Analysis of amplified T cell receptor Vβ transcripts by a non-isotopic immunoassay

Expansion of rare CD8+ CD28- CD11b- T cells with impaired effector functions in HIV-1-infected patients

The decline in the number of CD4+ T cells in HIV-1-infected patients is known to be related to the increased number of CD8+CD28- T cells. In this paper, we show that CD8+CD28- T cells from HIV-positive patients have an impaired capability to interact with human endothelial cells. This is due to the dramatic expansion, within this subset, of rare CD11b- cells lacking cell-cell adhesion functions. In 50 HIV-positive patients, 19.5% +/- 6.5% of all T cells were CD8+CD28-CD11b-, whereas only 0.8% +/- 0.4% of all T cells from healthy donors showed this uncommon phenotype. The percentage of circulating CD8+CD28-CD11b- T cells was strongly related to the percentage of CD4+ T cells (r = -0.82). This population is peculiar in terms of HIV infection and was found to possess some characteristics associated with effector functions but its cytotoxic properties were impaired. The percentage of target cells lysed by CD8+CD28-CD11b- was significantly lower than that of cells lysed by its CD11b- counterpart (p <.05) both at low (5:1) or at relatively high (20:1) effector/target ratios. CD8+CD28-CD11b- T cells, which lack the ability to interact with endothelial cells, are likely to accumulate and persist in circulation. The biologic properties of CD8+CD28-CD11b- T cells suggest that these cells might be endstage or aberrant differentiated effector cells. Lack of cell-cell adhesion and impaired cytolytic functions favor the hypothesis of a role for CD8+CD28-CD11b- T cells in the development of immunodeficiency.

Development of autologous T lymphocytes in two males with X-linked severe combined immune deficiency: molecular and cellular characterization

We report on two patients affected with severe combined immune deficiency (SCID) with an unusual immunological phenotype and a substantial number of autologous, poorly functioning T cells. Distinct mutations identified at the IL2RG locus in the two patients impaired IL-2-mediated signaling but affected T-cell lymphopoiesis differently, resulting in generation of a polyclonal or oligoclonal T-cell repertoire. These observations add to the growing complexity of the immunological spectrum of SCID in humans and indicate the need for detailed immunological and molecular investigations in atypical cases.

Intrathymic Restriction and Peripheral Expansion of the T-Cell Repertoire in Omenn Syndrome

Mutations in the human RAG genes that impair, but do not abolish, recombination activity lead to Omenn syndrome, a severe primary immune deficiency that is associated with clinical and pathological features of graft-versus-host disease and oligoclonal expansion of activated, autologous T cells. We have analyzed the mechanisms accounting for peripheral oligoclonality of the T-cell repertoire. Predominance of few T-cell receptor clonotypes (both within TCRAB- and within TCRGD-expressing lymphocytes) is already detectable in the thymus and is further selected for in the periphery, with a different distribution of clonotypes in different tissues. These data indicate that oligoclonality of the T-cell repertoire in Omenn syndrome is due both to intrathymic restriction and to peripheral expansion. Moreover, the RAG genes defect that causes Omenn syndrome directly affects early stages of V(D)J recombination, but does not alter the process of double-strand-break DNA repair, including N and P nucleotide insertion.

T cell receptor BV gene rearrangements in the spinal cords and cerebrospinal fluid of patients with amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a fatal disorder whose etiology and pathogenesis remain unknown. Recent studies, however, have demonstrated the presence of inflammatory infiltrates within ALS spinal cord and suggested the possibility of an immune-mediated process in motor neuron degeneration. We have analyzed the diversity of T-cells in the spinal cord in ALS. Reverse transcriptase polymerase chain reaction (RT-PCR) with variable (V) region sequence specific oligonucleotide primers was used to amplify T-cell receptor (TCR)BV transcripts from spinal cords obtained at autopsy from patients with ALS, patients who died without inflammatory disease of the central nervous system, brains from patients with ALS, and brains from patients who died with inflammatory CNS disease. Sequencing was then performed on the amplified transcripts. An overall increase in the level of TCRBV 2 transcripts was detected in ALS specimens when compared to controls. This result was independent of the HLA genotype of the individual. Furthermore, enrichment of TCRBV2-positive T cells could be demonstrated in cerebrospinal fluid derived from patients with ALS, using PCR analysis and a T cell stimulation assay with toxic shock syndrome toxin-1 (TSST-1), a Vbeta2-specific superantigen. Our results suggest that an immunological process involving the specific expansion of Vbeta2 TCR-positive T-cells may be important in the pathogenesis of ALS.

Identification of overrepresented T cell receptor genes in blood and tissue biopsies by PCR-ELISA

The analysis of T cell receptor variable (TCR V) gene repertoires in blood or tissues may provide important information when studying immunopathological mechanisms. The overexpression of a TCR gene may indicate the expansion of the corresponding T cell subset. In autoimmune diseases, clonally expanded T cell subsets in the affected organs may represent pathogenic lymphocytes. We describe a simple, rapid and sensitive method to determine the TCR AV and BV gene repertoire using a PCR-ELISA method. RNA is extracted from lymphocytes, transcribed to cDNA, which is then used as a template for PCR with 19 different TCR AV gene and 20 BV gene specific primers as the forward primer, and a digoxigenin (DIG) labeled AC/BC primer as the reverse primer. The DIG labeled PCR amplicons are hybridized with a fluorescein isothiocyanate (FITC) labeled TCR C region specific probe. Finally, the amplicons are quantified by ELISA using anti-FITC coated microtiter plates, and an anti-DIG conjugated peroxidase. Although PCR-ELISA cannot accurately quantify the expression level of a given TCR gene, overrepresented TCR V genes are easily identified by comparing the relative expression levels of each individual V gene in the total V gene repertoire. We demonstrate that this technique can be used to determine TCR profiles in blood and tissue samples containing as few as 50,000 T cells. In combination with CDR3 fragment size analysis, this method is an efficient tool to identify clonally expanded T cell subsets in the synovial biopsies of rheumatoid arthritis patients.

Partial V(D)J recombination activity leads to Omenn syndrome

Genomic rearrangement of the antigen receptor loci is initiated by the two lymphoid-specific proteins Rag-1 and Rag-2. Null mutations in either of the two proteins abrogate initiation of V(D)J recombination and cause severe combined immunodeficiency with complete absence of mature B and T lymphocytes. We report here that patients with Omenn syndrome, a severe immunodeficiency characterized by the presence of activated, anergic, oligoclonal T cells, hypereosinophilia, and high IgE levels, bear missense mutations in either the Rag-1 or Rag-2 genes that result in partial activity of the two proteins. Two of the amino acid substitutions map within the Rag-1 homeodomain and decrease DNA binding activity, while three others lower the efficiency of Rag-1/Rag-2 interaction. These findings provide evidence to indicate that the immunodeficiency manifested in patients with Omenn syndrome arises from mutations that decrease the efficiency of V(D)J recombination.

Detection of skewed T-cell receptor V-beta gene usage in the peripheral blood of patients with multiple sclerosis

The ex vivo analysis of the T-cell receptor V-beta (TCRBV) gene usage by circulating T lymphocytes in Multiple Sclerosis (MS) patients may contribute to understanding disease pathogenesis. In the present study, TCRBV gene usage was analyzed in freshly collected unstimulated peripheral blood mononuclear cells (PBMC) isolated from 40 MS patients and 20 healthy controls. Nine patients presented abnormal repertoires, with expansion of one or more TCRBV segments. Among these patients, six presented expansion of TCRBV9 chain expression, three also having an expansion of TCRBV1, TCRBV11 and TCRBV22 segments. The most frequently observed TCRBV chain expansion, TCRBV9, was further analyzed and identified as polyclonal. Evaluation of clinical variables showed that median disease duration was shorter in patients with TCRBV gene expression abnormalities. Longitudinal evaluation of five patients with a skewed repertoire showed regression of expanded TCRBV chains expression to normal values. These data indicate that certain MS patients have abnormal TCRBV gene expression. Such abnormalities are caused by polyclonal expansions of T lymphocyte subpopulations that use the same TCRBV gene families, are unstable and preferentially observed early in the course of the disease.

Development of Autologous, Oligoclonal, Poorly Functioning T Lymphocytes in a Patient With Autosomal Recessive Severe Combined Immunodeficiency Caused by Defects of the Jak3 Tyrosine Kinase

Defects of the common gamma chain subunit of the cytokine receptors (γc) or of Jak3, a tyrosine kinase required for γc signal transduction, result in T−B+ severe combined immunodeficiency (SCID). However, atypical cases, characterized by progressive development of T lymphocytes, have been also reported. We describe a child with SCID caused by Jak3 gene defects, which strongly but not completely affect Jak3 protein expression and function, who developed a substantial number (>3,000/μL) of autologous CD3+CD4+ T cells. These cells showed a primed/activated phenotype (CD45R0+ Fas+HLA-DR+ CD62Llo), defective secretion of T-helper 1 and T-helper 2 cytokines, reduced proliferation to mitogens, and a high in vitro susceptibility to spontaneous (caused by downregulation of bcl-2 expression) as well as activation-induced cell death. A restricted T-cell receptor repertoire was observed, with oligoclonal expansion within each of the dominant segments. These features resemble those observed in γc-/y and in Jak3−/−mice, in which a population of activated, anergic T cells (predominantly CD4+) also develops with age. These results suggest that residual Jak3 expression and function or other Jak3-independent signals may also permit the generation of CD4+ T cells that undergo in vivo clonal expansion in humans; however, these mechanisms do not allow development of CD8+ T cells, nor do they fully restore the functional properties of CD4+ T lymphocytes.

Development of Autologous, Oligoclonal, Poorly Functioning T Lymphocytes in a Patient With Autosomal Recessive Severe Combined Immunodeficiency Caused by Defects of the Jak3 Tyrosine Kinase

Defects of the common gamma chain subunit of the cytokine receptors (γc) or of Jak3, a tyrosine kinase required for γc signal transduction, result in T−B+ severe combined immunodeficiency (SCID). However, atypical cases, characterized by progressive development of T lymphocytes, have been also reported. We describe a child with SCID caused by Jak3 gene defects, which strongly but not completely affect Jak3 protein expression and function, who developed a substantial number (>3,000/μL) of autologous CD3+CD4+ T cells. These cells showed a primed/activated phenotype (CD45R0+ Fas+HLA-DR+ CD62Llo), defective secretion of T-helper 1 and T-helper 2 cytokines, reduced proliferation to mitogens, and a high in vitro susceptibility to spontaneous (caused by downregulation of bcl-2 expression) as well as activation-induced cell death. A restricted T-cell receptor repertoire was observed, with oligoclonal expansion within each of the dominant segments. These features resemble those observed in γc-/y and in Jak3−/−mice, in which a population of activated, anergic T cells (predominantly CD4+) also develops with age. These results suggest that residual Jak3 expression and function or other Jak3-independent signals may also permit the generation of CD4+ T cells that undergo in vivo clonal expansion in humans; however, these mechanisms do not allow development of CD8+ T cells, nor do they fully restore the functional properties of CD4+ T lymphocytes.

Oligoclonal CD4+CD57+ T-Cell Expansions Contribute to the Imbalanced T-Cell Receptor Repertoire of Rheumatoid Arthritis Patients

A peculiar feature of rheumatoid arthritis patients is that they carry clonally expanded CD4+ and CD8+ cells in the peripheral blood. While the distortion of the repertoire of CD8+ cells has been ascribed to the increase of CD8+CD57+ large granular lymphocytes, often detected in these patients, the mechanism responsible for the clonal expansion of CD4+ cells remains unexplained. Here, we report that CD4+CD57+ cells, that in healthy individuals represent a small subset of peripheral CD4+ lymphocytes, are significantly expanded in the peripheral blood of a considerable percentage of rheumatoid arthritis patients. Furthermore, the expansion of these lymphocytes appears to correlate with the presence of rheumatoid factor. The molecular analysis of the T-cell receptor variable beta segments expressed by the CD4+CD57+ cells enriched in rheumatoid arthritis patients showed that they use restricted repertoires, that partially overlap with those of their CD4−CD57+ counterpart. The structural feature of the receptor ligand expressed by these cells revealed that their expansion is most likely mediated by strong antigenic pressures. However, since we also found that CD4+CD57+ and CD4−CD57+ cells can share the same clonal specificity, it is likely that their selection is not mediated by conventional major histocompatibility complex restricted mechanisms. Thus, while our data demonstrate that CD4+CD57+ cells play an important role in establishing the imbalance of the CD4+ cell repertoire observed in rheumatoid arthritis patients, they also suggest that these cells have common features with mouse CD4+CD8−NK1.1+/T cells.

Missense Mutations in the Fas Gene Resulting in Autoimmune Lymphoproliferative Syndrome: A Molecular and Immunological Analysis

Programmed cell death (or apoptosis) is a physiological process essential to the normal development and homeostatic maintenance of the immune system. The Fas/Apo-1 receptor plays a crucial role in the regulation of apoptosis, as demonstrated by lymphoproliferation in MRL-lpr/lpr mice and by the recently described autoimmune lymphoproliferative syndrome (ALPS) in humans, both of which are due to mutations in the Fas gene. We describe a novel family with ALPS in which three affected siblings carry two distinct missense mutations on both the Fas gene alleles and show lack of Fas-induced apoptosis. The children share common clinical features including splenomegaly and lymphadenopathy, but only one developed severe autoimmune manifestations. In all three siblings, we demonstrated the presence of anergic CD3+CD4−CD8− (double negative, [DN]) T cells; moreover, a chronic lymphocyte activation was found, as demonstrated by the presence of high levels of HLA-DR expression on peripheral CD3+ cells and by the presence of high levels of serum activation markers such as soluble interleukin-2 receptor (sIL-2R) and soluble CD30 (sCD30).

Detection of hepatitis B virus DNA in chronic carriers of hepatitis B surface antigen in southwestern Greece

The presence of hepatitis B virus (HBV) DNA in sera of 56 chronic carriers of hepatitis B surface antigen (HBsAg) was determined by three methods: the Abbott hybridization assay, the polymerase chain reaction (PCR) followed by gel electrophoresis and UV visualization (PCR-GE), and PCR followed by DNA enzyme immunoassay (PCR-DEIA). HBV DNA was detected in four samples positive for hepatitis Be antigen (HBeAg) by all methods used. Both PCR-GE and PCR-DEIA detected viraemia in two anti-HBe, anti-HBc IgM positive samples. In the group of 50 anti-HBe positive samples the sensitivity of the three methods was 10%, 24% and 32%, respectively. PCR-GE and PCR-DEIA results correlated well with the patients' clinical status; of 20 patients with elevated ALT levels, 12 (60%) were found to be positive in the PCR-GE and another 2 were found to be positive in the PCR-DEIA (70%). These data indicate that PCR-DEIA is the most sensitive method for detection of HBV DNA. This method can be relatively easily applied in the clinical laboratory for monitoring the progression of disease and/or interferon therapy in patients with chronic hepatitis B.

Insertion of a short human immunodeficiency virus (HIV)-2 gp36 sequence into an HIV-1 p24 recombinant protein results in a polypeptide with potent and TCRBV-restricted T cell triggering activity

In the present work we investigate whether artificial alterations of the structure of an inactive retrovirus-encoded protein could transform it in a superantigen. As a model system we used a recombinant human immunodeficiency virus (HIV)-1 p24 protein and two of its variants in which a short peptide corresponding to sequences of gp41 of HIV-1 (HIV-1 p24*) or gp36 of HIV-2 (HIV-1-2 p24*) has been inserted nearby the carboxy-terminal end of HIV-1 p24. As expected both HIV-1 p24 and HIV-1 p24* were inactive, while HIV-1-2 p24* was a potent inducer of human, but not murine, T cell proliferation. The possibility that the observed activity was due to contaminants was ruled out since the proliferative response could be specifically inhibited by a monoclonal anti-p24 antibody and by a peptide encompassing the area of HIV-1 p24/HIV-2 gp36 junction. Furthermore, the data exclude the possibility that the gp36 insertion is per se responsible for the observed proliferative activity. The analysis of the functional, phenotypic and molecular properties of the responding cells demonstrated that the response was class II dependent and that the activated cells were predominantly CD4+CD8- expressing a strongly biased repertoire of TCRBV segments. Collectively, these data strongly suggest that the HIV-1-2 p24* fusion protein shares common functional properties typical of superantigen molecules. Thus, our demonstration that a viral protein can be transformed into a superantigen simply by the insertion of a short peptide at the carboxy-terminal end has important implications for understanding the mode of action of retrovirus-encoded superantigens.

Analysis of the V beta specificity of superantigen activation with a rapid and sensitive method using RT PCR and an automatic DNA analyser

Polymerase chain reaction (PCR) by the specific amplification of a DNA target sequence has been shown to permit analysis of T cell receptor usage. The complete repertoire is amplified using oligonucleotide primers specific for each of the known V alpha or V beta regions of the T cell receptor. One of the methods currently used to appreciate the relative quantity of different V chains of the TCR is by coamplifying in the same reaction tube the variable region of one chain together with the constant region of the other chain. We have optimised PCR conditions and analysed PCR products on an automatic DNA analyser facilitating the quantification of the amplified products, avoiding the use of radioisotopes, and allowing the determination of the sizes of CDR3 regions, thus giving new information on the modification of the T cell repertoire. This method was used to analyse the precise V beta specificity of the T cell activation with the superantigen SEB.

The expressed T cell receptor V gene repertoire of rheumatoid arthritis monozygotic twins: rapid analysis by anchored polymerase chain reaction and enzyme-linked immunosorbent assay

Because of heterogeneity in the outbred human population, it has been difficult to determine the genetic factors that influence the expressed T cell receptor (TcR) repertoire in autoimmune diseases. To overcome this problem, we have developed a combination of anchored polymerase chain reaction (APCR) and enzyme-linked immunosorbent assay (ELISA) that can accurately assess TcR V gene frequencies in numerous clinical samples. The results are independent of amplification efficiency, and V gene usage can be readily analyzed with an ELISA plate reader and associated software. Using this method, the TcR V beta gene repertoires in peripheral lymphocytes from nine sets of identical twins, normal, concordant or discordant for rheumatoid arthritis (RA), were studied. The TcR V beta results were compared with TcR V gamma frequencies in the same specimens as determined by APCR-ELISA and cDNA sequence analysis. The results showed a marked similarity in the TcR V beta gene repertoires between identical twins, compared to unrelated subjects (p < 0.05) whether or not they were concordant or discordant for RA. In contrast, the TcR V gamma gene repertoires in the monozygotic twins differed as much as in controls. The data imply that (a) the human TcR V beta gene repertoire in peripheral blood is genetically controlled, whereas (b) the TcR V gamma gene repertoire is primarily influenced by environmental stimuli, and (c) RA causes no consistent change in TcR V beta repertoire of peripheral blood. The APCR-ELISA method, in the context of large-scale family and population studies, should facilitate a more precise delineation of the genetic factors that regulate human TcR V beta expression.

T cell repertoire and autoimmune diseases

Self-reactivity and autoimmunity are processes related to the breakage of self-tolerance that can be distinguished by their different clinical outcome and are widely accepted cornerstones of immunology. The finding that several potentially autoaggressive cells contribute to the repertoire of healthy individuals has stimulated a great deal of experimental work aimed at understanding the mechanisms that prevent autoimmune pathology. In this review we will consider the basic principles, and our present knowledge of the rules that preside over the interplay of the immune system with self-components. One viewpoint stresses the importance of major histocompatibility complex (MHC) and non-MHC genes in determining genetic predisposition to develop autoimmune phenomena. At a different level there is a strong interest in understanding the mechanisms of processing and presentation of self antigens, especially during ontogeny. Another topic of major interest concerns the interaction between MHC genes and the T cell receptor (TcR) complex as well as the identification of TcR V genes that are preferentially expressed by autoimmune T cells. All of these aspects are evaluated in the context of tolerance based on deletion and anergy. Finally we will propose a general model of autoimmunity based on the most recent findings concerning the biological activity of exogenous superantigens.