (MS) patients was tested by solid-phase radioimmunoassay (RIA) for ability to bind 2 common structural components of myelin and oligodendroglia, i.e., to bind myelin basic protein (MBP) and myelin-associated glycoprotein (MAG). To prevent the effect of differences in CSF IgG concentration on binding activity, the CSF samples were tested at equal IgG concentration 1 mg/ml. The mean binding activity to MBP and MAG was significantly higher than in control neurotics, respectively P less than or equal to 0.05 and P less than or equal to 0.001. In 33% of MS cases, CSF antibody against both antigens was found. Indirect data were obtained that autoantibodies whose antigens are associated with myelin-oligodendrocyte unit are produced locally within the central nervous system (CNS). Anti-MAG and anti-MBP CSF antibody activity was significantly higher, P less than or equal to 0.01 for both antibody specificity, in MS cases characterized by high IgG Index, greater than or equal to 0.70 = means + SD in the neurotic group, versus MS cases characterized by normal IgG Index (less than or equal to 0.70). Correlation coefficient between antibody activity and IgG Index values was 0.785 for anti-MBP antibody, and 0.400 for anti-MAG antibody. The importance of intrathecally produced antibody to MBP and MAG lies in the fact that it indicates an active humoral autoimmune process against a myelin-oligodendrocyte unit in which more than one autoantigen is involved.     

Abnormal regulation of IgG production in multiple sclerosis

After stimulation with pokeweed mitogen (PWM), peripheral blood mononuclear cells (MNC) from patients with active multiple sclerosis (MS) produced significantly more IgG (8595 ng per milliliter, p less than 0.01) then MNC from normal age-matched controls (5477 ng per milliliter), whereas those tested during stable periods produced less IgG (4076 ng per milliliter, p less than 0.01). Treatment of MNC with sodium periodate (SP) generated suppressor cells for PWM-driven IgG production in normal controls and in most of the stable MS patients but in only 26% of those during active disease, in whom an increase in IgG production was often seen. This suggests a deficiency of inducible suppressor T cells associated with a supranormal B-cell response to polyclonal activation; T lymphocytes obtained from MS patients during active episodes strongly suppressed IgG production by normal B lymphocytes, whereas their B cells often produced more IgG in the presence of normal T cells. In active MS, a relative B-cell unresponsiveness to activated suppressor T cells would leave helper signals unbalanced, thus leading to increased B-cell activation, which might deplete the pool of inducible suppressor cells for IgG production.     

Multiple sclerosis serum and cerebrospinal fluid immunoglobulin binding to fc receptors of oligodendrocytes

Suspensions of bovine oligodendrocytes were used to study the immunofluorescent staining properties of sera from multiple sclerosis (MS) patients and normal individuals. All sera (14 MS patients, 8 patients with other neurological diseases, and 11 normal individuals) showed positive oligodendrocyte staining by indirect immunofluorescence. Staining persisted after extensive absorption of sera with bovine liver to remove nonspecific binding. Similar findings were obtained for cerebrospinal fluid from all 5 MS patients as well as all 5 patients with other neurological diseases. In additional studies to determine if binding is mediated by the Fc fragment of IgG, results were: (1) ultracentrifuged normal and MS sera failed to react with oligodendrocytes, (2) positive staining with oligodendrocytes was observed after heat aggregation of IgG, (3) ox red blood cells, complexed with antibody, reacted with oligodendrocytes to produce strong rosette formation, and (4) the rosette formation could be blocked by prior treatment of oligodendrocytes with heat-aggregated IgG. The studies fail to support a previous claim for specific binding of immunoglobulins to oligodendrocytes in MS. However, they confirm and extend previous findings that the binding of IgG to oligodendrocytes may not necessarily be an antigen-antibody reaction. Therefore, adherence reactions with a putative antibody must exclude Fc-mediated binding.     

Neuronal molecular mimicry in immune-mediated neurologic disease

Molecular mimicry is implicated in the pathogenesis of autoimmune diseases such as diabetes mellitus, rheumatoid arthritis, and multiple sclerosis (MS). Cellular and antibody-mediated immune responses to shared viral-host antigens have been associated with the development of disease in these patients. Patients infected with human T-lymphotropic virus type I (HTLV-I) develop HTLV-I-associated myelopathy/tropical spastic paraparesis (HAM/TSP), an immunemediated disorder of the central nervous system (CNS) that resembles some forms of MS. Damage to neuronal processes in the CNS of HAM/TSP patients is associated with an activated cellular and antibody-mediated immune response. In this study, IgG isolated from HAM/TSP patients was immunoreactive with uninfected neurons and this reactivity was HTLV-I specific. HAM/TSP IgG stained uninfected neurons in human CNS and cell lines but not nonneuronal cells. Neuronal western blots showed IgG reactivity with a single 33-kd band in all HAM/TSP patients tested. By contrast, no neuron-specific IgG reactivity could be demonstrated from HTLV-I seronegative controls and, more important, from HTLV-I seropositive, neurologically asymptomatic individuals. Both immunocytochemical staining and western blot reactivity were abolished by preincubating HAM/TSP IgG with HTLV-I protein lysate but not by control proteins. Staining of CNS tissue by a monoclonal antibody to HTLV-I tax (an immunodominant HTLV-I antigen) mimicked HAM/TSP IgG immunoreactivity. There was no staining by control antibodies. Absorption of HAM/TSP IgG with recombinant HTLV-I tax protein or preincubation of CNS tissue with the monoclonal antibody to HTLV-I tax abrogated the immunocytochemical and western blot reactivity of HAM/TSP IgG. Furthermore, in situ human IgG localized to neurons in HAM/TSP brain but not in normal brain. These data indicate that HAM/TSP patients develop an antibody response that targets uninfected neurons, yet reactivity is blocked by HTLV-I, suggesting viral-specific autoimmune reactivity to the CNS, the damaged target organ in HAM/TSP.     

Clinicoimmunological values of measurement of IgG-Fc receptor positive T cells in the patients with malignant brain tumors

It has recently been shown that human T-cell subpopulation can be identified functionally via surface receptors for Fc fragment of immunoglobulins. We detected peripheral blood T-cells bearing the Fc receptor for IgG molecules (T gamma cell) in patients with brain tumors who manifested a variety of immunological abnormalities. We also analyzed immunological values of T gamma cells which were thought to be suppressor and/or a part of killer T cells, comparing with other immunological parameters. The percentage of T gamma cells was significantly higher in patients with malignant brain tumors than in normal controls (6.54 +/- 1.6%). The values of T gamma cells in patients with glioma, metastatic brain tumor, benign brain tumor were 15.4 +/- 4.8%, 14.9 +/- 3.2%, and 8.1 +/- 3.7%, respectively. In the patients with glioma, the values increased in the uncontrolled group compared with the well-controlled group. Furthermore, the values were decreased by surgical removal of the tumor. On immunological study of T gamma cells in the patients with glioma, there was a definite correlation between the values of T gamma cells and ADCC activity. Furthermore, the T gamma cells in the patients showed higher ADCC activity than in normal controls. The values of T gamma cells also correlated with blastogenesis of the peripheral blood lymphocytes by PHA (r = -0.742, p less than 0.001) and Con A (r = -0.662, p less than 0.001). These results suggest that T gamma cells are playing two important roles in patients with glioma such as suppressor function and ADCC activity, and that these cells may change according to the tumor growth.(ABSTRACT TRUNCATED AT 250 WORDS)     

Enhanced adherence of endothelial cells to blood mononuclear cells in HAM/TSP]

We investigated the adhesion of blood mononuclear cells (MNC) isolated from patients with HTLV-1-associated myelopathy (HAM/TSP). MNC from HAM/TSP patients were significantly more adherent to activated endothelial monolayers than MNC from non-HAM/TSP (controls and HTLV-1 carriers) subjects. Blocking studies demonstrated that the adhesion molecules VLA-4 (CD49d), ICAM-1 (CD54), and L-selectin (CD62L) all contributed to increased binding. However, anti-ICAM-1 antibody was the most efficient in inhibiting binding HAM/TSP patients MNC to activated endothelial cells. Expression on MNC of molecules involved in adhesion was also studied by flow cytometry in HAM/TSP patients, HTLV-1 carriers, and healthy control subjects after two days culture without any mitogen. In HAM/TSP patients, L-selectin expression on CD4+ and CD8+ subsets was lower than in controls; interestingly, HAM/TSP patients had lower percentage of CD4+ subset expressing L-selectin than HTLV-1 carriers. The percentage of CD4+ and CD8+ cells expressing VLA-4 was found to be similar to controls in both HAM/TSP patients and HTLV-1 carriers. Following two days in culture without mitogen, the percentage of T cells expressing ICAM-1 increased in HAM/TSP and carriers, but not in controls. This study provides information regarding trans-endothelial migration of MNC across the blood brain barrier in HAM/TSP and suggests ICAM-1 and its counterpart molecule LAF-1 are involved in massive infiltration of lymphocytes observed in the spinal cord.     

Autoreactive IgG to intracellular proteins in sera of MS patients.

IgG binding to multiple protein constituents in lysates of Jurkat cells was detected by Western blot in sera of patients with multiple sclerosis (MS) and systemic lupus erythematosus (SLE). The distribution patterns of bands with sera tested against protein lysates from normal Jurkat cells or from Jurkat cells exposed to apoptosis or oxidative stress inducing conditions were similar in most patients, but with inter-individual differences. The number of bands with sera of both patient populations far exceeded those (0 or 2 bands) detected with sera of healthy controls. Proteinase K, RNase and DNase pre-treatment of cell lysates suggested a protein nature for all of the antigens and a ribonucleoprotein (RNP) nature for some of the antigens recognized by serum IgG of MS and SLE patients. Only two MS patients had positive anti-nuclear antibody (ANA) titers, while all of them had positive Western blots. In addition to similarities, dissimilarities were also recognized between the humoral immune responses in MS and SLE. No IgG molecules were detected against phosphorylated proteins in the sera of MS patients, while multiple phosphoproteins were recognized by IgG molecules of SLE patients in immunoprecipitation experiments. These data suggest that in addition to ANA, the sera of MS patients contain autoantibodies directed against multiple intracellular proteins. The protein recognition patterns of immunoglobulins in MS share similarities, but also have distinct features when compared to those in SLE. The biological significance of these autoantibodies in MS remains to be understood.     

T-cell interleukin-6 receptor binding in interferon-β-1b-treated multiple sclerosis patients

Multiple sclerosis (MS) is a T-cell-mediated autoimmune demyelinating disease of the central nervous system, associated with an altered cytokine network. We previously assayed peripheral blood T-lymphocyte binding for two prototypic cytokines, tumour necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6), and found that T cells from MS patients had significantly more TNF-alpha and IL-6 receptors than those from healthy controls. In the present work, paralleling a previous one on T-cell TNF-alpha binding, we studied the effect of interferon (IFN)-beta-1b treatment on T-lymphocyte IL-6 binding in patients with relapsing-remitting MS. T cells from MS patients had significantly (P < 0.001) higher amounts of IL-6 receptors than those from controls [292 +/- 6 vs. 228 +/- 8 (mean +/- SEM) receptors per cell, respectively], whereas the ligand-receptor affinity values were similar in the two groups [26.2 +/- 0.7 and 25.7 +/- 0.4 (mean +/- SEM) pmoles/l, respectively]. After a 3-month IFN-beta-1b treatment, they showed a significant decrease in IL-6 binding [266 +/- 7 (mean +/- SEM) receptors per cell]. After 6 and 9 months, T-cell IL-6 B(max) values were even lower [258 +/- 8 and 251 +/- 8 (mean +/- SEM) receptors per cell]. Since an increased IL-6 binding might be linked to a lymphocyte activation, our data give further support for an enhanced immune response in patients with MS. Our data seem to demonstrate that the major effects of IFN-beta-1b treatment result in a decrease of T-cell activation.     

Binding properties of cerebrospinal fluid IgG in multiple sclerosis and other neurological diseases

A solid phase radioimmunoassay (RIA) was used to detect antibodies to myelin or myelin basic protein (MBP) in the cerebrospinal fluid (CSF) of patients with multiple sclerosis (MS) or other neurological diseases (OND). When measured at the same IgG concentration, MS samples had higher binding values than OND against myelin, but not against MBP. Using F(ab')2 fragments purified from pools of MS and OND CSF there was no difference in binding to myelin between MS and OND samples. These results indicate that anti-MBP antibodies are nt a feature of MS and binding of CSF IgG to myelin is not due to specific antibody, but is probably the result of non-specific binding to Fc receptors.     

Antibody titers to HTLV-I-p40tax protein and gag-env hybrid protein in HTLV-I-associated myelopathy/tropical spastic paraparesis: correlation with increased HTLV-I proviral DNA load.

We studied the relationship between antibody titers to recombinant HTLV-I p40tax protein and gag-env hybrid protein in serum (by an enzyme-linked immunosorbent assay) and HTLV-I proviral DNA load in peripheral blood mononuclear cells (by a quantitative polymerase chain reaction method) in 18 patients with HTLV-I-associated myelopathy (HAM)/tropical spastic paraparesis (TSP), 17 HTLV-I carriers without HAM/TSP and 16 HTLV-I uninfected controls. The IgG and IgA antibody titers to either of the proteins correlated significantly with the HTLV-I pX (coding p40tax protein) and pol DNA amounts in HTLV-I infected subjects. HAM/TSP patients had significantly higher titers of IgG and IgA antibodies to the HTLV-I proteins than did the HTLV-I carriers without HAM/TSP. While the IgM antibodies to the HTLV-I proteins were found in only 6% of HTLV-I carriers without HAM/TSP, they were found in 40% of HAM/TSP patients, especially those having both a high HTLV-I proviral DNA load and high titers of the IgG and IgA antibodies. HAM/TSP patients with the IgM antibodies had a tendency to deteriorate more frequently on the Kurtzke's disability status scale and magnetic resonance imaging of the brain (leukoencephalopathy) than did those without in the two-year follow-up. Thus, the presence of IgM antibody and high titers of IgG and IgA antibodies to the HTLV-I proteins, together with the increased HTLV-I proviral DNA load, appears to distinguish HAM/TSP patients from HTLV-I carriers without HAM/TSP.