Telomere length changes in patients with aplastic anaemia

To investigate telomere changes in patients with aplastic anaemia (AA) and clinical factors influencing the telomere dynamics, telomere length (TL) was measured in peripheral blood mononuclear cells using Southern blot analysis of 42 patients with AA and 39 healthy normal controls. Nineteen patients received supportive treatment only, while the remaining 23 patients received immunosuppressive therapy with anti-thymocyte globulin or anti-lymphocyte globulin +/- cyclosporin A. In AA patients, TL was on average 1.41 kb shorter than that of age-matched normal controls (P < 0.001). In patients treated with immunosuppression, the mean TL of non-responders was significantly shorter than that of age-matched normal controls (P < 0.001), while no difference in TL was detected in responders compared with controls. Positive correlation was observed between the extent of telomere shortening, the severity of neutropenia (P = 0.05) and the degree of mean corpuscular volume elevation (P = 0.005) at the time of the study. However, there was no correlation with time elapsed since diagnosis (P = 0.214). These findings suggest that haematopoietic stem cells in patients with AA rapidly lose TL at the onset of the disease. The TL shortening may reflect the severity of impairment of haematopoiesis.     

Analysis of telomere length in mantle cell lymphoma

Mantle cell lymphoma (MCL) is a well defined lymphoid neoplasm genetically characterized by the t(11;14)(q13;q32). Telomeres play an essential role in preserving chromosomal integrity and genomic stability; their shortening can lead to telomere dysfunction and chromosomal instability, a critical factor in cancer development. In this study, telomere length (TL) measured by terminal restriction fragments (TRF) assay in DNA samples of tumor cells from 20 patients with MCL was evaluated. Results were correlated with clinical, morphologic and cytogenetic characteristics. In all cases, the presence of the CCND1/IGH@ rearrangement was confirmed by fluorescence in situ hybridization and/or PCR analysis. TL in total MCL patients revealed a mean TRF value (4.51 ± 0.79 kb) significantly shorter than those observed in controls (7.49 ± 1.94 kb) (P < 0.001); 30% of patients had TL shorter than 4.0 kb. TRF length was not associated with patients age (P = 0.07; r = 0.17) nor with sex (females: 4.33 ± 0.51 kb and males: 4.57 ± 0.85 kb; P = 0.63). No significant differences were found between patients studied at diagnosis (13) (4.44 ± 0.81 kb) respect to those analyzed at relapse (7) (4.63 ± 0.82 kb) (P = 0.53). In addition, we compared patients with (4.84 ± 1.09 kb) and without (4.40 ± 0.68 kb) complex karyotypes (P = 0.45) and cases with typical morphology (4.48 ± 0.79 kb) vs. blastoid variant (4.63 ± 1.04 kb) (P = 0.83), and no significant differences between them were found. Although the number of cases of our series is not large, our results showed that TL reduction in MCL is independent of the clinical characteristics, morphology and karyotype.     

Telomere shortening in the colonic mucosa of patients with ulcerative colitis

Telomere length in human somatic cells gradually decreases with the number of cell divisions and is regarded as a marker of somatic cell turnover. Mucosal cells of the affected colon show rapid turnover in individuals with active ulcerative colitis (UC). Telomere length was determined by Southern blot analysis of terminal restriction fragments (TRFs) from the colonic mucosa of 17 patients with UC in remission, two of whom showed dysplasia, and 17 control subjects without colitis. For each individual, mean TRF length was compared between rectal mucosa and unaffected cecal mucosa. The mean TRF length of the rectal mucosa was significantly less than that of cecal mucosa in UC patients (7.87 ± 0.36 kb versus 8.77 ± 0.21 kb; P = 0.0015, Wilcoxon signed rank test), whereas no significant difference was detected in the control subjects. The extent of telomere shortening was 10.6 ± 3.35% in UC patients, compared with 0.8 ± 0.64% in noncolitis controls (P = 0.0024, Mann-Whitney U-test). Four UC patients, two of whom had dysplasia, showed telomere shortening of more than 20% in the rectal mucosa. These observations suggest that telomere shortening in the colonic mucosa of individuals with UC may represent the history of mucosal inflammation during disease of long duration, and that it may contribute to aneuploidy in UC. (Received May 6, 1997; accepted Sept. 26, 1997)     

Telomere shortening occurs in Asian Indian Type 2 diabetic patients.

AIM: Telomere shortening has been reported in several diseases including atherosclerosis and Type 1 diabetes. Asian Indians have an increased predilection for Type 2 diabetes and premature coronary artery disease. The aim of this study was to determine whether telomeric shortening occurs in Asian Indian Type 2 diabetic patients. METHODS: Using Southern-blot analysis we determined mean terminal restriction fragment (TRF) length, a measure of average telomere size, in leucocyte DNA. Type 2 diabetic patients without any diabetes-related complications (n = 40) and age- and sex-matched control non-diabetic subjects (n = 40) were selected from the Chennai Urban Rural Epidemiology Study (CURES). Plasma level of malondialdehyde (MDA), a marker of lipid peroxidation, was measured by TBARS (thiobarbituric acid reactive substances) using a fluorescence method. RESULTS: Mean (+/- SE) TRF lengths of the Type 2 diabetic patients (6.01 +/- 0.2 kb) were significantly shorter than those of the control subjects (9.11 +/- 0.6 kb) (P = 0.0001). Among the biochemical parameters, only levels of TBARS showed a negative correlation with shortened telomeres in the diabetic subjects (r = -0.36; P = 0.02). However, telomere lengths were negatively correlated with insulin resistance (HOMA-IR) (r = -0.4; P = 0.01) and age (r = -0.3; P = 0.058) and positively correlated with HDL levels (r = 0.4; P = 0.01) in the control subjects. Multiple linear regression (MLR) analysis revealed diabetes to be significantly (P < 0.0001) associated with shortening of TRF lengths. CONCLUSIONS: Telomere shortening occurs in Asian Indian Type 2 diabetic patients.     

Telomere length study in celiac disease

OBJECTIVES: Telomeres are important structures that are critical for maintaining chromosomal integrity and cell surveillance. The aim of this study was to analyze telomere length in patients with celiac disease (CD), a multifactorial disorder with a strong genetic component that exhibits genomic instability and cancer predisposition, particularly T-cell lymphomas. METHODS: Telomere length measured by telomere restriction fragments (TRF) was studied in small intestinal biopsy (SIB) samples and peripheral blood lymphocytes (PBL) from 20 untreated CD patients, distributed according to the clinical form as four asymptomatic, five monosymptomatic, and 11 polysymptomatic individuals. We also analyzed TRF from normal peripheral blood lymphocytes and normal biopsy samples as normal controls. RESULTS: TRF evaluation showed a significant telomere shortening in SIB samples from CD patients (4.21 +/- 0.29 Kb) compared to PBL from the same individuals (9.17 +/- 0.35 Kb) (p < 0.0001), independently of clinical form. Mean TRF peak values from normal biopsy samples were significantly higher (8.33 +/- 0.38 Kb) than those observed in CD biopsy samples (p < 0.001). No differences between TRF values in CD-PBL and normal peripheral blood lymphocytes (8.89 +/- 0.37Kb) were found. CONCLUSIONS: Our findings in patients with CD, a disorder in which the gluten-induced mucosal injury could accelerate telomere shortening, would increase the process of end-to-end fusions resulting in chromosomal changes, supports the hypothesis that genomic instability and telomere reduction may play a role in the cancer predisposition observed in these patients.     

Accelerated telomere shortening and telomerase activation in Fanconi's anaemia

Fanconi's anaemia (FA) is an autosomal recessive disorder characterized by progressive bone marrow failure that often evolves towards acute leukaemia. FA also belongs to a group of chromosome instability diseases. Because telomeres are directly involved in chromosomal stability and in cell proliferation capacity, we examined telomere metabolism in peripheral blood mononuclear cells (PBMC). Telomere length was significantly shorter in 54 FA patient samples, compared to 51 controls (P<0.0001). In addition, mean telomere terminal restriction fragment lengths (TRF) in nine heterozygous patient samples did not differ from those of controls. In 14 samples from FA patients with severe aplastic anaemia (SFA), telomere length was significantly shorter than in 22 samples of age-matched FA patients with moderate haematological abnormalities (NSFA) (P<0.001). However, no correlation was found between TRF length and the presence of bone marrow clonal abnormalities in 16 additional, separately analysed, patient samples. Sequential measurement of TRF in six FA patients showed an accelerated rate of telomere shortening. Accordingly, telomere shortening rate was inversely correlated with clinical status. Telomerase, the enzyme that counteracts telomere shortening, was 4.8-fold more active in 25 FA patients than in 15 age-matched healthy controls. A model for the FA disease process is proposed.     

The distribution and accumulation of the shortest telomeres in telomere biology disorders

Individuals with telomere biology disorders (TBDs) have very short telomeres, high risk of bone marrow failure (BMF), and reduced survival. Using data from TBD patients, a mean leukocyte Southern blot telomere length (TL) of 5 kilobases (kb) was estimated as the ‘telomere brink’ at which human survival is markedly reduced. However, the shortest telomere, not the mean TL, signals replicative senescence. We used the Telomere Shortest Length Assay (TeSLA) to tally TL of all 46 chromosomes in blood-derived DNA and examined its relationship with TBDs. Patients (n = 18) had much shorter mean TL (TeSmTL) (2.54 ± 0.41 kb vs. 4.48 ± 0.52 kb, p < 0.0001) and more telomeres <3 kb than controls (n = 22) (70.43 ± 8.76% vs. 33.05 ± 6.93%, p < 0.0001). The proportion of ultrashort telomeres (<1.6 kb) was also higher in patients than controls (39.29 ± 10.69% vs. 10.40 ± 4.09%, p < 0.0001). TeS <1.6 kb was associated with severe (n = 11) compared with non-severe (n = 7) BMF (p = 0.027). Patients with multi-organ manifestations (n = 10) had more telomeres <1.6 kb than those with one affected organ system (n = 8) (p = 0.029). Findings suggest that TBD clinical manifestations are associated with a disproportionately higher number of haematopoietic cell telomeres reaching a telomere brink, whose length at the single telomere level is yet to be determined.     

Telomere shortening in leucocyte subsets of long-term survivors of allogeneic bone marrow transplantation

Recent studies have demonstrated excessive telomeric shortening in peripheral blood leucocytes of bone marrow transplant (BMT) recipients. This finding has raised concerns about accelerated haemopoietic ageing that might predispose to clonal disorders and late graft failure. We studied the peripheral blood neutrophils and T cells of 14 fully engrafted long-term survivors of BMT.
We found that in both neutrophils and T cells there was significant telomere shortening in the recipient (0.6 and 0.5 kb, respectively; P  < 0.001 and < 0.04, respectively). We found no relationship between degree of shortening and the nucleated cell dose given at the time of transplant. We also demonstrated significantly longer telomeres in T cells than neutrophils from the same individual (mean 11.6 kb and 10.6 kb, respectively; P =0.0001).
We propose mechanisms to account for these observations. The replicative stress that causes this telomere shortening does not necessarily occur at the level of the most primitive haemopoietic stem cell.     

Accelerated telomere shortening following allogeneic transplantation is independent of the cell source and occurs within the first year post transplant

Telomere shortening has been documented in the blood cells of recipients of allogeneic bone marrow transplants compared with their donors. Allogeneic peripheral blood progenitor cells (PBPCs) have been increasingly used as an alternative to bone marrow. Their advantages include earlier engraftment and immune reconstitution following transplantation. We have measured telomere length of neutrophils and T cells in fully engrafted recipients of allogeneic bone marrow (n = 19) and allogeneic PBPC (n = 17) and also measured sequential telomere length in four patients after transplantation. Overall, significant telomere shortening occurred in recipients in neutrophils (0.3 kb, P < 0.001) and T cells (0.2 kb, P = 0.045). The data demonstrate that first, the degree of shortening was the same for BM and PBPC transplants and was not related to the time taken to engraft neutrophils and platelets and second, telomere shortening occurs in the first year post transplant without further shortening during the period of observation. These data suggest that the superiority of engraftment seen in PBPC transplants is independent of telomere shortening and other mechanisms such as homing or seeding may be more important.     

Establishment of Novel Human Esophageal Cancer Cell Line in Relation to Telomere Dynamics and Telomerase Activity

The telomere and the telomerase in human esophageal cancer are not yet completely understood. The regulatory mechanism of telomerase activity and telomere dynamics has drawn considerable attention. It is generally assumed that when telomerase has been activated, no further telomere shortening should ensue; however, a much more complex pattern of telomere dynamics may exist in telomerase-positive cancer cells. A novel human esophageal cancer cell line (KAN-ES) was established and characterized. Using KAN-ES and its serially passaged subclones up to the 55th generation, we determined the alteration of telomere length (TRF), telomerase activity (TA), telomerase RNA expression (hTR), population doubling time, karyotype, and cytokeratin 14 expression during the process of establishing a cancer cell line. We found that the TRF was maintained between 4.0 and 5.0 kb during the serial passages, despite sustained high TA (assessed by an in vitro TRAP assay). No close relationships were found among TRF, TA, and hTR expression. TA and telomere dynamics were not associated with cellular growth ability and differentiation. However, the number of population doublings showed significant correlations with both the TA and doubling times. In conclusion, these dissociations between telomere dynamics and TA support the existence of additional controls on TRF in cancer cells. KAN-ES and its restored subclones should prove a valuable resourse for esophageal cancer research.     

An analysis of telomere length in sarcoidosis

We investigated telomere (terminal restriction fragment [TRF]) length in 111 patients with sarcoidosis regarding both the mean TRF length and the telomere length distribution. A significant decrease was observed in the mean TRF length in sarcoidosis patients in comparison to the age-matched controls, whereas a decreased telomere length was only associated with age in men. The mean TRF shortening seemed to be accelerated in men in their 30s and 50s and in women in their 40s and 50s. We also found a significant decrease with age of telomeres with lengths of 9.4-6.6 kb in men and women in their 20s and an increase of telomeres with lengths of 4.4-2.3 kb in men and women in their 20s and in men in their 50s in sarcoidosis patients versus in the controls who were in their 20s and 50s. These findings suggest the occurrence of age-advanced changes in telomere length in patients with sarcoidosis, regardless of the patient age at the onset of sarcoidosis.     

The natural history of telomeres: tools for aging animals and exploring the aging process

We have been exploring the use of telomere length as a technique to age animals. If telomere restriction fragments (TRFs) shorten predictably with age in a particular tissue, then measurement of TRFs will allow estimation of ages of animals when age cannot be measured directly. This would be particularly useful in population studies where tissue samples can be collected, but age of individuals or age structure of the population is otherwise unknown. We have demonstrated that rate of change in length of TRFs from blood cells can be used to estimate age in a number of avian species. Calibration of this telomere 'clock' using known-age individuals has led to new questions regarding the importance of TRF shortening in aging and its evolution in animals with differing life spans. Our current data show a tight correlation between telomere rate of change (TROC) and maximum life span in birds, with the longest living species having the slowest TROC. In contrast, absolute length of TRFs is not correlated with maximum life span. Very long-lived Leach's storm-petrels have telomeres that in fact lengthen with age! These data suggest that in the longest-lived organisms, cellular replicative life span may not be constrained by shortening telomeres. Published data show that TRFs shorten more slowly in long-lived mammals than in short-lived ones, although for birds and mammals of similar life span, telomere shortening is faster in mammals than in birds. This corresponds with the relatively greater longevity in birds than in mammals.     

Long-term lymphoma survivors following high-dose chemotherapy and autograft: evidence of permanent telomere shortening in myeloid cells, associated with marked reduction of bone marrow hematopoietic stem cell reservoir

OBJECTIVE: To investigate telomere length (TL) and hematopoietic progenitors in long-term survivors after high-dose chemotherapy and peripheral blood stem cell (PBSC) autograft. METHODS: Peripheral blood (PB) and bone marrow (BM) samples were obtained from 31 subjects in continuous complete remission from a high-risk lymphoma, at a median of 5.8 years (range: 1-11 years) since autograft. Most of them were grafted with large PBSC quantities (median CD34(+ve) cells/kg: 7 x 10(6)). TL was determined by Southern blot analysis, BM progenitors by in vitro long-term culture-initiating cells (LTC-IC) and colony assays. RESULTS: TL of PB granulocytes was significantly shortened in autografted subjects compared with age-matched healthy subjects; a similar finding was observed in BM. The median TL reduction in granulocytes from autografted subjects compared with age-matched controls (Delta(TelShortening)) was then assessed according to time interval since autograft. Three subject subgroups were identified-at 1 to <3 years, 3 to <6 years, and 6 to 11 years since autograft-and their telomere loss was the same, with Delta(TelShortening) of 1132, 1379, and 1214 bp in the three subgroups, respectively. The longitudinal assessment of TL in five representative patients followed for up to 40 months since autograft confirmed that telomere shortening occurring during exposure to chemotherapy as well as postautograft is persistent at long term. BM LTC-IC and multipotent and committed progenitors were assessed in subjects at >3 years after autograft and found to be markedly reduced compared with normal controls. CONCLUSION: High-dose chemotherapy and PBSC autograft may result in myelopoietic cell abnormalities that appear to be irreversible.     

Activated idiotype-reactive cells in suppressor/cytotoxic subpopulations of monoclonal gammopathies: correlation with diagnosis and disease status

The phenotypic pattern of peripheral blood T (PBT) lymphocytes was correlated with diagnosis and clinical status in 63 patients with monoclonal gammopathies (MGs). The numbers of lymphocytes expressing activation and CD11 determinants were significantly increased in suppressor/cytotoxic and helper/inducer subpopulations of patients with multiple myeloma (MM) and MG of undetermined significance (MGUS). The number of activated suppressor/cytotoxic cells was closely correlated with diagnosis and disease status. These cells were significantly higher in MM at diagnosis (160 +/- 88) than MGUS patients (61 +/- 79; P less than .01). Their number decreased to MGUS levels in MM in stable remission (58 +/- 53), but not in MM with tumor progression (172 +/- 102; P less than .001). In individual patients, part of these cells specifically adhered to dishes precoated with the related M-protein. No monoclonal T-beta gene rearrangement was detected in PBT and cytotoxic/suppressor subpopulations from two patients with a large proportion of activated cells.     

Multiple myeloma with deletion of chromosome 13q is characterized by increased bone marrow neovascularization

Anti-angiogenesis therapy with thalidomide has been reported to have marked activity in multiple myeloma (MM). As cytogenetics is an independent prognostic factor in MM, we analysed bone marrow (BM) angiogenesis and cytogenetic abnormalities in 34 patients with active MM. BM microvessel density (MVD), as determined by staining with anti-CD34, was significantly higher in MM (MVD: 221 +/- 94 per mm2) than in controls (80 +/- 36; P < 0.0001). In patients with the presence of at least one unfavourable cytogenetic abnormality (deletion of 13q14, deletion of 17p13, aberrations of 11q), a significantly increased BM MVD was observed (254 +/- 93 vs. 160 +/- 60 in patients with absence of these abnormalities; P = 0.0035). Further analyses indicated that increased BM MVD was significantly correlated with deletion of 13q14 (259 +/- 96 vs. 188 +/- 80; P = 0. 026), but not with other cytogenetic, clinical and laboratory MM parameters. We conclude that BM neovascularization is particularly high in MM with deletion of 13q14, which provides a rationale for use of anti-angiogenic strategies in the treatment of MM with high-risk cytogenetics.     

Significant increase of CKS1B amplification from monoclonal gammopathy of undetermined significance to multiple myeloma and plasma cell leukaemia as demonstrated by interphase fluorescence in situ hybridisation

The genetic events that lead to tumour progression in plasma cell dyscrasia are not well understood. Interphase cytoplasmic fluorescence in situ hybridisation was used to investigate the CKS1B amplification status (at 1q21) in clonal plasma cells from 123 patients: 23 monoclonal gammopathy of undetermined significance (MGUS), 75 multiple myeloma (MM) and 26 plasma cell leukaemia (PCL). While CKS1B amplification was absent in MGUS patients, such amplification (3-8 copies) was detected in 36% of newly diagnosed MM, 52% relapsed MM and 62% PCL (P < 0.001). Our results suggest that CKS1B amplification is associated with transformation from MGUS to MM and progression to PCL.     

High frequencies of chromosomal aberrations in multiple myeloma and monoclonal gammopathy of undetermined significance in direct chromosome preparation

Although many cases of multiple myeloma (MM) and monoclonal gammopathy of undetermined significance (MGUS) are cytogenetically normal, interphase fluorescence in situ hybridization (FISH) analyses reveal aberrations in the majority of the cases. Most likely, non-neoplastic cells are more prone to divide in culture than neoplastic cells. Direct chromosome preparations (DCP) would be one way to circumvent this methodological problem. We have investigated 47 bone marrow samples from 39 patients by DCP. A median of 58 metaphases (range 9-158) was analysed per sample. Interphase FISH analyses using probes to detect IGH rearrangements, -13/13q-, +3, +7, and +11 were also performed. Abnormal karyotypes were detected in 15 (63%) of 24 MM and in 4 (50%) of eight MGUS/smouldering MM (SMM) cases that could be successfully cytogenetically analysed. Age, sex, or degree of bone marrow plasma cell (PC) infiltration did not influence the karyotypic patterns (P > 0.05). However, the frequencies of aberrant karyotypes varied in relation to the Colcemide concentrations used - 7% (30 ng/ml) versus 69% and 67% (100 and 200 ng/ml, respectively) (P = 0.01). Combining the G-banding and FISH results, abnormalities were detected in 29 of 31 (94%) MM and in six of eight (75%) MGUS/SMM patients. Thus, cytogenetic and FISH analyses after DCP using 100-200 ng Colcemide/ml identified aberrations in most MM/MGUS/SMM, irrespective of PC percentages.     

Dynamics of telomere shortening in neutrophils and T lymphocytes during ageing and the relationship to skewed X chromosome inactivation patterns

Human haemopoiesis undergoes profound changes throughout life, resulting in compromised regenerative capacity of haemopoietic stem cells. It has been suggested that telomere shortening results in senescence of haemopoietic stem cell subsets and may influence the balance between stem cell renewal and proliferation. Telomere length and telomerase activity was measured in whole blood leucocytes, neutrophils and T cells from cord blood and individuals aged from 1 year to 96 years. Rapid telomere shortening [700 base pairs (bp)] was demonstrated in the first year of life, followed by a gradual decline of 31 bp/year. T cells were shown to have longer telomeres than neutrophils (mean difference 372 bp, P = < 0.001) but demonstrated similar rates of shortening (20 +/- 0.3 bp/year vs. 22 +/- 0.3 bp/year). Telomerase was detectable in T cells but not in neutrophils, suggesting that telomerase is not the rate-limiting step for regulation of telomere length in haemopoietic cells. Stem cell utilization as measured by X chromosome inactivation patterns was found to be independent of telomere length. This supports the concept that age-dependent skewed haemopoiesis is the result of random stem cell loss or X-allelic exclusion rather than telomeric senescence. These studies provide insight into the ageing process and a reference point for evaluating replicative stress in individuals of different age groups.     

Expression profile of shelterin components in plasma cell disorders. Clinical significance of POT1 overexpression

The core complex of telomere-associated proteins, named the shelterin complex, plays a critical role in telomere protection and telomere length (TL) homeostasis. In this study, we have explored changes in the expression of telomere-associated genes POT1, TIN2, RAP1 and TPP1, in patients with monoclonal gammopathy of undetermined significance (MGUS) and multiple myeloma (MM). A total of 154 patients: 70 with MGUS and 84 with MM were studied. Real-time quantitative PCR was used to quantify gene expression. TL was evaluated by Terminal Restriction Fragments. Our data showed increased expression of POT1, TPP1, TIN2 and RAP1 in MM with respect to MGUS patients, with significant differences for POT1 gene (p = 0.002). In MM, the correlation of gene expression profiles with clinical characteristics highlighted POT1 for its significant association with advanced clinical stages, high calcium and β2-microglobulin levels (p = 0.02) and bone lesions (p = 0.009). In multivariate analysis, POT1 expression (p = 0.04) was a significant independent prognostic factor for overall survival as well as the staging system (ISS) (p < 0.02). Our findings suggest for the first time the participation of POT1 in the transformation process from MGUS to MM, and provide evidence of this gene as a useful prognostic factor in MM as well as a possible molecular target to design new therapeutic strategies.     

Human myeloma: several subsets of circulating lymphocytes express plasma cell-associated antigens

Peripheral blood lymphocytes from 9 monoclonal gammopathies of undetermined significance (MGUS) and 27 multiple myelomas (MM) were studied with a panel of monoclonal antibodies (MoAb) that recognize B and T lymphocytes and plasma cells. No difference in the percentage of B lymphocytes, identified by B1 and B4 MoAb, was observed in MGUS and MM patients versus normal controls. However, high percentages of circulating lymphocytes expressing plasma cell-associated antigens were detected in MM (HAN-PC1+ = 29.4 +/- 20.4%; TEC-T10+ = 27.8 +/- 19.2%) whereas they were in the normal range in MGUS (HAN-PC1+ = 8.8 +/- 5.8% p = 0.006; TEC-T10+ = 5.7 +/- 4.7% p less than 0.001). Almost identical results were obtained using PCA-1 MoAb in 17 of these patients. TEC-T10+ and PCA-1+ lymphocytes were sorted and re-analyzed with phycoerythrin conjugated MoAb in 3 healthy subjects, 2 MGUS, and 4 MM patients. In normal subjects and in MGUS the majority of PCA-1+ cells belonged to the B lineage (Leu 2-, Leu3-, Leu 15-, HLA-Dr+), whereas the majority of TEC-T10+ cells are represented by activated T cells and NK cells (Leu 15+). In MM an abnormal expansion of T lymphocytes was chiefly responsible for the high values of lymphocytes expressing plasma cell-associated antigens. Moreover, in MM a clinical evaluation showed a correlation between the presence of these lymphocytes and an aggressive disease. Indeed, they can be considered a useful prognostic marker.