Changes in T-cell receptor VB repertoire in aplastic anemia: effects of different immunosuppressive regimens

Abstract

We studied the degree and the pattern of skewing of the variable region of ␤-chain (VB) T-cell receptor (TCR) repertoire in aplastic anemia (AA) at initial presentation and after immunosuppression using a high-resolution analysis of the TCR VB complementarity-determining region 3 (CDR3). Age-matched healthy individuals and multitransfused patients with nonimmune-mediated hematologic diseases were used as controls. In newly diagnosed AA, the average frequency of CDR3 size distribution deviation indicative of oligoclonal T-cell proliferation was increased (44% ؎ 33% vs 9% ؎ 9%; P ‫؍‬ .0001); AA patients with human leukocyte antigen (HLA)-DR2 and those with expanded paroxysmal nocturnal hemoglobinuria clones showed more skewed VB repertoires. Nonrandom oligoclonal patterns were found for VB6, VB14-16, VB21, VB23, and VB24 subfamilies in more than 50%, and for VB15, VB21, and VB24 in more than 70% of AA patients with HLA-DR2. Patients received immunosuppression with antithymocyte globulin (ATG)/ cyclosporine (CsA) or cyclophosphamide (CTX) with CsA in combination, and their VB repertoire was reanalyzed after treatment. Whereas no significant change in the degree of VB skewing in patients who had received ATG was seen, patients treated with CTX showed a much higher extent of oligoclonality within all VB families, consistent with a profound and longlasting contraction of the T-cell repertoire. VB analysis did not correlate with the lymphocyte count prior to lymphocytotoxic therapy; however, after therapy the degree of VB skewing was highly reflective of the decrease in lymphocyte numbers, suggesting iatrogenic gaps in the VB repertoire rather than the emergence of clonal dominance. Our data indicate that multiple specific clones mediate the immune process in AA. (Blood. 2002; 99:3668-3675)

Preferential suppression of trisomy 8 compared with normal hematopoietic cell growth by autologous lymphocytes in patients with trisomy 8 myelodysplastic syndrome

“…CD8 cell expansion in BM was limited to 1 or 2 V␤ subfamilies, which almost always were also overrepresented in the PB (data not shown); 1 patient had expanded BM V␤ not present in blood. Based on our previously published experience in AA 10,28,36 and our current flow cytometry results, all V␤ families overrepresented by more than 2 SD from the mean of control in the CD28 dim compartment were considered likely to represent oligoclonal or monoclonal expansion of disease-specific CD4 ϩ or CD8 ϩ T cells. CDR3 spectratyping in the expanded V␤ subfamilies was performed in 9 patients with trisomy 8, and skewing of the repertoire was seen in many of the expanded V␤ subfamilies (Figure 2).…”

IFN-γ causes aplastic anemia by altering hematopoietic stem/progenitor cell composition and disrupting lineage differentiation

“…19 Although we observed a slight expansion in 4 Vb subfamilies in CD4 T cells and 2 Vb subfamilies in CD8 T cells in ARE-del BM, both the percentage of expansion and the expansion ratio (CD4: 27%, CD8: 17%) in AREdel mice are much lower compared with that previously reported in AA patients (expansion ratio, 40% to 80%) (supplemental Figure 2). 17,19 In addition, histopathological examination of the spleen, thymus, and lymph nodes revealed structural damage and apparent atrophy (supplemental Figure 3), a characteristic reported in congenital AA animal models, which implies that ARE-del mice are severely immunodeficient. 20 To summarize, the absence of T-cell infiltration in the BM, nonresponsive BM T cells, no abnormal BM T-cell expansion, and general immunodeficiency indicate that T cells are unlikely the cause of AA in ARE-del mice.…”

“…Because an abnormal T-cell repertoire has been reported in AA patients, we characterized the ARE-del BM T-cell repertoire by flow cytometric methods using antibodies that detect different TCR Vb chains. [16][17][18] Abnormal expansions of Vb-expressing T cells were defined as values greater than the mean obtained from WT animals plus 2 3 standard deviation as previously described. 19 Although we observed a slight expansion in 4 Vb subfamilies in CD4 T cells and 2 Vb subfamilies in CD8 T cells in ARE-del BM, both the percentage of expansion and the expansion ratio (CD4: 27%, CD8: 17%) in AREdel mice are much lower compared with that previously reported in AA patients (expansion ratio, 40% to 80%) (supplemental Figure 2).…”

Pathologic clonal cytotoxic T-cell responses: nonrandom nature of the T-cell–receptor restriction in large granular lymphocyte leukemia

“…Therefore, LGL leukemia can serve as a simplified model of natural and less exaggerated polyclonal CTL responses. Such processes may include, for example, typical aplastic anemia 53 and classic autoimmune diseases such as rheumatoid arthritis and multiple sclerosis. [54][55][56][57] Of note is that in all of these conditions, evolution of LGL leukemia has been described, 45,47,[58][59][60] and the LGL clone may have evolved from an initially polyclonal process.…”