Clonal T Cells in the Blood of Patients With Systemic Sclerosis FREE

In a prospective study, French et al¹ found that clonal T cells are frequently detected in peripheral blood samples from patients with systemic sclerosis (SSc). In their series, expanded clonal T cells were found in 6 (46%) of 13 peripheral blood samples from patients with SSc, whereas no clonal T cells were found in the control group.¹ The authors suggested that clonal T cells may play a critical role in the pathogenesis of SSc.¹ These data prompted us to conduct a prospective study (1) to evaluate the prevalence of a T-cell clonal population in peripheral blood samples from patients with SSc and (2) to determine a possible relationship between both clinical and biological parameters of patients with SSc and the presence of a T-cell clonal population in peripheral blood samples.

Blood samples were obtained from all patients, and peripheral blood mononuclear cells were immediately isolated from whole blood using the Ficoll-Hypaque technique.¹ Analysis of T-cell receptor γ gene rearrangement using polymerase chain reaction and denaturating gradient gel electrophoresis (TCR-γ PCR DGGE) was performed as previously described.²

Thirty-eight consecutive patients with a definite diagnosis of SSc were included in the study. The criteria for the diagnosis of SSc were based on the American College of Rheumatology criteria.³ All patients were seen at the University of Rouen Medical Center, Rouen, France, between 2001 and 2002. There were 6 men and 32 women, with a median age of 54 years (age range, 26-87 years); the median duration of the disease, considered to have existed from the onset of the Raynaud phenomenon, was 55 months (range, 8-432 months). Patients were classified according to the criteria of Leroy et al³ : 10 patients (26%) had diffuse cutaneous SSc (dcSSc) and 28 (74%) had limited cutaneous SSc (lcSSc).

The findings of TCR-γ PCR DGGE of the blood samples from patients with SSc were compared with those from 76 age- and sex-matched healthy subjects (12 men and 64 women; median age, 57 years; age range, 29-89 years). For each patient, we attempted to select 2 same-sex control subjects whose age was within 5 years of the patient’s age. None of the patients with SSc or the control subjects had a history of other connective tissue disorders or hematologic diseases (eg, lymphoma, cutaneous T-cell lymphoma, or T-cell leukemias).

Statistical analyses were performed using commercially available software (Version 8.0; Stata Corp, College Station, Tex). For group comparisons of binary data, we used either the χ² test or the Fisher exact test, depending on the sample size; for comparisons of continuous data, we used the Mann-Whitney test. The results were regarded as significant at P<.05. For comparisons of patients with SSc and control subjects, conditional logistic regression was also performed, and matched odds ratios (ORs) with their 95% confidence intervals (CIs) were calculated.

Using TCR-γ PCR DGGE, a monoclonal population of T cells was detected in blood samples from 13 (34%) of 38 consecutive patients with SSc. In the healthy control group, TCR-γ PCR DGGE revealed a monoclonal population of T cells in blood samples from only 3 subjects (4%) (OR, 12.28; 95% CI, 2.76-54.64; P = .001).

Patients with SSc who had a circulating clonal population of T cells were older than those who did not (67 years vs 48 years; P = .04). Among female patients, a history of pregnancy was similar in patients with and without clonal T cells (71% vs 62%; P>.99).

The median duration of SSc was significantly longer in patients with a T-cell clonality than in those without (78 months vs 36 months; P = .01). Moreover, we were able to demonstrate a marked relationship between SSc subtypes and the presence of a circulating clonal population of T cells: 12 (43%) of the 28 patients with lcSSc had a circulating clonal population of T cells, whereas only 1 (10%) of the 10 patients with dcSSc had evidence of T-cell clonality (P<.01).

The prevalence of the following systemic manifestations related to SSc was similar in patients with and without a circulating clonal population of T cells: (1) pitting scars (54% vs 56%; P>.99); (2) esophageal involvement characterized by motor disturbances on esophageal manometry (91% vs 72%; P>.99); (3) interstitial lung disease defined on computed tomograms by bilateral shadowing associated with pulmonary function test abnormalities manifested by restrictive changes (ie, vital capacity, <80%) and a diffusing capacity for carbon monoxide of less than 70% predicted (23% vs 12%; P = .39); (4) articular dysfunction (46% vs 40%; P = .74); and (5) renal crisis (0% vs 8%; P = .53). We also failed to find a significant difference in the degree of SSc severity⁴ between patients with and without a circulating clonal population of T cells (4 vs 4; P = .20).

Finally, no differences were found in the following laboratory values between patients with SSc who had a circulating clonal population of T cells and those who did not: erythrocyte sedimentation rate, 18 mm/h vs 12 mm/h (P = .35); C-reactive protein, 3 mg/L vs 3 mg/L; (P = .35); hemoglobin, 12.9 g/dL vs 13.0 g/dL (8.0 mmol/L vs 8.1 mmol/L) (P = .71); serum urea nitrogen, 15.4 mg/dL vs 14.0 mg/dL (5.5 mmol/L vs 5.0 mmol/L; P = .03). The frequency of anti–Scl-70 antibodies (8% vs 24%; P = .38) and anticentromere antibodies (46% vs 36%; P = .54) was also similar in the 2 groups, respectively.

Although clonality of T cells is more commonly encountered in diseases involving T-cell lineage (eg, cutaneous T-cell lymphoma and T-cell leukemias), it may be associated with other conditions, including autoimmune disorders such as rheumatoid arthritis, as well.⁵ Our study also demonstrated a marked frequency (34%) of clonally expanded T cells in the peripheral blood samples from patients with SSc compared with the general population. Our findings therefore confirm the data of previous authors who have observed clonal T-cell populations in samples of blood¹ and numerous organs (eg, skin and lungs) of 20% to 56% patients with SSc.^{6 - 8}

Previous authors^{1 ,6 - 8} have also suggested that clonal populations of T cells may have a role in the pathogenesis of SSc. In essence, in a recent series, French et al¹ showed that patients with SSc who have detectable expanded clonal T-cell populations in samples of peripheral blood appear more likely to respond to extracorporeal photophoresis. They postulated that these findings reinforce the theory that clonal T cells may be involved in the pathogenesis of SSc, as extracorporeal photophoresis has been reported to be an efficacious therapy in patients with other T-cell disorders, such as the Sézary syndrome (ie, the leukemic form of cutaneous T-cell lymphoma). In our population, no patient underwent photophoresis. In the present study, the demonstration that clonally expanded T cells were more commonly detected in patients with lcSSc than in those with dcSSc is also in accordance with a possible role of clonal T cells in patients with lcSSc. To date, however, the pathogenic properties of these clonal T cells have not been clearly shown in SSc. Finally, it is of interest to note that the presence of clonally expanded T cells in the peripheral blood samples in our study could not be considered as a predictive factor of organ involvement severity in patients with SSc.

Correspondence: Isabelle Marie, MD, PhD, Department of Internal Medicine, Centre Hospitalier Universitaire de Rouen-Boisguillaume, 76031 Rouen CEDEX, France (isabelle.marie@chu-rouen.fr).

Accepted for Publication: July 23, 2004.

Financial Disclosure: None.