EAE in the common marmoset Callithrix jacchus.

The common marmoset Callithrix jacchus is a primate phylogenetically close to humans which, when immunized with myelin proteins, is susceptible to a form of experimental autoimmune encephalomyelitis (EAE) that resembles multiple sclerosis (MS). Neuropathological features of marmoset EAE, including inflammation, demyelination and axonal injury, are strikingly similar to findings in the human disease and are the final result of a joint autoimmune attack by myelin-specific T and B cells. The molecular and functional similarity of the marmoset immune system, together with the availability of diagnostic tools that can be used in humans (such as magnetic resonance imaging), makes the marmoset EAE a unique model with which to evaluate the safety and efficacy of therapeutic strategies for the treatment of MS.

Central and peripheral nervous system complications following allogeneic bone marrow transplantation.

Although graft vs. host disease (GvHD) is a frequent complication of allogeneic bone marrow transplantation (BMT), involvement of the central and peripheral nervous systems (CNS and PNS, respectively) has not been demonstrated conclusively. Here, we report of a patient who, following allogeneic BMT for lymphoblastic T-cell lymphoma, suffered a syndrome characterized by self-remitting cerebellar and pyramidal signs associated with a progressive involvement of the peripheral nervous system (PNS). Clinical course and laboratory findings correlated with relapses of systemic GvDH, thus suggesting the possibility that involvement of CNS and PNS may be sustained by a similar pathogenic mechanism.

Demyelination and axonal damage in a non-human primate model of multiple sclerosis.

The demyelinating plaque is the paradigmatic lesion of multiple sclerosis (MS), but only recently attention has been given to axonal damage and to its role in the pathophysiology of disease. Albeit the possible relevance of axonal loss in MS and its experimental models, the amount and timing of axonal sufferance has been addressed only in experimental autoimmune encephalomyelitis (EAE) of rodents. In this report we observed that, in the marmoset model of EAE, axonal damage occurs early during the demyelinating process as assessed by immunoreactivity for amyloid precursor protein (APP) and non-phosphorylated neurofilaments (SMI-32 positive) detected mostly in early active lesions compared to late active and normal appearing white matter. The rare occurrence of morphological features of axonal transection, such as APP or SMI-32 positive spheroids and swellings, as well as an increase of neurofilament density in the demyelinated axons without accumulation of electron dense organelles or osmiophilic bodies, at electron microscopy, suggests that early axonal damage may be, at least in part, a reversible process. These findings are of relevance for the development of therapies, which can protect axons and enhance their function and survival.

Characterization of the response to myelin basic protein in a non human primate model for multiple sclerosis.

The common marmoset Callithrix jacchus (C. jacchus) is an outbred species characterized by a naturally occurring bone marrow chimerism and susceptibility to a form of experimental autoimmune encephalomyelitis (EAE) resembling multiple sclerosis (MS). T cell clones specific for the myelin antigen, myelin basic protein (MBP), can be derived from both naive and immunized marmosets and can adoptively transfer EAE to compatible chimeric siblings. Here, we demonstrate that several different antigenic determinants of MBP are recognized by these encephalitogenic T cell clones. Furthermore, PCR-based analysis of TCR Vbeta families does not show the preferential usage of any gene segment. Characterization of third complementarity determining regions (CDR3) fails to demonstrate a recurring motif characteristic of the T cell immune response to MBP in this species. Nevertheless, brief amino acid motifs are shared among marmoset clones and CDR3 sequences from MS samples. These data suggest that, due to its outbred condition, the C. jacchus marmoset mounts a diverse pathogenic response to MBP. However, the findings that certain CDR3 sequences are identically expressed in different animals, or by different T cell clones, suggest that MBP-specific T cell populations may be clonally expanded following chronic antigenic stimulation in vivo.

Myelin basic protein intramolecular spreading without disease progression in a patient with multiple sclerosis.

A case with stable multiple sclerosis (MS) and T cell responses which initially focused on peptide 16-38 of myelin basic protein (MBP) allowed us to investigate the dynamics of the MBP-specific T cell repertoire and its relationship with disease progression. Epitope mapping experiments and T cell receptor usage of MBP-reactive T cell lines (obtained at four distinct time points over a 7-year period) showed a spreading of the response. Transient expansions and persistence of T cells recognizing different MBP epitopes were also detected. The patient's expanded disability status scale and magnetic resonance imaging lesion load remained stable. Our case shows both persistent self-recognitions and determinant spreading in stable MS. This finding suggests that the relationship between dynamics of self-recognition and disease progression is highly complex.

Restricted immune responses lead to CNS demyelination and axonal damage.

Although autoreactive T-cells have a pivotal role in initiating the inflammatory process in experimental autoimmune encephalomyelitis (EAE) and multiple sclerosis (MS), recent evidence suggests a relevant role for autoantibodies specific for myelin proteins as well. To examine the role of B-cells in the cerebrospinal fluid of patients with MS, we analyzed the V(H) gene usage in ten MS patients by PCR technologies. Analysis of HCDR3 length revealed an oligoclonal accumulation of B-cells. Sequence analysis of the V(H)3 and V(H)4 gamma transcripts of two MS individuals demonstrated that this accumulation was related to the expansion and somatic diversification of a limited groups of B-cell clones. These findings are indicative of a chronic and intense antigenic stimulation occurring in the CNS. Animal models, such as EAE, are of particular importance in order to elucidate the pathogenetic effector mechanisms in autoimmune demyelination. In a non-human primate model of EAE, we describe that the immunodominant T-cell epitope is presented exclusively by a monomorphic DRB1 allele, suggesting that susceptibility to EAE may be linked to this unique restriction and, therefore, providing a possible mechanism for MHC linkage to diseases. Moreover, we report on the presence of inflammation, sharp demyelination and axonal damage in EAE induced with whole myelin as well as with recombinant myelin oligodendrocyte glycoprotein (MOG), but not with myelin basic protein alone. The presence of axonal pathology was supported by immunohistochemistry with anti-amyloid precursor protein and anti-non phosphorilated neurofilaments monoclonal antibodies within early active demyelinated plaques. These findings suggest that axonal damage may be an early event in the pathogenesis of autoimmune demyelinating diseases of the CNS and highlights the importance of animal models in which therapies targeting repair and axonal survival may be exploited.

Dynamics of the reactivity to MBP in multiple sclerosis.

Though many lines of evidence support the importance of myelin basic protein (MBP) in the pathogenesis of experimental autoimmune encephalomyelitis (EAE), its role in multiple sclerosis (MS) is still debated as well as the significance of epitope spreading in disease progression. We characterised the response to MBP in eight MS subjects and three of these were followed over time. In one case, the follow up lasted over a 6-year period. Clonal expansion, clonal persistence and epitope spreading against other MBP determinants was detected irrespective of disease course. In one patient we identified a novel T-cell receptor variable gene (BV28S2) which may be involved in the selection of MBP determinants, as suggested by experiments performed in the presence of mismatched antigen presenting cells (APC) between two subjects compatible for HLA-DR2 subtype but differing for the epitope recognised. Our findings do not sustain a role for the response to MBP effecting on clinical course and suggest that a novel TCR gene may be involved in the recognition of unusual self antigens.

A major influence of the T cell receptor repertoire as compared to antigen processing-presentation in the selection of myelin basic protein epitopes in multiple sclerosis.

We selected two multiple sclerosis (MS) patients, compatible for HLA-DR2 subtype, and differing for HLA-DM haplotype as well as for the myelin basic protein (MBP) epitope recognized by the vast majority of their T cell lines (TCL) (residues 16-38 and 86-99, respectively). TCL sharing the same restriction element were re-assayed in the presence of reciprocally mismatched antigen-presenting cells (APC). The TCL recognized both the whole MBP and the relevant peptide also in the presence of non-autologous APC, (compatibility for processing, despite a difference in the DM haplotype). The same protocol, performed in serum-free pulsing experiments or in the presence of 'fixed' APC, excluded extracellular processing or mutual T cell presentation, and confirmed the need for MBP processing in our system. The finding, that only TCL recognizing MBP peptide 16-38 (a region not previously related to the DR2 haplotype) used a novel Vbeta, supports the importance of the TCR repertoire over the processing-presentation machinery in the selection of MBP epitopes in MS.

A restricted T cell response to myelin basic protein (MBP) is stable in multiple sclerosis (MS) patients.

The close resemblance of MS to the animal model experimental autoimmune encephalomyelitis (EAE) has provided compelling data sustaining a pathogenic role of circulating T cells reactive against MBP. T cell antigen receptor (TCR) usage in EAE is commonly considered restricted; nevertheless, dynamic changes of TCR usage correlate with the course of EAE, resulting in a limited repertoire during early stages of disease activity followed by the recruitment of other T cells reactive against new determinants. Although a broader TCR repertoire mediates the response to MBP in humans, a restricted intraindividual heterogeneity may occur in some MS patients. In the present study we characterize the response to MBP in MS subjects with relapsing remitting disease from two sampling time points 12 months apart. MBP-specific T cell lines (TCL) were first generated from eight MS individuals and two healthy subjects. New TCL were obtained after 12 months from one control and three MS patients whose response, at the first time point, was directed against a single epitope. Interestingly, these three subjects had a stable and mild disease. Few TCL obtained at two time points from the MS individuals recognized the same immunodominant epitope and shared identical TCR Vbeta sequences. In the control we could not detect a restriction of the repertoire. These findings suggest that in some MS patients with benign disease a predominant T cell response to a single determinant may be detectable at different moments and is mediated by clonally expanded populations.

Characterization of the TCRB chain repertoire in the New World monkey Callithrix jacchus.

Callithrix jacchus is an outbred New World primate characterized by a naturally occurring bone marrow chimerism, restricted polymorphism at many MHC loci, and unusual susceptibility to viral pathogens, adenocarcinoma, colitis, and, following immunization with myelin antigens, a demyelinating disease of the central nervous system closely resembling human multiple sclerosis. Here we characterize the TCRB repertoire in this species, representing the first such analysis in a New World monkey. Two TCRBC, 13 BJ, 2 BD, and 15 BV genes were identified. Overall, a high degree of similarity with human TCRBV-D-J-C gene sequences was observed, indicating a close phylogenetic relationship. Biased usage in favor of genes from the TCRBC1-BJ1 cluster was present in 77% of sequences, in contrast to preferential usage of BC2-BJ2 genes known to occur in humans and mice. Complementarity-determining region 3 averaged 10 amino acids in length and were diverse. Framework regions of TCRBV genes were extensively conserved. Phylogenetic analysis of TCRBV sequences from different species indicated that TCR genes are highly stable across primates. Thus, a diverse TCRB repertoire is generated in C. jacchus despite the limited polymorphism of class I MHC loci. Extensive homology to human TCR genes, natural chimerism, and susceptibility to inflammatory disorders are characteristics of C. jacchus that create a useful model system for the study of human autoimmunity.

T-lymphocytes with gamma delta+ V delta 2+ antigen receptors are present in increased proportions in a fraction of patients with tuberculosis or with sarcoidosis.

T-lymphocytes with T-cell antigen receptor (TCR) comprising a gamma chain and a delta chain (gamma delta+ T cells) are believed to be involved in the immune reaction to mycobacterial antigens, and they have been found in increased proportions in sarcoid patients. We evaluated the proportions of gamma delta+ T-lymphocytes and of two major gamma delta+ subpopulations, the V delta 1+ and the V delta 2+ T-cell subsets, in 10 normal blood donors, in 15 patients with tuberculosis (TB), seven of whom had pleural effusion (PE), and in 12 patients with pulmonary sarcoidosis (PS), nine of whom underwent bronchoalveolar lavage (BAL). T-cell subsets were evaluated in peripheral blood (PBL) of all subjects and in PE from patients with TB and in BAL from patients with PS. Compared with normal blood donors, patients with TB had increased proportions of PBL CD3+ gamma delta+ T cells (6 +/- 1% versus 14 +/- 3% of CD3+ T cells, p < 0.05) because of the presence of four patients who had an increase (respectively, 18.3, 22.0, 24.2, and 35.4% of CD3+ T cells) of gamma delta+ T cells. In patients with TB and PE, gamma delta+ T cells were 7.9 +/- 2.7%, a value not different from that in the tubercular PBL and in normal PBL. Although patients with PS had proportions of PBL gamma delta+ T cells (9.2 +/- 3.4%) similar to those in normal PBL, two patients had increased (35 and 31%) PBL gamma delta+ T-lymphocytes.(ABSTRACT TRUNCATED AT 250 WORDS)