Absence of CD26 Expression Is a Useful Marker for Diagnosis of T-Cell Lymphoma in Peripheral Blood

Hematopathology / CD26 IN MYCOSIS FUNGOIDES

Dan Jones, MD, PhD,1 Nam H. Dang, MD, PhD,2 Madeleine Duvic, MD,3 LaBaron T. Washington, MD,1 and Yang O. Huh, MD1

Key Words: Mycosis fungoides; Flow cytometry; T-cell lymphoma; Tumor markers Downloaded from https://academic.oup.com/ajcp/article/115/6/885/1758156 by guest on 28 September 2021

Abstract Mycosis fungoides (MF) is a cutaneous lymphoma We report flow cytometric characterization of composed of CD4+ T cells with a skin-homing phenotype. A surface CD26 expression in 271 peripheral blood related disorder, Sézary syndrome (SS), is characterized by samples from 154 patients evaluated for the presence of manifestation as a diffuse erythrodermic rash with substantial a T-cell lymphoproliferative disorder, primarily mycosis numbers of circulating tumor cells. A subset of patients with fungoides/Sézary syndrome (MF/SS). The presence of typical MF also develop SS when the disease progresses. The morphologically identifiable tumor cells on peripheral presence of peripheral blood involvement in MF is a negative blood smears was the criterion for lymphomatous prognostic factor.1,2 Molecular studies have detected evidence involvement. In 66 of 69 samples from 28 patients, we of clonal T cells in the peripheral blood in many patients with identified an abnormal CD26–/dim T-cell population MF, likely representing the circulation of small numbers of that was distinct from the variable CD26 expression tumor cells.2-5 However, the clinical significance of such low- seen in normal peripheral blood T cells. This level peripheral blood involvement, detected only by poly- population was CD26– in 23 patients and weakly merase chain reaction analysis, is unclear given the presence CD26+ in 5 patients. CD7 was more variably expressed of such clones in patients with clinically localized cutaneous in MF/SS tumor cells, allowing recognition of a distinct, disease.6 quantifiable abnormal T-cell population in only 34 of MF/SS in blood has a variety of morphologic appear- 69 involved samples. An increased CD4/CD8 ratio and ances, including small irregular cells, markedly convoluted lower surface expression of CD4 in tumor cells also classic “Sézary” lymphocytes, and larger nucleolated forms. helped separate the CD26–/dim atypical population for Because of this variable appearance, accurate enumeration of quantification. In 35 blood samples from other types of tumor cells by manual differential can be difficult. For these T-cell tumors, tumor cells in 10 of 11 morphologically reasons, flow cytometric analysis is used routinely in many involved cases showed absent/dim CD26. Although centers to identify circulating MF cells in peripheral blood. capable of detecting abnormalities in most cases of Diagnostic criteria have included absolute increases in CD4+ MF/SS, CD7 expression does not provide as clear a T cells, an elevation of the CD4/CD8 ratio, and increases in separation of the neoplastic population and can be the number of CD7– T cells.7-11 However, all of these parame- replaced by CD26 staining in routine peripheral blood ters also can be increased in the peripheral blood in nonneo- flow cytometric screening of MF/SS patients. plastic conditions, including inflammatory dermatoses, hindering the definitive diagnosis of MF/SS or other T-cell tumors.8,9,11 CD26 is a well-characterized surface proteolytic enzyme that is expressed in the majority of lymphocytes in peripheral blood.12 We report that absent or dim CD26 expression is a feature of almost all cases of MF and can be used to allow more sensitive flow cytometric detection and quantitation of tumors cells than the use of CD7.

Materials and Methods cytometers (Becton Dickinson). Ten control samples from healthy blood donors were used to establish the range of We analyzed 271 consecutive peripheral blood samples CD26 and CD7 expression in T-cell populations. In cases (from 154 patients) submitted for evaluation of involvement other than MF, additional antibodies (particularly CD56, by a T-cell lymphoproliferative disorder to the immunology CD57, and T-cell receptor-gamma/delta) were used in 4- laboratory at the University of Texas–M.D. Anderson Cancer color analysis to determine the final diagnosis. Negative Center, Houston, during a 5-month study period (4 months staining levels were set by comparison with an isotype continuous with 1 subsequent month of follow-up). In 83% control antibody. Statistical analysis was performed using the of the cases, correlation was made with the morphologic Fisher exact and the Student t tests and Pearson correlation findings in peripheral blood smears or bone marrow aspirates coefficient measures with Stats Direct Software (Camcode, prepared from a sample from the same day. For the Ashwell, England). remaining cases, comparison was made with peripheral For all samples, analysis was limited to lymphocytes by Downloaded from https://academic.oup.com/ajcp/article/115/6/885/1758156 by guest on 28 September 2021 blood smears from other dates, usually within a week of the using a manual gating strategy based on forward/side scatter analyzed cytometry sample. Lymphoma cells, defined as and side scatter/CD45-PerCP staining properties. Contami- either Sézary cells with markedly convoluted nuclear nation of the lymphocyte gate by monocytes was assessed by contours or enlarged (nucleolated) lymphocytes, were quan- CD45-PerCP/CD14-PE staining. The CD26 and CD7 titated by 100-cell manual differential by one of us (D.J.). staining patterns were analyzed by eye using the CD4- Serial samples from the same patient were examined, when PE/CD26-FITC, CD3-PE/CD26-FITC, CD4-PE/CD7-FITC, available, to establish the characteristic morphologic features and CD3-PE/CD7-FITC dot-plot cytograms. For some cases, of each patient’s tumor. cluster analysis was performed using CellQuest and Paint-a- Diagnoses of patients were MF (94), SS (11, 1 in remis- Gate software (Becton Dickinson). Criteria for an abnormal sion), nodal peripheral T-cell lymphoma (12), cutaneous CD7 or CD26 tumor population included the presence of a anaplastic large cell lymphoma (3), cutaneous T-cell lym- CD4+ T-cell population that was clearly separable from the phoma, not otherwise specified (6), CD8+ leukemia/ normal spectrum of variably positive reactive lymphocytes. lymphoma (2), natural killer cell lymphoma (2), large gran- ular lymphocyte (LGL) leukemia (2), atypical cutaneous Results infiltrate/rule out MF (10), and chronic dermatitis (12). Final diagnoses in all cases were based on overall morphologic and immunophenotypic findings in bone marrow, blood, and CD26 and CD7 Expression in Normal Peripheral Blood tissue samples using criteria from the updated World Health Lymphocytes Organization classification.13 Cases with primary skin In peripheral blood from 10 healthy control subjects, involvement by a CD4+, epidermotropic T-cell tumor were there was a spectrum of CD26 expression in both CD4+ and diagnosed as MF or as Sézary leukemia if there was an CD8+ T cells ❚Image 1A❚. As shown on the CD4/CD26 erythrodermic rash and substantial peripheral blood involve- cytograms, CD26 positivity ranged between 56% and 86% ment (tumor cells >500/µL). The diagnosis of “atypical cuta- of the CD3+CD4+ T-cell population (mean ± SD, 77% ± neous lymphoid infiltrate” was used for cases with clinical 8%). Normal CD8+ lymphocytes showed similar variable features suggestive of MF and/or the presence of a clonal T- surface CD26 expression, with a range of 24% to 80% cell receptor rearrangement by molecular analysis but equiv- showing positive staining (mean ± SD, 52% ± 13% [not ocal histologic findings. At our institution during this period, shown]). CD3+CD56+ T cells also showed variable CD26 we typically performed analysis of peripheral blood samples expression (range, 25%-90%) but CD56+CD3– natural killer for all patients with systemic T-cell lymphoma and patients cells were typically CD26– (up to 10% could be weakly with cutaneous findings suggestive of MF. positive). Variation in the percentage of CD26+ peripheral Three-color flow cytometric analysis was performed on blood T cells in different samples likely was affected by the samples following a standard cell lysis method using mouse degree of activation of the normal lymphocyte populations, a monoclonal antibodies directed against CD45 (peridin- characteristic feature of CD26 expression in mature T cells.14 chlorophyll-a-protein [PerCP]-conjugated), as well as CD7 expression in nonneoplastic T cells was assessed in various combinations of CD26 (fluorescein isothiocyanate 19 normal control samples and showed variable positivity of [FITC]-conjugated, IgG2a clone L272), CD3 (FITC or both CD4+ and CD8+ T cells (Image 1A). CD7 expression phycoerythrin [PE]), CD4 (PE), CD5 (PE), CD7 (FITC), was seen in 73% to 97% of CD4+CD3+ T cells (mean ± SD, CD8 (FITC or PE), and CD19. All antibodies were from 85% ± 6%) in the samples from healthy control subjects. Becton Dickinson, San Jose, CA, unless otherwise stated, CD7 expression was more variable on CD4+ T cells in study and analysis was performed using FACScan or FACSCaliber patients than in control subjects, ranging from 61% to 89%

886 Am J Clin Pathol 2001;115:885-892 © American Society of Clinical Pathologists Hematopathology / ORIGINAL ARTICLE of CD4+CD3+ cells in samples that showed no morphologic the typical continuous, “straight-line” staining pattern on the evidence of tumor. These findings suggest that the effects of CD4-PE/CD26-FITC cytograms. We noted 3 morphologi- treatment, reactive T-cell populations, and concurrent cally normal peripheral blood samples (2 from patients with illnesses (eg, infection) may increase the number of circu- MF, 1 from a patient with an atypical cutaneous T-cell infil- lating CD7– T cells in the absence of circulating tumor. trate) that showed small discrete separable CD4-dim CD26– populations, representing 0.3% to 0.5% of all analyzed cells CD26 and CD7 Expression in MF/SS (data not shown). Overall, CD26 expression was assessed in 271 samples Examination of 69 samples from 28 patients with MF or from 154 patients undergoing initial workup or follow-up for SS with tumor cells in a smear revealed an abnormal popula- a T-cell lymphoproliferative disorder, mostly cutaneous T- tion of T cells on either the CD4/CD26 or the CD4/CD7 cell lymphoma. Comparison was made with morphologic cytograms in 66 samples (96%). In 23 of these patients, this examination of peripheral blood smears done around the population was uniformly CD26– and formed a discrete Downloaded from https://academic.oup.com/ajcp/article/115/6/885/1758156 by guest on 28 September 2021 same time ❚Table 1❚. In all but 3 of the morphologically unin- population separable from the variable CD26 staining of volved blood samples, CD26 expression in T cells showed benign T cells ❚Image 1B❚. In the other 5 patients, the

A 4 104 104 10

3 3 103 10 10

2 2 102 10 10

CD3-PE CD4-PE 1 CD4-PE 1 101 10 10

100 100 100 100 101 102 103 104 100 101 102 103 104 100 101 102 103 104 CD4-FITC CD7-FITC CD26-FITC B

104 104 104

3 103 103 10

102 102 102

CD3-PE CD4-PE CD4-PE 1 101 101 10

100 100 100 100 101 102 103 104 100 101 102 103 104 100 101 102 103 104 CD4-FITCCD7-FITCCD26-FITC C

4 4 10 104 10 3 103 103 10

2 102 102 10

CD3-PE CD4-PE CD4-PE 1 101 101 10

0 0 10 100 10 100 101 102 103 104 100 101 102 103 104 100 101 102 103 104 CD4-FITCCD7-FITCCD26-FITC ❚Image 1❚ CD26 and CD7 expression in peripheral blood T lymphocytes. A, Peripheral blood from a healthy control subject demonstrates variable expression of both CD7 and CD26 in CD4+ T cells. B, Sézary leukemia. Tumor cells demonstrate uniform absence of expression of CD7 and CD26. C, Mycosis fungoides in blood. Dim surface expression of CD4 in tumor cells allows a quantification of clearly separable CD26– and CD7– populations, representing approximately 15% of total events analyzed (21% of the lymphocyte gate). FITC, fluorescein isothiocyanate; PE, phycoerythrin.

❚Table 1❚ CD26 and CD7 Expression in Peripheral Blood of Patients With T-Cell Tumors*

Abnormal Population Detected

Samples With Tumor CD4/CD26 Cytogram CD4/CD7 Cytogram Other Cytometric Underlying Diagnosis Cells in PB Smear Findings

MF/SS 69/212 (32.5) 66/69 (96) (CD26–, 59 cases; 34/69 (49) (CD7–, 18 cases; CD4 low, 11 cases; CD26 dim+, 7 cases) CD7+, 16 cases) CD4–, 3 cases† CD3 low, 4 cases; CD3–, 1 case† Other types of PTCL 11/35 (31) 11/11 (CD26–, 10 cases) 5/11 (45) Abnormal CD4, 2 cases; abnormal CD3, 4 cases; abnormal CD5, 4 cases Chronic dermatitis 0/14 (0) 0/14 (0) 0/14 (0) — Downloaded from https://academic.oup.com/ajcp/article/115/6/885/1758156 by guest on 28 September 2021 Atypical cutaneous 1/10 (10) 1/10 (10)‡ 1/10 (10)‡ CD4 dim, 1 case lymphoid infiltrate

MF, mycosis fungoides; PB, peripheral blood; PTCL, peripheral T-cell lymphoma; SS, Sézary syndrome, * Data are given as number with finding/total (percentage) unless otherwise indicated. † Antigen loss detected in only a subset of the tumor cell population. ‡ Abnormal population represented 1% of all analyzed cells. abnormal population was weakly CD26+ but was separable Serial analyses of peripheral blood samples from from the normal T-cell population because of lower surface patients with MF/SS undergoing treatment showed variations expression of CD4. Only 3 morphologically atypical blood in the numbers of tumor cells counted on smears that paral- samples (all from patients in the patch/plaque stage of MF) leled variations in the size of the abnormal population did not show a discrete abnormal population on the detected by CD4/CD26 surface staining. Especially in CD4/CD26 (or CD3/CD26) cytograms. Two samples were tumors undergoing therapy, morphologic counts tended to involved minimally, showing 1% and 3% identifiable tumor underestimate the percentages of tumor cells present cells, respectively, on manual differential counts of the compared with the flow cytometric detection. However, large smear. The remaining smear had rare lymphocytes (<0.1% of changes in the number of the abnormal CD26–/dim T-cell cells) suggestive of Sézary cells. Comparing MF/SS, populations detected by the flow cytometric method were dermatitis, and atypical cutaneous lymphoid lesions, there paralleled by the findings on the smears. Thus, the CD26– was a strong association between the identification of a sepa- population likely represents the neoplastic population in rable CD26–/dim population and identifiable tumor cells on MF/SS. the peripheral smear (P < .0001). In contrast, CD7 was expressed more variably on Expression of Other T-Cell Markers in MF/SS MF/SS tumor cells. Overall, 34 (49%) of 69 involved blood Other flow cytometric features seen in involved samples samples from 28 patients with MF/SS had a separable, from patients with MF/SS are summarized in Table 1. quantifiable abnormal T-cell population identified by exami- Analysis of the CD3+ T-cell population revealed a CD4/CD8 nation of the CD4/CD7 cytograms ❚Image 1C❚. In the ratio greater than 5 in at least 1 sample from 23 of 28 remaining cases, it was not possible to separate the patients with MF/SS but in only 3 of 139 uninvolved samples abnormal population from the nonneoplastic lymphocytes (P < .0001). This ratio was elevated more frequently in because of variability in CD7 staining ❚Image 2❚. The exis- untreated patients and was less often elevated in patients with tence of an abnormal (neoplastic) population in these cases MF/SS undergoing systemic therapy. It therefore was less usually could be inferred (but not quantified) by relative useful for detecting low-level lymphomatous involvement. increases in the number of CD7– T cells. CD4/CD26 dual Lower level expression of CD4 (compared with the level staining allowed separation of the abnormal T-cell popula- on nonneoplastic T cells) was seen on tumor cells from 14 of tion in all of these cases. There was a single sample in 28 patients (Image 1C). Tumor cells in 3 cases showed which an abnormal population detected by examination of complete absence of CD4 on some tumor cells. In 2 of the CD4/CD7 cytograms was not clearly seen by CD4/CD26 cases, correlation of the results of skin biopsy findings with staining. Overall, 10 of 28 patients with MF/SS showed cluster analysis of the peripheral blood flow cytometric data abnormal (tumor) T-cell populations that were variably or revealed that this absence of CD4 was associated with the uniformly CD7+. In 3 patients, there were variations in the transformed large cell population within the tumor ❚Image 3❚ expression of CD7 in the presumed tumor cells between (other data not shown). CD7 staining in these cases was samples obtained on different dates. confusing to interpret since variable staining of different

888 Am J Clin Pathol 2001;115:885-892 © American Society of Clinical Pathologists Hematopathology / ORIGINAL ARTICLE

A B

104

103

102 CD4-PE

101

100 100 101 102 103 104 Downloaded from https://academic.oup.com/ajcp/article/115/6/885/1758156 by guest on 28 September 2021 CD7-FITC C D

4 104 10

3 103 10

2 102 10 CD4-PE CD4-PE

1 101 10

0 100 10 0 1 2 3 4 100 101 102 103 104 10 10 10 10 10 CD25-FITC CD26-FITC ❚Image 2❚ CD7+ mycosis fungoides in peripheral blood (Wright-Giemsa, ×400). A, Peripheral blood smear shows 58% of total WBCs are intermediate-sized nucleolated tumor cells. B, Tumor cells show variable expression of CD7, overlapping with nonneoplastic lymphocytes (19% of CD4+ T cells are CD7–). Tumor cells are variably CD25+ (C) and uniformly CD26– (80% of gated lymphocytes) (D). FITC, fluorescein isothiocyanate; PE, phycoerythrin. tumor cell populations overlapped with normal CD7 staining recognition of the neoplastic population. Of 7 samples (Image 3D). Dim expression of CD5 was seen in tumor cells analyzed from 3 CD8+ tumors (LGL leukemia, hepato- from 4 of 26 patients (not shown). Tumor cells in 5 patients splenic lymphoma, and 1 unclassifiable tumor), 6 showed with MF/SS showed differences in the expression level of uniform absence of CD26 expression in the tumor cell popu- CD3 compared with their normal T-cell populations (Image lation. One LGL leukemia was CD26+. 1C). In all cases, the aberrant level of surface expression of pan T-cell markers was maintained over sequential tumor Discussion samples during the 4-month study period, providing a stable “signature” of the tumor immunophenotype (not shown). Unequivocal detection of neoplastic T-cell populations by flow cytometric analysis is difficult, given the lack of Flow Cytometric Detection of CD26 in Other Types easily applicable methods for demonstration of clonality. of T-Cell Lymphoproliferative Disorders Nevertheless, clinicopathologically defined subtypes of T- The peripheral blood findings in a small number of cell tumors show characteristic immunophenotypic features samples from patients with other T-cell tumors are summa- that can be used to identify them by multiparameter rized in Table 1. Eleven samples from 7 patients were analysis.13,15 The definitive detection of MF cells is limited involved by morphologic criteria; 10 of 11 of these samples by the absence of specific immunophenotypic markers for showed an abnormal CD26– population on the CD4/CD26 this tumor type. The characteristic MF immunophenotype cytograms, with the remaining case showing an abnormal includes positivity for CD4, CD15s, cutaneous lymphocyte CD26+ population. In the 4 samples from CD4+ peripheral antigen (CLA), CD60, and CXCR3 and absence of expres- T-cell lymphoma, dim CD4 expression was noted in 2, and sion of CD7 and CD49d (VLA-1 integrin).9,16-18 However, dim CD5 and a high level of expression of surface CD3 were all of these markers also are variably present in normal T-cell noted, respectively, in the other 2 samples, allowing easier populations, making quantification of tumor involvement

A B C

1024

768

512

SSC-Height 256

0 Downloaded from https://academic.oup.com/ajcp/article/115/6/885/1758156 by guest on 28 September 2021 0 256 512 768 1024 FSC-Height

D E F

104 104 104

103 103 103

102 102 102 CD4-PE CD3-PE

CD3-PerCP 1 101 101 10

0 100 100 10 0 1 2 3 4 100 101 102 103 104 100 101 102 103 104 10 10 10 10 10 CD26-FITC CD7-FITC CD4-FITC ❚Image 3❚ Mycosis fungoides with dim or absent surface CD4 expression. A, Skin biopsy specimen demonstrates a superficial dermal infiltrate of large neoplastic cells (H&E, ×200), which are mostly CD4– by cryostat section immunohistochemistry (inset, ×1,000). B, Peripheral blood smear reveals that 62% of the lymphocytes are enlarged with prominent nucleoli and irregular nuclear contours (Wright-Giemsa, ×1,000). C, Flow cytometric analysis of peripheral blood demonstrates 73% of the gated lymphocytes are CD3+ T cells, highlighted in color on the scattergram (other cells are shaded in gray). D, CD3/CD7 cytogram shows variable CD7 expression, mimicking the typical distribution in normal T cells. E, CD4/CD3 cytogram demonstrates 2 abnormal populations, CD4 dim (green) and CD4– (red) and a normal CD4+ population (blue). The CD4– population has a larger cell size on the scattergram, consistent with tumor cells. F, CD4/CD26 cytogram shows complete absence of CD26 expression in both abnormal (tumor) populations with variable CD26 expression in normal T cells (blue). In panels not shown, CD19+ B cells represented 25% of gated lymphocytes; CD56+ natural killer cells and CD8+ T cells each made up 0.5% of the lymphoid gate. FITC, fluorescein isothiocyanate; FSC, forward scatter; PE, phycoerythrin; PerCP, peridin-chlorophyll-a-protein; SSC, side scatter.

difficult. We showed that absence of expression of CD26 skin microenvironment, and there is not a good correlation also is highly characteristic of MF/SS tumor cells and that an between the number of CLA-positive cells in the blood and abnormal CD26– population correlates with the presence of the number of Sézary cells counted or the degree of lymph morphologically identifiable tumor cells in the peripheral node involvement in MF.10 Molecular analysis of sorted cell blood (96% sensitivity, 98% specificity). populations has demonstrated that circulating MF tumor The best-studied MF-associated marker is CLA, an cells are present in both the CLA-positive and the CLA- adhesion molecule that mediates the cutaneous localization negative populations. This result is supported by the lability of skin-homing lymphocytes.19 CLA is expressed in most of CLA expression noted on T cells in culture.24 Thus, CLA skin-homing T cells and almost all MF tumor cells within is unlikely to be a highly sensitive antigen for detection of skin, as well as in a small subset of circulating benign circulating MF cells. lymphocytes, especially in patients with chronic The most commonly used method for detection of cuta- dermatitis.20-23 However, MF/cutaneous T-cell lymphoma neous lymphoma circulating in peripheral blood is the (CTCL) tumor cells tend to shed CLA expression outside the absence of CD7 expression on CD4+ T cells. In normal T

890 Am J Clin Pathol 2001;115:885-892 © American Society of Clinical Pathologists Hematopathology / ORIGINAL ARTICLE cells, CD7 is low or absent in most skin-homing lympho- 2. Fraser-Andrews EA, Woolford AJ, Russell-Jones R, et al. cytes and in a variable number of circulating T cells.8,11,25 It Detection of a peripheral blood t cell clone is an independent prognostic marker in mycosis fungoides. J Invest Dermatol. has been reported that the size of the CD7– T-cell population 2000;114:117-121. 4,10 correlates with the extent of disease in MF/CTCL. 3. Dommann SN, Dommann-Scherrer CC, Dours-Zimmermann However, as described, approximately 50% of MF/CTCL MT, et al. Clonal disease in extracutaneous compartments in cases show variable CD7 expression, making tumor cells cutaneous T-cell lymphomas: a comparative study between cutaneous T-cell lymphomas and pseudo lymphomas. Arch difficult to distinguish from normal and nonneoplastic reac- Dermatol Res. 1996;288:163-167. tive T-cell populations.7-9,26 We found that unless the MF 4. Laetsch B, Haffner AC, Dobbeling U, et al. CD4+/CD7– T tumor cells show lower surface expression of CD4 (or CD3 cell frequency and polymerase chain reaction–based clonality or CD5), it is difficult to separate them definitively from assay correlate with stage in cutaneous T cell lymphomas. J Invest Dermatol. 2000;114:107-111. normal T cells by cluster analysis with CD7 staining. In

5. Muche JM, Lukowsky A, Asadullah K, et al. Demonstration Downloaded from https://academic.oup.com/ajcp/article/115/6/885/1758156 by guest on 28 September 2021 contrast, the reproducible low or negative expression of of frequent occurrence of clonal T cells in the peripheral CD26 in MF usually creates a separable discrete cluster of blood of patients with primary cutaneous T-cell lymphoma. Blood. 1997;90:1636-1642. tumor cells that can be recognized. 6. Muche JM, Lukowsky A, Heim J, et al. Demonstration of CD26 (also known as dipeptidyl peptidase IV) is a frequent occurrence of clonal T cells in the peripheral blood widely expressed cell surface proteolytic enzyme related to but not in the skin of patients with small plaque parapsoriasis. cellular activation that is expressed in the majority of circu- Blood. 1999;94:1409-1417. lating T cells.27 As shown herein, CD26 is expressed vari- 7. Bogen SA, Pelley D, Charif M, et al. Immunophenotypic identification of Sézary cells in peripheral blood. Am J Clin ably in most CD4+ circulating T cells, and it is expressed at Pathol. 1996;106:739-748. highest levels on the activated memory-helper T-cell subset, 8. Harmon CB, Witzig TE, Katzmann JA, et al. Detection of but also is expressed at varying levels in CD8+ and immature circulating T cells with CD4+CD7– immunophenotype in T-cell populations.12,28 Absence of CD26 expression has patients with benign and malignant lymphoproliferative dermatoses. J Am Acad Dermatol. 1996;35:404-410. been reported in small numbers of other T-cell tumor types, 9. Scala E, Russo G, Cadoni S, et al. Skewed expression of including adult T-cell leukemia/lymphoma and MF in activation, differentiation and homing-related antigens in skin.9,29-31 Whether CD26 will prove useful for the detection circulating cells from patients with cutaneous T cell of T-cell tumor cells other than MF/SS requires further study. lymphoma associated with CD7– T helper lymphocytes expansion. J Invest Dermatol. 1999;113:622-627. In a small number of cases, we noted absence of CD26 10. Borowitz MJ, Weidner A, Olsen EA, et al. Abnormalities of expression in blood involvement in 5 patients with peripheral circulating T-cell subpopulations in patients with cutaneous T-cell lymphoma and 3 patients with CD8+ tumors. Previ- T-cell lymphoma: cutaneous lymphocyte-associated antigen ously, small studies have demonstrated that CD26 expression expression on T cells correlates with extent of disease. Leukemia. 1993;7:859-863. is associated with certain tumor types—anaplastic large cell 11. Moll M, Reinhold U, Kukel S, et al. CD7-negative helper T lymphoma, precursor T-lymphoblastic lymphoma, and cells accumulate in inflammatory skin lesions. J Invest hepatosplenic lymphoma—that we did not study.31,32 Our Dermatol. 1994;102:328-332. study supports the use of CD26, in place of or in addition to 12. Dang NH, Torimoto Y, Shimamura K, et al. 1F7 (CD26): a marker of thymic maturation involved in the differential CD7, as part of the routine panel for flow cytometric detec- regulation of the CD3 and CD2 pathways of human tion of neoplastic T cells in MF/SS. thymocyte activation. J Immunol. 1991;147:2825-2832. 13. Harris NL, Jaffe ES, Diebold J, et al. World Health From the 1Division of Pathology and Laboratory Medicine and Organization classification of neoplastic diseases of the hematopoietic and lymphoid tissues: report of the Clinical the Departments of 2Lymphoma and 3Dermatology, the University Advisory Committee meeting, Airlie House, Virginia, of Texas–M.D. Anderson Cancer Center, Houston. November 1997. J Clin Oncol. 1999;17:3835-3849. Address reprint requests to Dr Jones: Dept of Hemato- 14. Dang NH, Torimoto Y, Sugita K, et al. Cell surface pathology, Box 72, 1515 Holcombe Blvd, Houston TX 77030. modulation of CD26 by anti-1F7 monoclonal antibody: Acknowledgments: We thank Louise Huck, Linda Powers, analysis of surface expression and human T cell activation. J Immunol. 1990;145:3963-3971. and the entire staff of the M.D. Anderson Cancer Center Immunology and Flow Cytometry Laboratory for their assistance 15. Jones D, O’Hara C, Kraus M, et al. Expression pattern of T- cell–associated chemokine receptors and their chemokines in this work. We thank John T. Manning, MD, for critical review correlates with specific subtypes of T-cell non-Hodgkin of the manuscript. lymphoma. Blood. 2000;96:685-690. 16. Bank I, Rapman E, Shapiro R, et al. The epidermotropic mycosis fungoides associated alpha1beta1 integrin (VLA-1, References CD49a/CD29) is primarily a collagen IV receptor on 1. Bakels V, van Oostveen JW, Gordijn RL, et al. Frequency and malignant T cells. J Cutan Pathol. 1999;26:65-71. prognostic significance of clonal T-cell receptor beta–gene 17. Lu D, Duvic M, Medeiros LJ, et al. The T-cell chemokine rearrangements in the peripheral blood of patients with receptor CXCR3 is expressed highly in low-grade mycosis mycosis fungoides. Arch Dermatol. 1992;128:1602-1607. fungoides. Am J Clin Pathol. 2001;115:413-421.

18. Kamarashev J, Burg G, Kempf W, et al. Comparative analysis 26. Schiavon V, Roth P, Bolton WE, et al. Lymphocytes subsets in of histological and immunohistological features in mycosis normal individuals: analysis by four color immunofluorescence fungoides and Sézary syndrome. J Cutan Pathol. 1998;25:407- and flow cytometry on whole blood. Tissue Antigens. 412. 1996;48(4 pt 1):312-318. 19. Fuhlbrigge RC, Kieffer JD, Armerding D, et al. Cutaneous 27. Buhling F, Kunz D, Reinhold D, et al. Expression and lymphocyte antigen is a specialized form of PSGL-1 expressed functional role of dipeptidyl peptidase IV (CD26) on human on skin-homing T cells. Nature. 1997;389:978-981. natural killer cells. Nat Immun. 1994;13:270-279. 20. Picker LJ, Michie SA, Rott LS, et al. A unique phenotype of 28. Ruiz P, Zacharievich N, Shenkin M. Multicolor cytoenzymatic skin-associated lymphocytes in humans: preferential evaluation of dipeptidyl peptidase IV (CD26) function in expression of the HECA-452 epitope by benign and normal and neoplastic human T-lymphocyte populations. Clin malignant T cells at cutaneous sites. Am J Pathol. Diagn Lab Immunol. 1998;5:362-368. 1990;136:1053-1068. 29. Ruiz P, Mailhot S, Delgado P, et al. CD26 expression and 21. Dworzak MN, Froschl G, Printz D, et al. Skin-associated dipeptidyl peptidase IV activity in an aggressive hepatosplenic

lymphocytes in the peripheral blood of patients with atopic T-cell lymphoma. Cytometry. 1998;34:30-35. Downloaded from https://academic.oup.com/ajcp/article/115/6/885/1758156 by guest on 28 September 2021 dermatitis: signs of subset expansion and stimulation. J Allergy 30. Kondo S, Kotani T, Tamura K, et al. Expression of CD26/ Clin Immunol. 1999;103:901-906. dipeptidyl peptidase IV in adult T cell leukemia/lymphoma 22. Jones D, Benjamin RJ, Shahsafaei A, et al. The chemokine (ATLL). Leuk Res. 1996;20:357-363. receptor CXCR3 is expressed in a subset of B-cell lymphomas 31. Carbone A, Cozzi M, Gloghini A, et al. CD26/dipeptidyl and is a marker of B-cell chronic lymphocytic leukemia. peptidase IV expression in human lymphomas is restricted to Blood. 2000;95:627-632. CD30-positive anaplastic large cell and a subset of T-cell non- 23. Santamaria Babi LF, Picker LJ, Perez Soler MT, et al. Hodgkin’s lymphomas. Hum Pathol. 1994;25:1360-1365. Circulating allergen-reactive T cells from patients with atopic 32. Klobusicka M, Babusikova O. CD26 and DPP IV expression dermatitis and allergic contact dermatitis express the skin- in T acute lymphoblastic leukemia cells: immunocyto- selective homing receptor, the cutaneous lymphocyte- chemistry and enzyme cytochemistry. Gen Physiol Biophys. associated antigen. J Exp Med. 1995;181:1935-1940. 1999;18(suppl 1):34-37. 24. Armerding D, Kupper TS. Functional cutaneous lymphocyte antigen can be induced in essentially all peripheral blood T lymphocytes. Int Arch Allergy Immunol. 1999;119:212-222. 25. Reinhold U, Pawelec G, Fratila A, et al. Phenotypic and functional characterization of tumor infiltrating lymphocytes in mycosis fungoides: continuous growth of CD4+ CD45R+ T- cell clones with suppressor-inducer activity. J Invest Dermatol. 1990;94:304-309.