Cytotoxic CD4+ T cells in patients with B cell chronic lymphocytic leukemia kill via a perforin-mediated pathway

Background and Objectives: B-cell chronic lymphocytic leukemia (B-CLL) is a clonal expansion of CD5+B cells that accumulate due to their uncontrolled growth and resistance to apoptosis. We have previously shown that up to 50% of blood CD4+ T cells in BCLL patients have a cytotoxicity-related CD28-CD57+ phenotype and high content of both granzyme B and perforin (PF). In this study we investigate the cytotoxic potential of these cells against autologous B-CLL cells. Design and Methods: Blood CD4+ or CD8+ T cells were positively isolated from B-CLL patients and cultured under a range of conditions with autologous purified B-CLL cells and with bispecific [anti-CD3 x anti-CD19] antibodies. Apoptosis of labeled B-CLL cells was assessed using the change of mitochondrial membrane potential with the fluorescent dye DiOC6 and confirmed by annexin V binding. Results: There was time- and dose-dependent killing of B-CLL cells by both CD8+ and CD4+ T cells and this ranged from 6.6 - 68.0% for CD4+ cells and 6.4 - 57.8% for CD8+ cells. Almost complete inhibition by concanamycin A suggests that CD4+ T cells like CD8+ T cells induced apoptosis through a perforin-mediated pathway, but not via Fas/FasL (as indicated by lack of blocking with brefeldin A), tumor necrosis factor or TRAIL. Interpretation and Conclusions: This study shows that blood CD4+PF+ T cells enriched in B-CLL patients, are able to kill autologous B-CLL cells ex vivo, through bispecific antibodies via a perforin mediated mechanism

Internalization of rituximab and the efficiency of B cell depletion in rheumatoid arthritis and systemic lupus erythematosus

Objective: Rituximab, a type I anti-CD20 monoclonal antibody (mAb), induces incomplete B cell depletion in some patients with rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE), thus contributing to a poor clinical response. The mechanisms of this resistance remain elusive. The purpose of this study was to determine whether type II mAb are more efficient than type I mAb at depleting B cells from RA and SLE patients, whether internalization influences the efficiency of depletion, and whether Fc? receptor type IIb (Fc?RIIb) and the B cell receptor regulate this internalization process.Methods: We used an in vitro whole blood B cell–depletion assay to assess the efficiency of depletion, flow cytometry to study cell surface protein expression, and surface fluorescence–quenching assays to assess rituximab internalization, in samples from patients with RA and patients with SLE. Paired t-test or Mann-Whitney U test was used to compare groups, and Spearman's rank correlation test was used to assess correlation.Results: We found that type II mAb internalized significantly less rituximab than type I mAb and depleted B cells from patients with RA and SLE at least 2-fold more efficiently than type I mAb. Internalization of rituximab was highly variable between patients, was regulated by Fc?RIIb, and inversely correlated with cytotoxicity in whole blood B cell–depletion assays. The lowest levels of internalization were seen in IgD– B cells, including postswitched (IgD–CD27+) memory cells. Internalization of type I anti-CD20 mAb was also partially inhibited by anti-IgM stimulation.Conclusion: Variability in internalization of rituximab was observed and was correlated with impaired B cell depletion. Therefore, slower-internalizing type II mAb should be considered as alternative B cell–depleting agents for the treatment of RA and SLE

CD40 antibody evokes a cytotoxic T-cell response that eradicates lymphoma and bypasses T-cell help

CD40 is essential in enabling antigen-presenting cells to process and present antigen effectively to T cells. We demonstrate here that when antibody against CD40 is used to treat mice with syngeneic lymphoma, a rapid cytotoxic T-cell response independent of T-helper cells occurs, with tenfold expansion of CD8 + T cells over a period of 5 days. This response eradicates the lymphoma and provides protection against tumor rechallenge without further antibody treatment. Thus, it seems that by treating mice with monoclonal antibody against CD40, we are immunizing against syngeneic tumors. The phenomenon proved reproducible with two antibodies against CD40 (3/23 and FGK-45) in three CD40+ lymphomas (A20, A31 and BCL1) and gave partial protection in one of two CD40? lymphomas (EL4 and Ten1). Although the nature of the target antigens on these lymphomas is unknown, CD8+ T cells recovered from responding mice showed powerful cytotoxic activity against the target B-cell lymphoma in vitro

The biology of CD20 and its potential as a target for mAb therapy

CD20 is a 33-37 kDa, non-glycosylated phosphoprotein expressed on the surface of almost all normal and malignant B cells. It is also the target for rituximab, the most effective anti-cancer monoclonal antibody developed to date. Rituximab has now been given to over 300,000 lymphoma patients in the last decade and interestingly is now being explored for use in other disorders, such as autoimmune conditions including rheumatoid arthritis and systemic lupus erythematosus. Despite the success in immunotherapy, knowledge about the biology of CD20 is still relatively scarce, partly because it has no known natural ligand and CD20 knockout mice display an almost normal phenotype. However, interesting insight has come from work showing that CD20 is resident in lipid raft domains of the plasma membrane where it probably functions as a store-operated calcium channel following ligation of the B cell receptor for antigen. In the current review, these and data relating to its activity as a therapeutic target will be discussed in depth. It is clear that a greater understanding of CD20 biology and the effector mechanisms, such as antibody-dependent cellular cytotoxicity, complement-dependent cytotoxicity and growth regulation, which operate with anti-CD20 mAb in vivo will allow more efficient exploitation of CD20 as a therapeutic target

CD70 and IFN-1 selectively induce eomesodermin or T-bet and synergize to promote CD8+ T-cell responses

CD70-mediated stimulation of CD27 is an important cofactor of CD4+ T-cell licensed dendritic cells (DCs). However, it is unclear how CD70-mediated stimulation of T cells is integrated with signals that emanate from signal 3 pathways, such as type-1 interferon (IFN-1) and IL-12. We find that while stimulation of CD27 in isolation drives weak EomesoderminhiT-betlo CD8+ T-cell responses to OVA immunization, profound synergistic expansion is achieved by cotargeting TLR. This cooperativity can substantially boost antiviral CD8+ T-cell responses during acute infection. Concomitant stimulation of TLR significantly increases per cell IFN-? production and the proportion of the population with characteristics of short-lived effector cells, yet also promotes the ability to form long-lived memory. Notably, while IFN-1 contributes to the expression of CD70 on DCs, the synergy between CD27 and TLR stimulation is dependent upon IFN-1's effect directly on CD8+ T cells, and is associated with the increased expression of T-bet in T cells. Surprisingly, we find that IL-12 fails to synergize with CD27 stimulation to promote CD8+ T-cell expansion, despite its capacity to drive effector CD8+ T-cell differentiation. Together, these data identify complex interactions between signal 3 and costimulatory pathways, and identify opportunities to influence the differentiation of CD8+ T-cell responses

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.<br/