Humanized CD52 monoclonal antibody campath-1H as first-line treatment in chronic lymphocytic leukaemia

The humanized CD52 monoclonal antibody Campath-1H was used as first-line therapy in nine patients with progressive chronic lymphocytic leukaemia (CLL). Intravenous ( n  = 5) or subcutaneous ( n  = 4) injections (up to 30 mg/inj.) were given three times a week for a maximum of 18 weeks. Three patients achieved a complete remission (CR) and five patients a partial remission (PR) (response rate 89%). CLL cells were cleared from blood in all patients and from the bone marrow in seven patients. The response duration time was 8+–24+ months. Adverse events were mild except for one patient who developed CMV pneumonitis. All patients developed lymphocytopenia (B and T cells) but other haematological toxicities were negligible. Campath-1H is a highly effective and well-tolerated agent in patients with previously untreated CLL and further studies are warranted.     

Patients with B cell chronic lymphocytic leukaemia have an expanded population of CD4+ perforin expressing T cells enriched for human cytomegalovirus specificity and an effector-memory phenotype

We have previously shown an expansion of cytotoxic antigen‐experienced CD4⁺T cells (CTLs) that express perforin (PF) in the peripheral blood of patients with B cell chronic lymphocytic leukaemia (B‐CLL). Increased frequencies of CD4⁺CTLs have since been attributed to chronic viral infections, particularly, human cytomegalovirus (HCMV). The present study examined the involvement of CD4⁺CTLs in responses to HCMV in B‐CLL, and characterized their differentiation. We studied 36 HCMV seropositive (SP) and seronegative B‐CLL patients and 20 healthy age‐matched individuals. The HCMV reactivity of CD4⁺PF⁺ and CD4⁺PF^? cells was determined by interferon‐gamma expression, and expression of CD45RA and CCR7 was assessed by flow cytometry. Fluorescence in‐situ hybridization was used to measure relative telomere lengths. CD4⁺PF⁺T cell expansion in B‐CLL patients and controls was strongly associated with HCMV seropositivity. CD4⁺PF⁺ compared to CD4⁺PF^? cells from SP B‐CLL patients elicited major histocompatibility complex (MHC) class II‐restricted responses to HCMV. CD4⁺PF⁺T cells from patients and controls were enriched with highly differentiated T‐effector/memory (CCR7^?) and revertant (CCR7^?CD45RA⁺) phenotype. CD4⁺PF⁺T cells from B‐CLL patients had shorter telomeres than CD4⁺PF^?T cells, indicating an extensive replicative history. We conclude that persistent exposure to HCMV antigens in SP B‐CLL patients leads to an expansion of the circulating MHC class II‐restricted CD4⁺PF⁺T cell population with effector/memory phenotype.     

Quantitative alterations of CD8+ T cells in juvenile idiopathic arthritis patients in remission

The study was aimed to investigate whether quantities of CD8⁺ T cell subsets are normal in juvenile idiopathic arthritis (JIA) patients with disease remission compared to age-matched healthy donors (HD) and whether chronological age may have an impact on proportions of naive CD8⁺ T cells. CD8⁺ T cell subsets were analyzed in 17 JIA patients and 32 age-matched HD by flow cytometry. JIA patients showed lower CD3⁺CD8⁺ T cells compared to HD. Total counts of CD8⁺CD28⁺ and CD8⁺CD28⁺CD45RA⁺ T cells were inversely correlated to chronological age in JIA patients and HD. In JIA patients, percentages of CD8⁺CD28⁺CD45RA⁺ T cells and of CD62L-expressing CD8⁺CD28⁺CD45RA⁺ T cells showed a negative correlation with age. The trend to lower CD28⁺CD45RA⁺ T cell proportions in aged JIA patients in remission may reflect a disturbed T cell homeostasis independently of disease activity and may be due to an intrinsic effect in reconstitution of the peripheral T cells.     

Increased frequency of CD4+PD-1+HLA-DR+ T cells is associated with disease progression in CLL

Chronic lymphocytic leukaemia (CLL) patients often have abnormal expansions of CD4⁺ and CD8⁺ T cells and this can be associated with progressive disease. To characterise the key T-cell populations involved in this phenomenon, we used flow cytometry and 11 phenotypic markers to study 74 CLL patients and 14 controls. T cells of CLL patients were more phenotypically complex than those of healthy controls with significant increases in the frequencies of CD4 and CD8 memory T cells expressing exhaustion-, activation- and senescence-associated markers. Multivariate analysis of 111 different T-cell subsets showed that high frequencies of four subsets (three CD8 and one CD4) were associated with shorter progression-free survival. The most significant association was with CD4⁺HLA-DR⁺PD-1⁺ T cells, and patients could be stratified into high- and low-risk groups based on the frequency of these T cells. The expansion of this CD4⁺ subset could not be accounted for by age, cytomegalovirus infection or increases in Treg cells. Overall, these results highlight two relatively simple biomarkers, percentage CD8⁺ and percentage CD4⁺PD-1⁺HLA-DR⁺ T cells, which can be used to risk-stratify CLL patients, independent of other tumour-associated markers. They also provide further evidence for the pivotal role of T cells in modulating the pathology of CLL.     

Interferon-gamma and interleukin-4 reciprocally regulate CD8 expression in CD8+ T cells

The CD8 co-receptor can modulate CD8⁺ T cell function through its contributions to T cell receptor (TCR) binding and signaling. Here we show that IFN-γ and IL-4 exert opposing effects on the expression of CD8α mRNA and surface CD8 protein during CD8⁺ T cell activation. IL-4 caused down-regulation of surface CD8 on ovalbumin (OVA)_257–264-specific TCR-transgenic OT-I CD8⁺ T cells activated with OVA_257–264-coated antigen presenting cells or polyclonal stimuli, and on wild type CD8⁺ T cells activated with polyclonal stimuli. This effect was enhanced in each case when the cells lacked a functional IFN-γ or IFN-γR gene. When WT or IFN-γ-deficient OT-I CD8⁺ T cells were analyzed 9 days after co-injection with control or IL-4-expressing OVA⁺ tumor cells into RAG-2^−/−γc^−/− mice, CD8 levels were highest on WT donor cells from mice that received the control tumor and lowest on IFN-γ-deficient donor cells from mice that received the IL-4-expressing tumor. The latter CD8^low cells displayed markedly impaired binding of OVA_257–264/MHC tetramers and peptide/MHC-dependent degranulation. The data reveal an unexpected role for IFN-γ in tuning the CD8 co-receptor during primary CD8⁺ T cell activation both in vitro and in vivo.     

Upregulation of CD72 expression on CD19+CD27+ memory B cells by CD40L in primary immune thrombocytopenia

CD72 is a co‐receptor of B cells and regulates B cell activation. Although aberrant expression of CD72 has been reported in primary immune thrombocytopenia (ITP), it is uncertain whether this aberrant expression is restricted to specific B cell subsets. Furthermore, the mechanisms that regulate CD72 expression are unknown. In this study, we found higher frequency of CD19⁺ B cells, CD19⁺CD27⁺ memory B cells and lower frequency of CD19⁺CD27⁻ naive B cells in active ITP patients compared with controls and patients in remission. CD72 expression on CD19⁺CD27⁺ cells was upregulated in active ITP patients and correlated with platelet count and anti‐platelet autoantibodies. In vitro, CD40L could specifically induce CD72 upregulation on CD19⁺CD27⁺ B cells. In combination with CD40L, interleukin (IL) 10 and BAFF (also termed TNFSF13B) further enhanced CD72 expression on CD19⁺CD27⁺ B cells, whereas IL21 reduced CD72 upregulation. CD72mRNA expression after CD40L stimulation was increased in ITP patients and controls. Significant increase of CD40L on CD4⁺ T cells was correlated with CD72 expression on CD19⁺CD27⁺ B cells in ITP patients. In conclusion, upregulation of CD72 expression on CD27⁺memory B cells might take part in the pathogenesis of ITP. Elevated CD40L on CD4⁺ cells combined with cytokines might contribute to the upregulation of CD72 expression on CD27⁺memory B cells.     

Cd8high+ (CD57+) T cells in patients with rheumatoid arthritis

Objective. To investigate the development and T cell receptor (TCR) usage of CD8+, CD57+ T cells in rheumatoid arthritis (RA) patients. Methods. Three-color flow cytometry using monoclonal antibodies (MAb) to CD8, CD57 and different TCR V_β gene products. Results. The proportion of CD8+ T cells expressing CD57 (CD57/CD8) was significantly higher in RA patients compared with age-matched controls. Expanded TCR V_β populations were more frequent, and were found in both RA patient—derived CD8^high+(CD57+) and CD8+, CD57– populations. TCR V_β5+ and TCR V_β13+ expansions were present at high frequency (5 of 26 and 7 of 26, respectively). TCR V_β expansions in CD8^high+(CD57+) lymphocytes from RA patients were significantly larger than those in age-matched controls (expansion index 2.38 ± 0.28, n = 41 and 1.63 ± 0.09, n = 32, respectively), and were stable over time. Conclusion. RA leads to an increase in the frequency of expanded CD8+ T cell subsets expressing selected TCR, due to expansion of TCR V_β+ populations in CD8^high+(CD57+) T cells. Their restricted TCR usage suggests potential specificity for RA antigens and, therefore, a potential role in the pathogenesis of RA.     

Competition for self-peptide-MHC complexes and cytokines between naive and memory CD8+ T cells expressing the same or different T cell receptors

To study competition between naïve and memory T cells, we examined proliferation of adoptively transferred naïve CD8⁺ T cells in lymphopenic recipients or recipients containing a clonal population of CD8⁺ T cells. We find a hierarchy in the extent of T cell proliferation that appears to correlate with the strength of T cell receptor (TCR)-self-peptide-MHC (pepMHC) interactions. CD8⁺ T cells also proliferate in recipients containing a full complement of CD8⁺ cells with a different TCR if the transferred T cells experience stronger TCR-self-pepMHC interactions than the resident T cells. Furthermore, CD8⁺ T cells proliferate in recipients that contain memory CD8⁺ cells with a different TCR, but in this case the relative strengths of TCR-self-pepMHC interactions are not as critical. In contrast, CD8⁺ T cells do not proliferate significantly in recipients harboring naïve or memory CD8⁺ cells that bear the same TCR as the transferred cells. These results suggest that, among naïve T cells and between naïve and memory T cells, CD8⁺ cells having the same TCR compete for both self-pepMHC and cytokines, whereas TCR-different CD8⁺ cells compete for cytokines. These competitive relationships probably help maintain the size and TCR diversity of naïve and memory T cell populations required for optimal immune responses.In a normal adult individual, peripheral T cells include both naïve cells that have not yet encountered antigen and antigen-experienced memory T cells. Both the naïve and memory cell compartments are composed of large numbers of T cells that express diverse antigen-specific T cell receptors (TCRs). Naïve T cells are critical for initiating immune responses to novel antigens, whereas memory T cells mount more rapid and vigorous responses on reencountering the same antigens. Because the total number of peripheral T cells is maintained at a relatively constant level (homeostasis) (1, 2), a proper size and sufficient diversity of naïve and memory T cell compartments are critical for the immune system''s ability to respond to unpredictable encounters with an enormous number of different antigens (3). The molecular mechanisms that regulate the size and diversity of naïve and memory T cell compartments are under active investigation but are still not well understood.The number of naïve T cells in the periphery is determined by their production in the thymus and by their survival, proliferation, and differentiation in peripheral lymphoid organs. Studies have shown that the number of T cells remains constant irrespective of whether the pool is oversupplied or undersupplied (4), indicating mechanisms of regulation in the periphery. Indeed, survival of naïve CD4⁺ and CD8⁺ T cells requires both soluble factors, such as IL-7 (5, 6), and interactions between T cells'' TCR and self-peptide-MHC complexes (pepMHC) (MHC class I for CD8⁺ T cells and MHC class II for CD4⁺ T cells) (7-11). The numbers of memory T cells are similarly regulated by their generation, survival, proliferation, and differentiation. Unlike naïve T cells, survival of memory CD4⁺ and CD8⁺ T cells does not appear to require interactions between TCR and self-pepMHC complexes (12-14). Maintenance of a stable number of memory CD8⁺ T cells requires IL-15 (or IL-7 in the absence of IL-15), which stimulates memory CD8⁺ T cells to proliferate and replenish those lost by attrition (6, 15-17). However, neither IL-15 nor IL-7 (or other factors) is known to be required for survival or proliferation of memory CD4⁺ T cells (17).Naïve T cells do not proliferate significantly in normal adults in the absence of cognate foreign antigen (pepMHC complexes, usually with self-MHC plus peptides derived from foreign proteins). However, after severe T cell depletion induced by ionizing radiation, chemotherapy, or virus infection, the residual T cells undergo expansion in the absence of foreign antigens (18, 19). Similarly, proliferation occurs when small numbers of naïve T cells are adoptively transferred into syngeneic lymphopenic hosts, such as mice deficient in recombination activating gene (RAG). The spontaneous T cell proliferation under lymphopenic conditions is often referred to as homeostatic proliferation because it increases cell number, and it also requires IL-7 and interactions between T cells'' TCR with self-pepMHC complexes (5-9, 11, 12). After proliferation in lymphopenic mice, the persisting T cells acquire surface markers and functions characteristic of antigen-induced memory T cells (20-23). Yet, after proliferation, the total T cell numbers in lymphopenic recipients are not restored to the levels found in normal adult mice (24, 25). Hence, we prefer to call this process lymphopenia-induced proliferation and differentiation. Lymphopenia-induced T cell proliferation and differentiation also occurs under normal physiological conditions, as in neonates (26-28), and the process appears to play a role in generating and/or maintaining an appropriate size and diversity of the memory T cell compartment.Adoptive transfer of naïve T cells into lymphopenic mice has been the model of choice to investigate factors that regulate the size and diversity of T cell compartments, because it requires the same factors (IL-7 and cognate self-pepMHC complexes) as those essential for naïve T cell survival. Using this model, two recent studies examined competition among naïve T cells that express different TCRs. In one study, a clonal population of naïve CD4⁺ T cells was adoptively transferred into either RAG^- recipients or transgenic mice expressing a different TCR on CD4⁺ T cells. The transferred CD4⁺ T cells were reported to proliferate to the same extent in the two recipients, although one had no T cells and the other had a relatively normal number of CD4⁺ T cells (29). The transferred CD4⁺ T cells presumably proliferated in the CD4⁺ TCR transgenic mice because the two clonal populations of T cells did not compete for the same self-pepMHC complexes. Because lymphopenia-induced T cell proliferation also requires IL-7, these results suggest that IL-7 was sufficient for proliferation of the introduced CD4⁺ T cells but not the resident CD4⁺ T cells. In the other study, when naïve CD8⁺ T cells expressing one TCR were transferred into CD8⁺ transgenic mice expressing another TCR, or vice versa, the transferred CD8⁺ T cells proliferated to the same extent (30). Although the level of IL-7 in the transgenic hosts does not support the spontaneous proliferation of the resident CD8⁺ T cells, it is apparently sufficient to support proliferation of the transferred CD8⁺ T cells. Based on the assumption that the amount of IL-7 in normal, RAG^-, and TCR transgenic mice is finite and that endogenous naïve T cells compete for IL-7, these results are puzzling and warrant further examination.There is also little known about the factors that regulate the relative size of naïve and memory T cell compartments. Several studies have concluded that naïve and memory CD8⁺ T cell compartments are regulated independently (12, 31, 32). If this conclusion were correct, a mechanism would be required to keep naïve and memory T cells with the same TCR from competing for the same cognate self-pepMHC complexes. That there may be such a mechanism is suggested by the finding that survival of memory T cells does not require interactions between TCR and self-pepMHC (12-14). However, in the absence of TCR-self-pepMHC interactions, memory CD4⁺ T cells lose many of their functional properties (33), suggesting that these interactions normally occur and are essential. Nevertheless, whether naïve and memory T cells with the same TCR compete for self-pepMHC complexes has not been unequivocally demonstrated. Furthermore, memory CD8⁺ T cells express receptors for both IL-7 and IL-15 and can use IL-7 for their survival and proliferation in the absence of IL-15 (6, 17). The purported independent regulation of naïve and memory CD8⁺ T cell compartments would therefore require mechanisms to prevent competition for IL-7 between naïve and memory CD8⁺ T cells. To date, no such mechanism has been found. Thus, whether naïve and memory T cell compartments are regulated independently needs to be reevaluated.In the present study, we investigated competition among naïve CD8⁺ T cells and between naïve and memory CD8⁺ T cells expressing the same or different TCRs. We show that naïve CD8⁺ T cells can undergo limited proliferation when transferred into hosts whose naïve CD8⁺ T cells express a different TCR; whether the transferred T cells proliferate or not depends on the relative strengths of the TCR-self-pepMHC interactions of the two T cell populations. We also show that naïve CD8⁺ T cells proliferate in hosts that harbor memory CD8⁺ T cells with a different TCR, but, in this case, the relative strengths of TCR-self-pepMHC interactions are not as critical. In contrast, naïve CD8⁺ T cells do not proliferate significantly when transferred into hosts with naïve or memory CD8⁺ T cells that bear the same TCR as the transferred cells. Thus, within the naïve T cell compartment and between naïve and memory T cell compartments, CD8⁺ T cells with the same TCR likely compete for cognate self-pepMHC complexes and cytokines, whereas CD8⁺ T cells having different TCR compete for cytokines.     

Interleukin 4 content in chronic lymphocytic leukaemia (CLL) B cells and blood CD8+ T cells from B-CLL patients: impact on clonal B-cell apoptosis

B-chronic lymphocytic leukaemia (CLL) clonal B cells are characterized by resistance to apoptosis. We evaluated clonal B cells and blood T cells for interleukin 4 (IL-4) content as IL-4 is able to increase CLL cell resistance to apoptosis. The content of IL-4 in CD8+ T cells of CLL patients (n = 9) ranged from 37% to 63% of the total CD8+ T cells (mean level of 49% +/- 3.4) compared with a range of 5-10% for control CD8+ T cells. Clonal B cells positive for cytoplasmic IL-4 ranged from 1% to 97% (mean value 57.8 +/- 6.9%). CD8+ T cells and clonal B cells secreted detectable levels of IL-4, but only clonal CLL B cells (n = 4) secreted IL-4 in association with increasing cell numbers. Fludarabine (F-ara-AMP, 0.1-100 micromol/ml) was able to downregulate the IL-4 content of CD8+ T cells, but not clonal B-cell IL-4. Culture supernatant from CLL CD8+ T cells decreased the spontaneous apoptotic rate of clonal B cells that was reversed with anti-IL-4 and soluble IL-4 receptor. These findings show that IL-4 is present in the microenvironment of B-CLL. In addition, use of agents that can interfere with IL-4 presentation to clonal B cells can be effective in increasing clonal B-cell apoptosis.     

Therapeutic B cell depletion impairs adaptive and autoreactive CD4+ T cell activation in mice

CD20 antibody depletion of B lymphocytes effectively ameliorates multiple T cell-mediated autoimmune diseases through mechanisms that remain unclear. To address this, a mouse CD20 antibody that depletes >95% of mature B cells in mice with otherwise intact immune systems was used to assess the role of B cells in CD4⁺ and CD8⁺ T cell activation and expansion in vivo. B cell depletion had no direct effect on T cell subsets or the activation status of CD4⁺ and CD8⁺ T cells in naive mice. However, B cell depletion impaired CD4⁺ T cell activation and clonal expansion in response to protein antigens and pathogen challenge, whereas CD8⁺ T cell activation was not affected. In vivo dendritic cell ablation, along with CD20 immunotherapy, revealed that optimal antigen-specific CD4⁺ T cell priming required both B cells and dendritic cells. Most importantly, B cell depletion inhibited antigen-specific CD4⁺ T cell expansion in both collagen-induced arthritis and autoimmune diabetes mouse models. These results provide direct evidence that B cells contribute to T cell activation and expansion in vivo and offer insights into the mechanism of action for B cell depletion therapy in the treatment of autoimmunity.     

Strong increase in the percentage of the CD8bright+CD28- T-cells and delayed engraftment associated with cyclosporine-induced autologous GVHD

Abstract: Four children with acute lymphoblastic leukaemia had autologous bone marrow (BM) or peripheral stem cell (PSC) transplantation with low dose of cyclosporine (CsA, 1 mg/kg/d i.v. during the first 28 d) to induce an autologous GVHD (auto-GVHD). Two children did not have clinical auto-GVHD and they relapsed 3 and 4 months after treatment. The 2 other children had clinical signs of auto-GVHD (grade I and grade II): they both are in complete remission but after a first normal haematological recovery they had a prolonged period of aplasia until month 9 for 1 patient and still persistent at month 7 in the other case. We studied lymphocyte subsets reconstitution after transplantation in these patients. All patients had an important decrease in the CD4/CD8 ratio related both to a strong decrease in the CD4⁺ cells and a strong increase in the CD8⁺ cells. Most of the CD8⁺ cells were of the CD8^bright+CD28^- phenotype. These CD8^bright+CD28^- T-cells represented from 33% to 68% of the total lymphocytes. We discuss the role of these cells after autologous transplantation with CsA, and wonder if these cells could mediate cytotoxicity. In conclusion, among 4 children who received autologous BM or PBC transplantation with low dose of CsA, we observed a complete remission after an auto-GVHD and a prolonged period of aplasia in 2 patients and a relapse of leukaemia in 2 other patients. All these 4 patients had an increase in the CD8^bright+CD28^- T lymphocytes.     

IFN-γ and TNF-α secretion by CD4+ and CD8+ TCRαβ+ T-cell clones derived early after allogeneic bone marrow transplantation

Abstract: Secretion of the potentially antileukaemic cytokines IFN-γ and TNF-α was investigated for CD4 ⁺ and CD8 ⁺ TCRαβ⁺ T-cell clones derived from 4 leukaemia patients 3–6 weeks after allogeneic BMT. We investigated cytokine secretion in response to the activation signal accessory cells + phytohaemagglutinin + Interleukin 2. All clones derived after BMT were capable of IFN-γ and TNF-α secretion, and both for CD4⁺ (n = 96) and CD8⁺ (n = 8) T cells quantities of IFN-γ and TNF-α were significantly correlated with one another. When comparing the overall results for posttransplant and normal T-cell clones derived from 2 bone marrow donors (n = 65), both CD4⁺ and CD8⁺ TCRαβ⁺ T-cell clones showed increased IFN-γ production, and CD4⁺ but not CD8⁺ clones showed a decreased TNF-α secretion. The results suggest that noncytotoxic T cells derived after allogeneic BMT can produce IFN-γ and TNF-α and may thus be capable of mediating antileukaemic effects.     

In vivo'Purging' of residual disease in CLL with Campath-1H

We assessed the role of human CD52 antibody (Campath-1H) in six patients with chronic lymphocytic leukaemia (CLL) treated to maximal response with purine analogues (fludarabine/deoxycoformycin) in whom persistent leukaemic infiltration of blood and bone marrow had precluded autologous stem cell transplantation. Five patients achieved haematological and histological complete remission following Campath-1H and one had minimal focal residual CLL in a trephine biopsy. Autologous transplantation was performed in two patients without complications and with rapid haemopoietic engraftment. Treatment with Campath-1H may be of value in eradicating residual disease in CLL and may facilitate high-dose therapy in young patients.     

Decrease in CD4+CD25+ and CD8+CD28+ T cells in interstitial pneumonitis associated with rheumatic disease

The expression of CD25 or CD28 on T cells was examined in patients with rheumatic diseases associated with interstitial pneumonitis (IP), in order to investigate the conditions of CD4⁺CD25⁺ regulatory T cells and CD8⁺CD28⁻ suppressor T cells. Fifty-five patients with various rheumatic diseases and 23 normal controls were enrolled. CD4⁺CD25⁺ T cells of patients with IP were significantly decreased in comparison with non-IP patients, and the ratio of CD8⁺CD28⁻ T cells in patients with IP was significantly higher than that in non-IP patients or normal controls. These results for CD8⁺CD28⁻ T cells were in accord with the decrease in CD8⁺CD28⁺ T cells, and may be related to activation-induced CD8⁺CD28⁺ T-cell death. Thus, the abnormality of CD4⁺CD25⁺ regulatory T cells may be related to the pathogenesis of IP, and the survival and activation of CD8⁺ T cells.     

Decrease in CD4+CD25+ and CD8+CD28+ T cells in interstitial pneumonitis associated with rheumatic disease

Abstract

The expression of CD25 or CD28 on T cells was examined in patients with rheumatic diseases associated with interstitial pneumonitis (IP), in order to investigate the conditions of CD4⁺CD25⁺ regulatory T cells and CD8⁺CD28^? suppressor T cells. Fifty-five patients with various rheumatic diseases and 23 normal controls were enrolled. CD4⁺CD25⁺ T cells of patients with IP were significantly decreased in comparison with non-IP patients, and the ratio of CD8⁺CD28^? T cells in patients with IP was significantly higher than that in non-IP patients or normal controls. These results for CD8⁺CD28^? T cells were in accord with the decrease in CD8⁺CD28⁺ T cells, and may be related to activation-induced CD8⁺CD28⁺ T-cell death. Thus, the abnormality of CD4⁺CD25⁺ regulatory T cells may be related to the pathogenesis of IP, and the survival and activation of CD8⁺ T cells.     

Therapeutic implications of variable expression of CD52 on clonal cytotoxic T cells in CD8+ large granular lymphocyte leukemia

Background

T-cell large granular lymphocytic leukemia is a clonal proliferation of cytotoxic T-lymphocytes which often results in severe cytopenia. Current treatment options favor chronic immunosuppression. Alemtuzumab, a humanized monoclonal antibody against glycophosphatidylinositol-anchored CD52, is approved for patients refractory to therapy in other lymphoid malignancies.

Design and Methods

We retrospectively examined treatment outcomes in 59 patients with CD8⁺ T-cell large granular lymphocytic leukemia, 41 of whom required therapy. Eight patients with severe refractory cytopenia despite multiple treatment regimens had been treated with subcutaneous alemtuzumab as salvage therapy. Flow cytometry was used to monitor expression of glycophosphatidylinositol-anchored CD52, CD55, and CD59 as well as to characterize T-cell clonal expansions by T-cell receptor variable β-chain (Vβ) repertoire.

Results

Analysis of the effects of alemtuzumab revealed remissions with restoration of platelets in one of one patient, red blood cell transfusion independence in three of five patients and improvement of neutropenia in one of three, resulting in an overall response rate of 50% (4/8 patients). Clonal large granular lymphocytes exhibited decreased CD52 expression post-therapy in patients refractory to treatment. Samples of large granular lymphocytes collected prior to therapy also unexpectedly had a significant proportion of CD52-negative cells while a healthy control population had no such CD52 deficiency (p=0.026).

Conclusions

While alemtuzumab may be highly effective in large granular lymphocytic leukemia, prospective serial monitoring for the presence of CD52-deficient clonal cytotoxic T-lymphocytes should be a component of clinical trials investigating the efficacy of this drug. CD52 deficiency may explain lack of response to alemtuzumab, and such therapy may confer a survival advantage to glycophosphatidylinositol-negative clonal cytotoxic T-lymphocytes.