T-cell Receptor Gene Rearrangement Patterns Research Articles

Nævus géant congénital

A hallmark of lymphoid malignancies is the presence of a monoclonal lymphocyte population. Monoclonality of B- and T-cell populations can be established through immunoglobulin (IG) or T-cell receptor (TCR) gene rearrangement analysis, respectively. The biological rationale of IG and TCR gene rearrangement analysis is that due to the extensive combinatorial repertoire made possible by V(D)J recombination in lymphocytes, it is unlikely that any substantive lymphocyte population would share the same IG or TCR gene rearrangement pattern unless there is an underlying neoplastic or reactive origin. Modern IG and TCR gene rearrangement analysis is typically performed by polymerase chain reaction (PCR) using commercially available primer sets followed by gel capillary electrophoresis. This process is highly sensitive in the detection of nearly all lymphoid malignancies. Several pitfalls and limitations, both biological and technical, apply to IG/TCR gene rearrangement analysis, but these can be minimised with high quality controls, performance of assays in duplicate, and adherence to strict criteria for interpreting and reporting results. Next generation sequencing (NGS) will likely replace PCR based methods of IG/TCR gene rearrangement analysis but is not yet widespread due to the absence of standardised protocols and multicentre validation.

A case of T cell prolymphocytic leukemia involving blast transformation

We report a case of T cell prolymphocytic leukemia (T-PLL) involving blast transformation. At the initial diagnosis, most peripheral blood cells demonstrated proliferation of indolent T cell small cell variants, i.e., small to medium prolymphocytes with inconspicuous nucleoli and a normal karyotype. These cells were positive for surface CD4, CD5, and CD7, and cytoplasmic CD3, but negative for surface CD3 and CD8 and cytoplasmic terminal deoxynucleotidyl transferase (TdT). The T cell receptor (TCR) Cβ1 gene was rearranged in the cells. Large prolymphocytes with prominent nucleoli, irregular nuclei, and cytoplasmic vacuoles that exhibited chromosome 8 trisomy were observed about 1.5 years later. The CD4+CD8- single positive effector memory T cells transformed into surface CD4+CD8+ double positive precursor T cells. The clonal TCR gene rearrangement patterns of these cells were identical throughout the clinical course, suggesting clonal blast transformation. The CD4+CD8+ cells demonstrated increased chromosome 8 trisomy combined with complex chromosome abnormalities with t(14;14)(q11.2;q32) containing a 14q32 chromosome after transformation. T cell leukemia 1a (TCL1a) (14q32.1) may be implicated in this case. The TCL1a oncoprotein is expressed in approximately 70% of T-PLL cases. The disease gradually developed resistance to chemotherapy, and the patient died of the disease. It is known that indolent T-PLL can become aggressive. Therefore, similar transformations may occur in other aggressive T-PLL cases, particularly those involving trisomy 8 and TCL1a.

Pediatric histiocytic sarcoma clonally related to precursor B‐cell acute lymphoblastic leukemia with homozygous deletion of CDKN2A encoding p16INK4A

Histiocytic sarcoma (HS) is a rare malignancy of tissue histiocytes with a dismal prognosis. We report a 4-year-old male who developed HS during maintenance chemotherapy for precursor B-cell acute lymphoblastic leukemia (pre-B ALL). Both tumors showed identical clonal immunoglobulin and T-cell receptor gene re-arrangement patterns, as well as homozygous deletion of the CDKN2A gene encoding p16(INK4A). These data suggest a clonal relationship between the two neoplasms despite their distinct lineages. Since CDKN2A deletion predisposes to development of HS in experimental models, the cytogenetic features of the patient's pre-B ALL may have predisposed to this change in lineage.

Mepolizumab as a corticosteroid-sparing agent in lymphocytic variant hypereosinophilic syndrome

Mepolizumab, a monoclonal anti-IL-5 antibody, is an effective corticosteroid-sparing agent for patients with Fip1-like 1/platelet-derived growth factor receptor α fusion (F/P)-negative hypereosinophilic syndrome (HES). Lymphocytic variant hypereosinophilic syndrome (L-HES) is characterized by marked overproduction of IL-5 by dysregulated T cells. To determine whether patients with L-HES respond to mepolizumab in terms of corticosteroid tapering and eosinophil depletion to the same extent as corticosteroid-responsive F/P-negative patients with HES and a normal T-cell profile. Patients enrolled in the mepolizumab trial were evaluated for L-HES on the basis of T-cell phenotyping and T-cell receptor gene rearrangement patterns, and their serum thymus-and-activation-regulated chemokine (TARC) levels were measured. Response to treatment was compared in patient subgroups based on results of these analyses. Lymphocytic variant HES was diagnosed in 13 of 63 patients with HES with complete T-cell assessments. The ability to taper corticosteroids on mepolizumab was similar in patients with L-HES and those with a normal T-cell profile, although a lower proportion of patients with L-HES maintained eosinophil levels below 600/μL. Increased serum TARC levels (>1000 pg/mL) had no significant impact on the ability to reduce corticosteroid doses, but a lower proportion of patients with elevated TARC achieved eosinophil control on mepolizumab. Mepolizumab is an effective corticosteroid-sparing agent for patients with L-HES. In some cases however, eosinophil levels remain above 600/μL, suggesting incomplete neutralization of overproduced IL-5 or involvement of other eosinophilopoietic factors.

In vivo mutant frequency of thioguanine-resistant T-cells in the peripheral blood and lymph nodes of melanoma patients

T-cell activation by malignant melanoma would be anticipated to stimulate T-cell proliferation, which in turn has been associated with increasing the likelihood of somatic gene mutation. The purpose of this study was to test the hypothesis that in vivo hypoxanthine guanine phosphoribosyltransferase ( hprt ) mutant frequencies (MFs) are increased in peripheral blood T-cells from melanoma patients compared to normal controls. Assays were made of 48 peripheral blood samples from melanoma patients with stage 3 (13 patients) and stage 4 (35 patients) disease, 38 normal controls, and of nine tumor bearing lymph nodes. The mean hprt log 10(MF) in patient peripheral blood was −4.77 (geometric mean hprt MF=17.0×10 −6) compared to a mean hprt log 10(MF) of −4.87 (geometric mean hprt MF=13.5×10 −6) in controls. Although modest, this difference is statistically significant both by t-test ( P=0.049) and after adjustment for covariates of age, gender, and cigarette smoking by regression analysis ( P=0.001). Among the melanoma patients, the mean log 10(MF) for the 17 patients who had received potentially genotoxic therapies was not significantly different from the mean log 10(MF) for the 31 patients not receiving such therapies. The hprt MFs in the nine tumor bearing nodes were compared with MFs in peripheral blood from the same patients and revealed a non-significant ( P=0.07) trend for increasing MFs in blood. Furthermore, analyses of T-cell receptor gene rearrangement patterns revealed hprt mutants originating from the same in vivo clone in both peripheral blood and a tumor-bearing node. The finding of elevated hprt MFs not entirely explained by genotoxic therapies in patients compared to controls can be explained either by hypermutability or in vivo T-cell activation. The similar MFs in peripheral blood and tumor bearing lymph nodes, as well as the finding of mutant representatives of the same in vivo T-cell clone in both locations, support monitoring peripheral blood to detect events in the nodes. If in vivo proliferation accounts for the current findings, the hprt deficient ( hprt−) mutant fraction in blood may be enriched for T-cells that mediate the host immune response against malignant melanoma. Further studies will characterize the functional reactivity of hprt mutant isolates against melanoma-related antigens.

Intensified therapy for infants with acute lymphoblastic leukemia

We read with great interest the report by Silverman et al.1 summarizing treatment outcome in 23 infants treated with Dana-Farber Cancer Institute Consortium protocols. Intensified multidrug therapy resulted in significantly improved long term, event free survival in 54% ± 11% of infants. This included at least three patients with MLL gene rearrangements, which are known to be associated with multidrug-resistant disease. The authors describe two infants in whom the blasts at the time of recurrence differed phenotypically from those at diagnosis. They considered the possibility of secondary leukemia, but also speculated about recurrence of the leukemia with a phenotypic shift. In our opinion, the latter explanation appears most probable. In acute lymphoblastic leukemia (ALL) occurring in infants, particularly in cases with MLL gene rearrangements, leukemogenesis affects early progenitor cells. In such patients cross-lineage expression of myeloid antigens such as CD13, CD15, CD33, and CD65 frequently is observed,2 in a minority of cases even biphenotypic acute leukemia has been diagnosed based on simultaneous expression of lineage specific antigens.3 Using clone specific markers such as clonal immunoglobulin (Ig) and T-cell receptor (TCR) gene rearrangements, it is possible to distinguish between recurrence and secondary, therapy-related leukemia. We previously described a pre-B-ALL patient who developed acute myeloid leukemia 17 months after diagnosis, suggesting the development of secondary leukemia. However, the Ig and TCR gene rearrangement pattern was identical between diagnosis and recurrence, implying cytomorphologic and immunophenotypic evolution of the same clone.4 In contrast to previous reports,3 Silverman et al.1 clearly showed that infant ALL in principle can be cured. However, 50% of patients still recur. This implies that analysis of specimens at diagnosis is not sufficient for predicting treatment response and that more insight is needed into in vivo effectiveness of treatment during the follow-up. This is possible with the currently available standardized techniques for the detection of minimal residual disease (MRD).5 To exemplify this strategy we show the monitoring of MRD in a 10-month-old infant with common ALL using a patient specific oligonucleotide probe to the junctional region of an IGK gene rearrangement (Fig. 1 (178k)).6 Despite cytomorphologic remission at the end of induction therapy, we still could detect low levels of malignant cells. The recurrence 14 months after diagnosis was predicted 3 months earlier with molecular MRD analysis. We believe that such prospective MRD monitoring can be used for the assessment of treatment response and can be applied toward individualization of therapy to improve the outcome of infant leukemia further. VκVII and Kde primers were used for polymerase chain reaction (PCR) amplification of bone marrow DNA samples at diagnosis (D) as well as during follow-up. The PCR products were spotted onto a nylon membrane, which was hybridized with the 32P-labeled junctional region probe. Tenfold dilution series of diagnosis DNA revealed a sensitivity of 10-4 (one acute lymphoblastic leukemia cell between 104 normal cells). During follow-up the bone marrow became negative after Week 15, but at Week 47 PCR positivity was found again (i.e., 3 months before clinical recurrence [R]). bp: base pairs; MNC: DNA from normal mononuclear cells. Tomasz Szczepański M.D.*

Analysis of Ig and T-Cell Receptor Genes in 40 Childhood Acute Lymphoblastic Leukemias at Diagnosis and Subsequent Relapse: Implications for the Detection of Minimal Residual Disease by Polymerase Chain Reaction Analysis

AbstractThe rearrangement patterns of Ig and T-cell receptor (TcR) genes were studied by Southern blot analysis in 30 precursor B-cell acute lymphoblastic leukemias (B-ALLs) and 10 T-ALLs at diagnosis and subsequent relapse. Eight precursor B-ALLs appeared to contain biclonal/oligoclonal Ig heavy-chain (IgH) gene rearrangements at diagnosis. Differences in rearrangement patterns between diagnosis and relapse were found in 67% (20 cases) of precursor B-ALLs (including all eight biclonal/oligoclonal cases) and 50% (five cases) of T-ALLs. In precursor B-ALLs, especially changes in IgH and/or TcR-δ gene rearrangements were found (17 cases), but also changes in TcR-β, TcR-γ, Igκ, and/or Igλ genes (11 cases) occurred. The changes in T-ALLs concerned the TcR-β, TcR-γ, TcR-δ, and/or IgH genes. Two precursor B-ALLs showed completely different Ig and TcR gene rearrangement patterns at relapse, suggesting the absence of a clonal relation between the leukemic cells at diagnosis and relapse and the development of a secondary leukemia. The clonal evolution in the other 23 ALL patients was based on continuing rearrangement processes and selection of subclones. The development of changes in Ig and TcR gene rearrangement patterns was related to remission duration, suggesting an increasing chance of continuing rearrangement processes with time. These immunogenotypic changes at relapse occurred in a hierarchical order, with changes in IgH and TcR-δ genes occurring after only 6 months of remission duration, whereas changes in other Ig and TcR genes were generally detectable after 1 to 2 years of remission duration. The heterogeneity reported here in Ig and/or TcR gene rearrangement patterns at diagnosis and relapse might hamper polymerase chain reaction (PCR)-mediated detection of minimal residual disease (MRD) using junctional regions of rearranged Ig or TcR genes as PCR targets. However, our data also indicate that in 75% to 90% of ALLs, at least one major rearranged IgH, TcR-γ, or TcR-δ band (allele) remained stable at relapse. We conclude that two or more junctional regions of different genes (IgH, TcR-γ, and/or TcR-δ) should be monitored during follow-up of ALL patients for MRD detection by use of PCR techniques. Especially in biclonal/oligoclonal precursor B-ALL cases, the monitoring should not be restricted to rearranged IgH genes, but TcR-γ and/or TcR-δ genes should be monitored as well, because of the extensive changes in IgH gene rearrangement patterns in this ALL subgroup.

Analysis of Ig and T-cell receptor genes in 40 childhood acute lymphoblastic leukemias at diagnosis and subsequent relapse: implications for the detection of minimal residual disease by polymerase chain reaction analysis

The rearrangement patterns of Ig and T-cell receptor (TcR) genes were studied by Southern blot analysis in 30 precursor B-cell acute lymphoblastic leukemias (B-ALLs) and 10 T-ALLs at diagnosis and subsequent relapse. Eight precursor B-ALLs appeared to contain biclonal/oligoclonal Ig heavy-chain (IgH) gene rearrangements at diagnosis. Differences in rearrangement patterns between diagnosis and relapse were found in 67% (20 cases) of precursor B-ALLs (including all eight biclonal/oligoclonal cases) and 50% (five cases) of T-ALLs. In precursor B-ALLs, especially changes in IgH and/or TcR-delta gene rearrangements were found (17 cases), but also changes in TcR-beta, TcR- gamma, Ig kappa, and/or Ig lambda genes (11 cases) occurred. The changes in T-ALLs concerned the TcR-beta, TcR-gamma, TcR-delta, and/or IgH genes. Two precursor B-ALLs showed completely different Ig and TcR gene rearrangement patterns at relapse, suggesting the absence of a clonal relation between the leukemic cells at diagnosis and relapse and the development of a secondary leukemia. The clonal evolution in the other 23 ALL patients was based on continuing rearrangement processes and selection of subclones. The development of changes in Ig and TcR gene rearrangement patterns was related to remission duration, suggesting an increasing chance of continuing rearrangement processes with time. These immunogenotypic changes at relapse occurred in a hierarchical order, with changes in IgH and TcR-delta genes occurring after only 6 months of remission duration, whereas changes in other Ig and TcR genes were generally detectable after 1 to 2 years of remission duration. The heterogeneity reported here in Ig and/or TcR gene rearrangement patterns at diagnosis and relapse might hamper polymerase chain reaction (PCR)-mediated detection of minimal residual disease (MRD) using junctional regions of rearranged Ig or TcR genes as PCR targets. However, our data also indicate that in 75% to 90% of ALLs, at least one major rearranged IgH, TcR-gamma, or TcR-delta band (allele) remained stable at relapse. We conclude that two or more junctional regions of different genes (IgH, TcR-gamma, and/or TcR-delta) should be monitored during follow-up of ALL patients for MRD detection by use of PCR techniques. Especially in biclonal/oligoclonal precursor B-ALL cases, the monitoring should not be restricted to rearranged IgH genes, but TcR-gamma and/or TcR-delta genes should be monitored as well, because of the extensive changes in IgH gene rearrangement patterns in this ALL subgroup.

In vivo ionizing irradiations produce deletions in the hprt gene of human T-lymphocytes

The hprt T-lymphocyte cloning assay, which detects mutations occurring in vivo in humans, has been used to examine mutants induced in patients receiving radioimmunoglobulin therapy (RIT) for cancer. Samples from 13 patients before treatment (controls) and 15 samples from 12 patients after treatment were studied for both mutant frequencies and molecular changes in the hprt mutant T-cell clones. Patients were studied up to 48 months after treatment. Post-RIT patients showed increased mutant frequencies as compared to pre-treatment values. T-cell receptor (TCR) gene analysis of mutant T-cell clones demonstrated that 84% arose independently, both pre- and post-treatment, which is the same proportion as seen in normal individuals. However, several individuals did show large sets of mutants with the same TCR gene rearrangement patterns. Molecular analysis of mutants demonstrated a greater proportion of mutations with hprt gene changes on Southern blots after RIT treatment than before (40% versus 20%). RIT increases the proportion of mutations with total rather than partial gene deletions or other gross structural changes compared to normal individuals or pre-treatment patients. These studies are defining the spectrum for radiation-induced hprt gene mutations in vivo in human T-lymphocytes.

Human autologous tumor-specific T cells in malignant melanoma

T cell lines and clones with autologous tumor-specific activity have been developed in malignant melanoma by stimulating peripheral blood lymphocytes (PBL), lymph node lymphocytes or tumor-infiltrating lymphocytes (TIL) with autologous melanoma cells in the presence of recombinant interleukin 2 (rIL2). T-cell lines and clones have been developed with specific cytotoxicity and/or proliferative responses for autologous melanoma targets but not for allogeneic melanoma tumor cells, autologous normal cells or natural killer (NK)-sensitive targets. The concentration of rIL2 is critical for the generation of autologous tumor-specific T-cell lines, with low rIL2 concentrations (up to 800 IU/ml) facilitating the growth of T-cell lines with tumor-specific activity. The alpha beta T-cell receptor (TCR) and the CD3 antigen are involved in specific cytotoxicity and/or proliferative responses of these T-cell lines and clones. An oligoclonal pattern of beta-chain TCR gene rearrangements was observed on T-cell lines and clones with autologous tumor-specific cytotoxicity, suggesting that they are comprised of T cells that have undergone a clonal expansion in response to particular antigen. Autologous tumor-specific cytotoxic T cells are HLA-restricted and recognize on the melanoma tumor cells HLA Class I or possibly Class II antigens plus a tumor-specific determinant. TIL from patients with metastatic melanoma have unique characteristics in comparison with PBL and lymph node lymphocytes and they appear to contain substantial proportions of T cells that have been locally sensitized to autologous tumor cells. Single stimulation of TIL with autologous tumor cells in the presence of rIL2 is sufficient for the generation of T cell lines with autologous tumor-specific activity, whereas, multiple stimulation of PBL and lymph node lymphocytes was required to achieve the same purpose. TIL-derived T cell lines have been expanded in rIL2 in vitro by at least 1,500-fold without losing their activity. Approximately, 40% of the patients exhibited complete or partial responses to adoptive immunotherapy with melanoma TIL and rIL2.

Diversity of rheumatoid synovial tissue T cells by T cell receptor analysis. Oligoclonal expansion in interleukin‐2–responsive cells

The synovitis of rheumatoid arthritis (RA) is characterized by infiltrates of CD4+ T lymphocytes. To determine the clonal diversity of these cells, we cloned T cells with interleukin-2 (IL-2), alone or with phytohemagglutinin (PHA), directly from actively inflamed synovial tissue obtained at synovectomy. A total of 205 clones from 4 specimens was analyzed for T cell receptor (TCR) gene rearrangements using Hind III and Eco RI digests with beta chain and gamma chain complementary DNA probes. A comparison of the TCR rearrangements enabled us to determine if the T cell clones arose from the same or different precursor cells. Most of the T cell clones (92%) had distinct TCR gene rearrangement patterns, indicating a unique clonal origin. However, a few clones (1 quadruplicate and 6 pairs) with identical TCR rearrangements were identified, and these clonal multiples were most commonly found in clones selected with IL-2 alone. Mass cultures were propagated with IL-2, alone or with PHA, and at each passage, cells were removed for TCR analysis. The later passages of the lines selected with IL-2 had oligoclonal TCR rearrangements, whereas no oligoclonal rearrangements were found in the PHA + IL-2-selected cell lines. The TCR rearrangements in the later passages of the IL-2 mass cultures were often identical to the TCR rearrangements that were found in the IL-2-derived clonal multiples. These findings indicate that while the majority of CD4+ T cells within the actively inflamed rheumatoid joint have diverse clonal origins, small numbers of clonal multiples and oligoclonal populations are present, and these cells may be enriched in an IL-2-responsive T cell subset.

Genotypic analyses of richter's syndrome

The authors report the immunogenotype of two cases of Richter's syndrome. The immunoglobulin gene rearrangement pattern obtained on Southern Blot analysis was found in both cases to be the same in leukemic blood cells and in the tissue involved by the lymphoma. The beta chain and gamma chain T-cell receptor gene rearrangement pattern exhibited a germ-line configuration in the peripheral blood cells and in the lymph node in Case 2, whereas in Case 1 the lymph node had a gene rearrangement in the beta chain, as well as in the gamma chain T-cell receptor, and the leukemic cells from bone marrow were found to be in a germ-line configuration for T-cell receptors (beta and gamma chains).

Rearrangement of Immunoglobulin and T Cell Receptor Genes in Acute and Chronic Leukaemias

The pattern of immunoglobulin (Ig) and T cell receptor (TCR) gene rearrangements was determined in 87 patients with acute and chronic leukaemias and myelodysplastic syndromes by Southern blot hybridisation. All 31 cases of common, B cell and null cell acute lymphoblastic leukaemia, and B cell chronic lymphocytic leukaemia showed Ig heavy chain (JH) rearrangement, and TCR (beta-chain) rearrangement was seen in all 5 cases of T cell acute lymphoblastic leukaemia. Inappropriate JH and TCR (beta) rearrangements were present in some cases of T-ALL (60%) and common acute lymphoblastic leukaemia (18%), respectively. For the 19 patients with acute leukaemias following chronic myeloid leukaemia, blastic transformation, all 4 with lymphoid transformation and 3 of the 15 with myeloid transformation had JH rearrangement, and 3 CD10-positive lymphoid transformation and 2 myeloid transformation had their TCR (beta) genes rearranged. In conclusion, the pattern of Ig and TCR gene rearrangements correlated well with the cell lineage. However, cross-lineage rearrangements were more commonly seen in patients with acute leukaemias following chronic myeloid leukaemia blastic transformation, as compared to the de novo cases.

Clonal analysis of T cell infiltrates in synovial tissue of patients with rheumatoid arthritis

To investigate the possibility of the presence of disease-relevant, antigen-specific immune reactions in rheumatoid arthritis (RA), clonal diversity of the T cells in the synovial tissue was examined. T cells were directly cloned by in vitro stimulation with phytohemagglutin and interleukin 2 from both the peripheral blood and inflammatory synovial tissue. Their clonotypes were defined by analyzing rearrangement patterns of T cell receptor (TCR) β and γ chain genes using Southern blotting. In total, 111 clones from the synovial tissue (four patients) and 45 from the peripheral blood (one patient) were studied. Although most of the clones were unique in their TCR gene rearrangement patterns, 2 clones from the synovial tissue of one patient had identical patterns. These 2 clones were CD3+, 4−, 8+. Since phenotypic analysis of 82 clones from the synovial tissues revealed that CD8+ T cell clones were less frequent (24%) than CD4+ clones, the clonal identity observed here in 2 clones may not be negligible. Furthermore, 1 CD8+ clone from the peripheral blood of the same patient also had the same clonotype. These results may suggest selective trafficking or proliferation of CD4−, CD8+ T cells in RA synovial tissue.

Rearrangement of immunoglobulin, T-cell receptor, and bcl-2 genes in malignant lymphomas in Hong Kong

The pattern of malignant lymphomas in the Hong Kong Chinese population is characterized by a low incidence of Hodgkin's disease and follicular lymphomas. The authors studied the immunoglobulin (Ig), T-cell receptor (TCR), and bcl-2 gene rearrangement in 62 cases of malignant lymphoma in this population by Southern blot hybridization. Two cases of Hodgkin's disease showed no rearrangement of the Ig and TCR genes. All 42 cases of B-cell lymphoma had Ig heavy chain (JH) rearrangement with or without additional rearrangement of the light chains (C kappa and C lambda). One case of diffuse B-cell lymphoma had additional T-cell receptor beta-chain (C beta) rearrangement. Sixteen of 18 cases of T-cell lymphoma had C beta rearrangement, and one case of T-lymphoblastic lymphoma had additional JH rearrangement. Two of eight (25%) cases of follicular lymphoma but only one of the 34 (2.9%) cases of diffuse B-cell lymphoma had bcl-2 rearrangement that was detected by pFL-1 probe. None of the 62 cases showed bcl-2 rearrangement using the pFL-2 probe. In conclusion, the Ig and TCR gene rearrangement pattern of the lymphomas found in Hong Kong correlates well with the T-cell and B-cell lineage, which is similar to reports in the white population. However, the incidence of bcl-2 gene rearrangement in follicular B-cell lymphoma is lower than that reported in the US but comparable with that in Japan.

Molecular analyses of in vivo hprt mutations in human T-lymphocytes III. Longitudinal study of hprt gene structural alterations and T-cell clonal origins

The hprt clonal assay detects mutations occurring in vivo in the hypoxanthine-guanine phosphpribosyltransferase ( hprt) gene of human T-lymphocytes. Analysis of 94 wild-type and 326 hprt mutant clones from 3 normal males was performed using Southern blotting with hprt and T-cell receptor (TCR) gene probes. Gross structural alterations of the hprt gene occurred in ∼ 14% of the in vivo derived mutants. Breakpoints were randomly distributed across the gene with one possible mutational “hot spot” observed. Most hprt mutants were independent as judge by TCR gene rearrangement patterns indicating that the measured hprt mutant frequency is a good measure of the actual hprt mutation frequency. However, sibling mutants (generally doublets and triplets except for one nonamer) were detected. Information on the timing in vivo of the hprt mutational events and the persistence in vivo of sibling mutants was also obtained.

Histogenesis of Hodgkin's disease: Possible insights from a comparison with lymphomatoid papulosis

Comparison of LyP and HD suggests that these are closely related lymphoproliferative disorders that may occur in the same patient, share similar histologic features, and have the same immunologic phenotype. Recent studies of the molecular biology of both disorders confirm a similar distribution of T-cell receptor gene rearrangement patterns. The study of LyP, although a rare and benign disorder, has improved our understanding of HD, which appears, in some cases, to be a proliferation of malignant activated T lymphocytes. Further analysis of LyP may lead to a better understanding of the spontaneous regression of this disorder and result in new methods for treatment of HD.