Presence of oligoclonal T cells in cerebrospinal fluid of a child with multiphasic disseminated encephalomyelitis following hepatitis A virus infection

Human abdominal aortic aneurysm (AAA): Evidence for an autoimmune antigen-driven disease

Abdominal aortic aneurism (AAA) is a complex immunological disease with a strong genetic component, and one of the ten leading causes of death of individuals 55-74 years old worldwide. Strong evidence has been accumulated suggesting that AAA is an autoimmune specific antigen-driven disease. Mononuclear cells infiltrating AAA lesions comprised of T and B lymphocytes and other cells expressing early-, intermediate- and late-activation antigens, and the presence of antigen-presenting cells have been documented, demonstrating an ongoing immune response. The three components of the trimolecular complex, T-cell receptor (TCR)/peptide (antigen)/HLA have been identified in AAA, and specifically: (i) clonal expansions of T-cell clones in AAA lesions; (ii) the association of AAA with particular HLA Class I and Class II; and (iii) self or nonself putative AAA-associated antigens. IgG autoantibodies recognizing proteins present in normal aortic tissue have been reported in patients with AAA. Molecular mimicry, defined as the sharing of antigenic epitopes between microorganisms (bacteria, viruses) and self antigens, maybe is responsible for T-cell responses and antibody production in AAA. Also, the frequency and the suppressor activity of CD4 + CD25 + FOXP3+ Tregs and the expression of FOXP3 transcripts and protein have been reported to be significantly impaired in AAA patients vs normal donors.

[Extra hepatic manifestations of hepatitis A]

Viral hepatitis A is characterized by a wide range of clinical pictures ranging from a completely unapparent infection to a fulminant, potentially fatal hepatitis or the classical icteric form. Hepatitis A can develop in an unusual way and extrahepatic manifestations (neurological, renal, haematological, cholecystitis, acute pancreatitis, vasculitis, etc.) can occasionally complicate the course of the disease. Although hepatitis A infection was identified in the early 1970s, there are few or no studies assessing the actual frequency of these complications. They have been studied mainly through clinical case reports. Currently, since the disease has become more common in adults, these complications are being increasingly observed. We present an update on extrahepatic complications during hepatitis A, which should be known by both specialist doctors (infectiologists internists, hepatologists and others) and general practitioners.

Viral Hepatitis and Hepatocellular Carcinoma: State of the Art

Viral hepatitis is one of the main causes leading to hepatocellular carcinoma (HCC). The continued rise in incidence of HCC suggests additional factors following infection may be involved. This review examines recent studies investigating the molecular mechanisms of chronic hepatitis and its association with hepatocarcinogenesis. Hepatitis B virus patients with genotype C display an aggressive disease course leading to HCC more than other genotypes. Furthermore, hepatitis B excretory antigen (HBeAg) seems to be a more sensitive predictive tumor marker exhibiting a six-fold higher relative risk in patients with positive HBsAg and HBeAg than those with HBsAg only. Single or combined mutations of viral genome can predict HCC development in up to 80% of patients. Several mutations in HBx-gene are related with higher HCC incidence. Overexpression of the core protein in HCV leads to hepatocellular lipid accumulation associated with oncogenesis. Reduced number and decreased functionality of natural killer cells in chronic HCV individuals dysregulate their surveillance function in tumor and viral cells resulting in HCC. Furthermore, high T-cell immunoglobulin and mucin 3 levels supress CD8+ T-cells, which lead to immunological dysregulation. Hepatitis D promotes HCC development indirectly via modifications to innate immunity, epigenetic alterations and production of reactive oxygen species with the LHDAg being the most highly associated with HCC development. Summarizing the results, HBV and HCV infection represent the most associated forms of viral hepatitis causing HCC. Further studies are warranted to further improve the prediction of high-risk patients and development of targeted therapeutics preventing the transition from hepatic inflammation–fibrosis to cancer.

Clonally expanded alpha-chain T-cell receptor (TCR) transcripts are present in aneurysmal lesions of patients with Abdominal Aortic Aneurysm (AAA)

Abdominal aortic aneurysm (AAA) is a life-threatening immunological disease responsible for 1 to 2% of all deaths in 65 year old or older individuals. Although mononuclear cell infiltrates have been demonstrated in AAA lesions and autoimmunity may be responsible for the initiation and account for the propagation of the disease, the information available about the pathogenesis of AAA is limited. To examine whether AAA lesions from patients with AAA contain clonally expanded α-chain TCR transcripts, we amplified by the non-palindromic adaptor-PCR (NPA-PCR)/Vα-specific PCR and/or the Vα-specific PCR these α-chain TCR transcripts. The amplified transcripts were cloned and sequenced. Substantial proportions of identical α-chain TCR transcripts were identified in AAA lesions of 4 of 5 patients, demonstrating that clonally expanded T cells are present in these AAA lesions. These results were statistically significant by the bimodal distribution. Three of 5 of these patients were typed by DNA-based HLA-typing and all three expressed DRB1 alleles containing the DRβGln70 amino acid residue that has been demonstrated to be associated with AAA. All three patients exhibited clonally expanded T cells in AAA lesions. Four of the 5 patients with AAA who exhibited clonal expansions of α-chain TCR transcripts, also exhibited clonal expansions of β-chain TCR transcripts in AAA lesions, as we have demonstrated previously (J Immunol 192:4897, 2014). αβ TCR-expressing T cells infiltrating AAA lesions contain T-cell clones which have undergone proliferation and clonal expansion in vivo in response to as yet unidentified specific antigens that may be self or nonself. These results provide additional evidence supporting the hypothesis that AAA is a specific antigen-driven T-cell autoimmune disease.

Escape of pathogens from the host immune response by mutations and mimicry. Possible means to improve vaccine performance

The ability of certain pathogens, such as human immunodeficiency, hepatitis C, herpes simplex, influenza viruses, Plasmodium falciparum, etc., to escape from host immune response is generally ascribed to high mutation rate of their genome. We challenge this assumption and propose that molecular mimicry of host antigens by these pathogens could also participate to this resistance. Several studies show that there is no correlation between the mutation rate value of a pathogen and the possibility to develop an effective vaccine. On the other hand, pathogens which do not respond to vaccine are usually reported to display host protein mimicry. We propose to suppress in the thymus the epitopes of the self which are in common with the pathogen. This could be achieved by intrathymic injection of antibodies against this microorganism. These antibodies would be obtained by vaccination of a foreign animal species. It is expected that the negative selection of the CD4(+) and CD8(+) T lymphocytes specific for these epitopes would be prevented, that the number of epitopes recognized as foreign to the host would be increased and that the immune response diversity would be enhanced.

Aneurysmal lesions of patients with abdominal aortic aneurysm contain clonally expanded T cells

Abdominal aortic aneurysm (AAA) is a common disease with often life-threatening consequences. This vascular disorder is responsible for 1-2% of all deaths in men aged 65 years or older. Autoimmunity may be responsible for the pathogenesis of AAA. Although it is well documented that infiltrating T cells are essentially always present in AAA lesions, little is known about their role in the initiation and/or progression of the disease. To determine whether T cells infiltrating AAA lesions contain clonally expanded populations of T cells, we amplified β-chain TCR transcripts by the nonpalindromic adaptor-PCR/Vβ-specific PCR and/or Vβ-specific PCR, followed by cloning and sequencing. We report in this article that aortic abdominal aneurysmal lesions from 8 of 10 patients with AAA contained oligoclonal populations of T cells. Multiple identical copies of β-chain TCR transcripts were identified in these patients. These clonal expansions are statistically significant. These results demonstrate that αβ TCR(+) T lymphocytes infiltrating aneurysmal lesions of patients with AAA have undergone proliferation and clonal expansion in vivo at the site of the aneurysmal lesion, in response to unidentified self- or nonself Ags. This evidence supports the hypothesis that AAA is a specific Ag-driven T cell disease.

Acute disseminated encephalomyelitis associated with hepatitis A virus infection

We describe the case of a 30-month-old boy who developed acute disseminated encephalomyelitis (ADEM) after hepatitis A virus (HAV) infection and ultimately died. As far as we know, this is only the second case of HAV-associated ADEM to be reported in the literature. The child was brought to hospital with fever, lethargy and weakness of 2 days duration. He had developed jaundice, abdominal pain and malaise 2 weeks beforehand and these problems had resolved within 2 days. Neurological examination revealed lethargy, generalised weakness and positive Babinski's signs bilaterally. Cerebrospinal fluid examination showed mild lymphocytic pleocytosis, increased protein and elevated anti-HAV IgM and IgG titres. Serum HAV IgM and IgG titres were also elevated. Despite aggressive treatment with ceftriaxone, acyclovir and anti-oedema measures, he developed papilloedema and coma within 24 hours of admission. Magnetic resonance imaging of the brain revealed diffuse cerebral oedema and multifocal hyperintensities on T2-weighted images, with most lesions in the white matter of both cerebral hemispheres. The diagnosis of ADEM was established and high-dose steroids and intravenous immunoglobulin were added to the treatment regimen. However, his clinical condition continued to deteriorate and he died on the 20th day in hospital. This case shows that HAV infection can be linked with ADEM. Patients with HAV infection should be examined carefully for central nervous system symptoms during follow-up. Likewise, the possibility of HAV infection should be investigated in cases of ADEM.

Abdominal aortic aneurysm is a specific antigen-driven T cell disease

To determine whether monoclonal/oligoclonal T cells are present in abdominal aortic aneurysm (AAA) lesions, we amplified beta-chain T cell receptor (TCR) transcripts from these lesions by the nonpalindromic adaptor (NPA)-polymerase chain reaction (PCR)/V-beta-specific PCR followed by cloning and sequencing. Sequence analysis revealed the presence of substantial proportions of identical beta-chain TCR transcripts in AAA lesions in 9 of 10 patients examined, strongly suggesting the presence of oligoclonal populations of alphabeta TCR+ T cells. We have also shown the presence of oligoclonal populations of gammadelta TCR+ T cells in AAA lesions. Sequence analysis after appropriate PCR amplification and cloning revealed the presence of substantial proportions of identical VgammaI and VgammaII TCR transcripts in 15 of 15 patients examined, and of Vdelta1 and Vdelta2 TCR transcripts in 12 of 12 patients. These clonal expansions were very strong. All these clonal expansions were statistically significant by the binomial distribution. In other studies, we determined that mononuclear cells infiltrating AAA lesions express early- (CD69), intermediate- (CD25, CD38), and late- (CD45RO, HLA class II) activation antigens. These findings suggest that active ongoing inflammation is present in the aortic wall of patients with AAA. These results demonstrate that oligoclonal alphabeta TCR+ and gammadelta TCR+T cells are present in AAA lesions. These oligoclonal T cells have been clonally expanded in vivo in response to yet unidentified antigens. Although the antigenic specificity of these T cells remains to be determined, these T cells may play a significant role in the initiation and/or the propagation of the AAA. It appears that AAA is a specific antigen-driven T cell disease.

The non-palindromic adaptor-PCR method for the identification of the T-cell receptor genes of an interferon-gamma-secreting T-cell hybridomaspecific for trans-sialidase, an immunodominant Trypanosoma cruzi antigen

Cloning of the T-cell receptor genes is a critical step when generating T-cell receptor transgenic mice. Because T-cell receptor molecules are clonotypical, isolation of their genes requires reverse transcriptase-assisted PCR using primers specific for each different Valpha or Vbeta genes or by the screening of cDNA libraries generated from RNA obtained from each individual T-cell clone. Although feasible, these approaches are laborious and costly. The aim of the present study was to test the application of the non-palindromic adaptor-PCR method as an alternative to isolate the genes encoding the T-cell receptor of an antigen-specific T-cell hybridoma. For this purpose, we established hybridomas specific for trans-sialidase, an immunodominant Trypanosoma cruzi antigen. These T-cell hybridomas were characterized with regard to their ability to secrete interferon-gamma, IL-4, and IL-10 after stimulation with the antigen. A CD3+, CD4+, CD8- interferon-gamma-producing hybridoma was selected for the identification of the variable regions of the T-cell receptor by the non-palindromic adaptor-PCR method. Using this methodology, we were able to rapidly and efficiently determine the variable regions of both T-cell receptor chains. The results obtained by the non-palindromic adaptor-PCR method were confirmed by the isolation and sequencing of the complete cDNA genes and by the recognition with a specific antibody against the T-cell receptor variable beta chain. We conclude that the non-palindromic adaptor-PCR method can be a valuable tool for the identification of the T-cell receptor transcripts of T-cell hybridomas and may facilitate the generation of T-cell receptor transgenic mice.

Oligoclonal T cells are infiltrating the brains of children with AIDS: sequence analysis reveals high proportions of identical beta-chain T-cell receptor transcripts

We have recently described the presence of perivascular CD3+ CD45RO+ T cells infiltrating the brains of children with AIDS. To determine whether these infiltrates contain oligoclonal populations of T cells, we amplified by PCR beta-chain T-cell receptor (TCR) transcripts from autopsy brains of four paediatric patients with AIDS. The amplified transcripts were cloned and sequenced. Sequence analysis of the beta-chain TCR transcripts from all four patients revealed multiple identical copies of TCR beta-chain transcripts, suggesting the presence of oligoclonal populations of T-cells. These TCR transcripts were novel. The presence of oligoclonal populations of T cells in the brains of these four paediatric patients with AIDS suggests that these T cells have undergone antigen-driven proliferation and clonal expansion very likely in situ, in the brains of these AIDS patients, in response to viral or self-antigens. Although the specificity of the clonally expanded beta-chain TCR transcripts remains to be elucidated, none of the beta-chain TCR transcripts identified in this study were identical to those specific for HIV-1 antigens that are currently reported in the GENBANK/EMBL databases. Certain common CDR3 motifs were observed in brain-infiltrating T cells within and between certain patients. Large proportions (24 of 61; 39%) of beta-chain TCR clones from one patient (NP95-73) and 2 of 27 (7%) of another patient (NP95-184-O) exhibited substantial CDR3 homology to myelin basic protein (MBP)-specific TCR derived from normal donors or TCR expressed in the brain of patients with multiple sclerosis (MS) or with viral encephalitis. These two patients (NP95-73 and NP95-184-O) also shared HLA class II with the normal donors and the MS patients who expressed these homologous TCR. Pathologic examination at autopsy of the brains revealed the presence of myelin pallor only in patient NP95-73. T-cell clones identified in the brain of patients NP95-73 and NP95-184-O may recognize MBP or another CNS self antigen and this recognition may be restricted by either DRB1*15 or DQB1*0602 specificities.

Acute disseminated encephalomyelitis in children: discordant neurologic and neuroimaging abnormalities and response to plasmapheresis

OBJECTIVES

To describe our experience with acute disseminated encephalomyelitis (ADEM), focusing on (1) the relationship between clinical course and MRI findings and (2) the response to plasmapheresis in a subgroup of patients.

METHODS

A retrospective record review was conducted of 13 children who were admitted as inpatients with the diagnosis of ADEM during the period 1998-2003.

RESULTS

Diagnosis was established by clinical signs and symptoms, cerebrospinal fluid changes and multifocal involvement of deep gray and white matter based on MRI. Initial therapy was high-dose methylprednisolone and intravenous immunoglobulin in 12 patients. One child improved spontaneously. Six of 12 children did not improve with corticosteroid treatment. All 6 had an acute progressive course neurologically, and 5 of them also showed a delay in the onset of neuroimaging changes, eventually developing lesions in the deep gray matter and brainstem. This latter group received 5 sessions of plasmapheresis and recovered over the course of several months with varying degrees of residual neurologic deficits.

CONCLUSIONS

Presentation of ADEM with delayed development of MRI lesions in deep gray matter and brainstem may herald a prolonged clinical course and lack of response to glucocorticoid therapy. Plasmapheresis might be an effective therapeutic intervention in these patients. The role of plasmapheresis versus corticosteroids and intravenous immunoglobulin as a primary treatment of ADEM needs to be investigated further.

Identification of HLA-DQα and -DRβ Residues Associated With Susceptibility and Protection to Epithelial Ovarian Cancer

Substantial evidence has been accumulated suggesting that T cells in patients with epithelial ovarian carcinoma (EOC) exhibit an antigen-driven immune response directed against the tumor cells. In the context of human leukocyte antigen (HLA), this suggests its possible involvement in the disease. Therefore, we examined the distribution of the HLA-DRB1*, -DQA1*, and -DQB1* alleles in 47 patients with EOC and 67 healthy Caucasian women. The frequency of D(70) and E(71) polymorphic residues of the DRB1 alleles was significantly reduced in EOC patients versus controls (pD(70)E(71) = 0.009), suggesting a protective role against the disease. The DQalpha residues R(52) and Y(11)R(55) were increased in the patients (p = 0.008 and 0.012, respectively). Because residues 11 and 55 participate in the formation of pocket 1, they may be functionally important amino acid positions that influence disease susceptibility. The frequency of the DQalpha susceptibility epitope (R(52)Y(11)R(55)) among the DRbetaD(70)E(71)-positive EOC patients was increased when compared with DRbetaD(70)E(71)-positive controls (EOC, 100%; control, 52%; p = 0.028). Among individuals without the DQalpha susceptibility epitope, the distribution of DRbetaD(70)E(71)-positive cases was significantly different between EOC patients and controls (EOC, 0%; control, 60%; p = 0.039). Therefore, it appears that the presence of DQalpha susceptibility elements overrides the protective effect of the DRbetaD(70)E(71) epitope and suggests an interactive relationship between DRbeta and DQalpha epitopes that may be of importance for disease susceptibility. Because positions DRbeta 70,71 and DQalpha 52 have been implicated in immunologic diseases, it is likely that besides being critical for T-cell recognition, they may also play a role in T-cell development and acquisition of the T-cell repertoire.

Substantial proportions of identical β-chain T-cell receptor transcripts are present in epithelial ovarian carcinoma tumors

To determine whether clonally expanded T cells are present in tumor specimens from patients with epithelial ovarian carcinoma (EOC) we amplified by the non-palindromic adaptor PCR (NPA-PCR) or by Vbeta-specific PCR beta-chain T-cell receptor (TCR) transcripts from these tumor specimens. The amplified transcripts were cloned and sequenced. Sequence analysis revealed the presence of substantial proportions of multiple identical copies of beta-chain TCR transcripts, suggesting the presence of clonal expansions of T cells in these patients, which were statistically significant by the binomial distribution in seven of nine patients. Independent amplification in separate experiments of beta-chain TCR transcripts from one patient by either NPA-PCR or by Vbeta-specific PCR, followed by cloning and sequencing, revealed identical clonal expansions irrespectively of the amplification method used. Multiple identical copies of beta-chain TCR transcripts can be derived only by specific antigen-driven proliferation and clonal expansion of the T-cell clones which recognize these antigens. Because of the very large size of the TCR repertoire, the probability of finding by chance multiple identical copies of these transcripts within an independent sample of T cells is negligible. These results demonstrate that T cells infiltrating solid tumor specimens or malignant ascites of patients with EOC contain monoclonal/oligoclonal populations of T cells.

Molecular epidemiology of hepatitis A in Noord-Brabant, The Netherlands

BACKGROUND

Previous studies on the molecular epidemiology of hepatitis A virus (HAV) in Amsterdam, The Netherlands, show that subgenotype 1A is mainly seen among homosexual men practising anonymous oral-anal sex in saunas and darkrooms, while subgenotype 1B is usually detected among children originating from Morocco, and subgenotype 3A is mostly found among travellers to Pakistan.

OBJECTIVE

We studied the genotype distribution in a more rural area of The Netherlands, Noord-Brabant, and compared it with Amsterdam.

STUDY DESIGN

We collected blood and feces samples from 34 HAV IgM(+) individuals who were reported from August 2001-March 2003 at the Municipal Health Service (MHS) Heart for Brabant (Brabant). We also collected feces samples from nine household contacts of whom the HAV IgM status was not known. HAV RNA was isolated and subsequently amplified by reverse transcriptase polymerase chain reaction (RT-PCR) at the VP1-P2a and the VP3-VP1 region, sequenced and analysed.

RESULTS AND CONCLUSIONS

In most cases, relations between risk groups and HAV subgenotypes in Noord-Brabant were similar to those in Amsterdam. Next to genotypes 1 and 3 we also detected a genotype 2/7 strain in a Noord-Brabant case. Also, in contrast to the Amsterdam study, sporadic transmission occurred among various risk groups. Children involved in a school-related outbreak were infected with strains identical to one that was previously isolated from a man who has sex with men (MSM). Also, Dutch patients having no epidemiological link with Turkish or Moroccan children harboured strains imported from high-endemic countries. Furthermore, we report a special case in which HAV may be causally involved in meningitis. The results of this study show that the molecular epidemiology of HAV in The Netherlands can be more complicated than previously anticipated and that HAV phylogenetic studies can provide important information for the design of appropriate public health measures.

Non-MS recurrent demyelinating diseases

The introduction of MRI has shown that the acute, recurrent (R), and multiphasic (M) forms of disseminated encephalomyelitis (DEM) are more common than suspected in adults, and that their MR images are sufficiently characteristic in most instances to make differentiation from multiple sclerosis (MS) possible. In addition, a number of clinical features of DEM are rarely seen in MS: fever, malaise, nausea, vomiting, positional vertigo, convulsions, aphasia, meningism, bilateral optic neuritis, and CSF leukocytosis and elevated protein. CSF oligoclonal bands are usually absent. It is remarkable that confusion between R- and MDEM and MS persists despite the numerous published reports on recurrent DEM dating back 70 years, many illustrating the characteristic MRIs. There are many case reports of DEM erroneously diagnosed as MS, Schilder's, Marburg's, Devic's, and Baló's disease, and, in particular brain tumors. It is probable that acute DEM is occasionally mistaken for a clinically isolated symptom of MS. Possible mechanisms for recurrence include localization at the site of a previous injury to the nervous system, or by the phenomenon of molecular mimicry. The importance of differentiating R- and MDEM from MS is greater today due to the recommendation that immunodulatory treatment be initiated in patients with a clinically isolated syndrome, or when the occurrence of a second clinical episode establishes the diagnosis of MS.

Theiler's virus infection: a model for multiple sclerosis

Both genetic background and environmental factors, very probably viruses, appear to play a role in the etiology of multiple sclerosis (MS). Lessons from viral experimental models suggest that many different viruses may trigger inflammatory demyelinating diseases resembling MS. Theiler's virus, a picornavirus, induces in susceptible strains of mice early acute disease resembling encephalomyelitis followed by late chronic demyelinating disease, which is one of the best, if not the best, animal model for MS. During early acute disease the virus replicates in gray matter of the central nervous system but is eliminated to very low titers 2 weeks postinfection. Late chronic demyelinating disease becomes clinically apparent approximately 2 weeks later and is characterized by extensive demyelinating lesions and mononuclear cell infiltrates, progressive spinal cord atrophy, and axonal loss. Myelin damage is immunologically mediated, but it is not clear whether it is due to molecular mimicry or epitope spreading. Cytokines, nitric oxide/reactive nitrogen species, and costimulatory molecules are involved in the pathogenesis of both diseases. Close similarities between Theiler's virus-induced demyelinating disease in mice and MS in humans, include the following: major histocompatibility complex-dependent susceptibility; substantial similarities in neuropathology, including axonal damage and remyelination; and paucity of T-cell apoptosis in demyelinating disease. Both diseases are immunologically mediated. These common features emphasize the close similarities of Theiler's virus-induced demyelinating disease in mice and MS in humans.

Acute disseminated encephalomyelitis following hepatitis A virus infection

Acute disseminated encephalomyelitis is an immune-mediated demyelinating disorder usually encountered in children or adolescents and characterized by multifocal neurologic deficits of rapid onset. It is often preceded by various infectious diseases or vaccination, but acute disseminated encephalomyelitis developing after hepatitis A virus infection is rare. We present such a case in a 9-year-old patient who illustrates the importance of considering acute disseminated encephalomyelitis in patients who develop multifocal neurologic signs after hepatitis A virus infection. We suggest that patients with acute disseminated encephalomyelitis be screened for hepatitis A virus because of the occurrence of asymptomatic hepatitis A virus infection.

Identical alpha-chain T-cell receptor transcripts are present on T cells infiltrating coronary arteries of human cardiac allografts with chronic rejection

Chronic cardiac allograft rejection is characterized by graft arteriopathy and is a major obstacle of graft survival. We investigated T-cell receptor (TCR) alpha-chain transcripts of T cells infiltrating human epicardial coronary arteries from cardiac allografts with chronic rejection. The non-palindromic adaptor-polymerase chain reaction (NPA-PCR) was used to specifically amplify TCR alpha-chain transcripts from five explanted cardiac allografts with chronic rejection. The amplified products were cloned and sequenced to obtain the entire ValphaJalpha region. Immuno-histochemistry was used to identify the mononuclear cell infiltrates in the coronary arteries. All the five coronary artery specimens exhibited large populations of infiltrating mononuclear cells, which were primarily comprised of T cells and macrophages. In three specimens, high proportions ( approximately 80%) of identical alpha-chain TCR transcripts were detected. In peripheral blood mononuclear cells from a healthy individual, alpha-chain TCR transcripts were unique when compared to each other. Endomyocardial biopsies collected from one patient six months before the allograft was explanted, contained identical alpha-chain TCR transcripts to those found to be clonally expanded in the coronary arteries from this patient. These results indicate that T cells infiltrating the epicardial arteries of cardiac allografts with chronic rejection undergo proliferation and clonal expansion in response to a specific antigen, which very likely is an (allo)antigen(s).