CD4+CD57+ T Cells Derived from Peripheral Blood Do Not Support Immunoglobulin Production by B Cells

Abstract In Poland, rabbit is a highly valued animal, due to dietetic and flavour values of its meat, but above all, rabbits tend to be commonly used laboratory animals. The aim of the study was developing standards for counts of B-cells with CD19+ receptor, T-cells with CD5+ receptor, and their subpopulations, namely T-cells with CD4+, CD8+ and CD25+ receptor in the peripheral blood of mixed-breed Polish rabbits with addition of blood of meet breeds, including the assessment of the impact of four seasons of the year and animal sex on the values of the immunological parameters determined. The results showed that the counts of B- and T-cells and their subpopulations in peripheral blood remain within the following ranges: for CD19+ B-cells: 1.05 - 3.05%, for CD5+ T-cells: 34.00 - 43.07%, CD4+ T-cells: 23.52 - 33.23%, CD8+ T-cells: 12.55 - 17.30%, whereas for CD25+ T-cells: 0.72 - 2.81%. As it comes to the season of the year, it was observed that it principally affects the values of CD25+ T-cells, while in the case of rabbit sex, more changes were found in females.

Download Full-text

B cell subpopulations separated by CD27 and crucial collaboration of CD27+ B cells and helper T cells in immunoglobulin production

European Journal of Immunology ◽

10.1002/eji.1830270835 ◽

1997 ◽

Vol 27 (8) ◽

pp. 2073-2079 ◽

Cited By ~ 212

Author(s):

Kazunaga Agematsu ◽

Haruo Nagumo ◽

Fen-Chun Yang ◽

Takayuki Nakazawa ◽

Keitaro Fukushima ◽

...

Keyword(s):

T Cells ◽

B Cells ◽

B Cell ◽

Helper T Cells ◽

Immunoglobulin Production ◽

Cell Subpopulations

Download Full-text

Delayed in Vitro Immunoglobulin Production by Cord Lymphocytes

PEDIATRICS ◽

10.1542/peds.65.3.497 ◽

1980 ◽

Vol 65 (3) ◽

pp. 497-500

Author(s):

Yukiaki Miyagawa ◽

Kenichi Sugita ◽

Atsushi Komiyama ◽

Taro Akabane

Keyword(s):

T Cells ◽

T Cell ◽

B Cells ◽

Mononuclear Cells ◽

Pokeweed Mitogen ◽

Immunoglobulin Production ◽

Mitogen Stimulation ◽

Functional Immaturity ◽

Adult Cells

Pokeweed mitogen-induced immunoglobulin (Ig) production by cord lymphocytes was studied in vitro by Ig-secreting plaque-forming cell (Ig-PFC) assay. Although adult mononuclear cells generated all of IgM-, IgG-, and IgA-PFC, cord mononuclear cells generated only IgM-PFC when cultured for seven days. The number of cord IgM-PFC was 102 ± 26/104 mononuclear cells, being about one fourth of that of adult IgM-PFC. When cultured for 14 days, cord mononuclear cells formed increased numbers of IgM-PFC in contrast to adult cells, and yielded IgG-PFC as well, indicating delayed Ig production. Cord T cells were much less effective at helping adult B cells to differentiate into Ig-PFC as compared with adult T cells. Substitution of adult T cells for cord T cell markedly improved the response of cord B cells. The present study demonstrates Ig secretion by cord lymphocytes in response to pokeweed mitogen stimulation. The results further indicate that the delayed Ig production by cord lymphocytes is largely due to functional immaturity of the T cells.

Download Full-text

Distribution of integrins on human peripheral blood mononuclear cells

Blood ◽

10.1182/blood.v74.4.1348.1348 ◽

1989 ◽

Vol 74 (4) ◽

pp. 1348-1354 ◽

Cited By ~ 27

Author(s):

HG Klingemann ◽

S Dedhar

Keyword(s):

T Cells ◽

B Cells ◽

Peripheral Blood Mononuclear Cells ◽

Peripheral Blood ◽

Mononuclear Cells ◽

Human Peripheral Blood ◽

Peptide Sequence ◽

Peripheral Blood Mononuclear ◽

Blood Mononuclear Cells ◽

Beta 1 Integrin

Abstract The receptors for fibronectin (FN-R) and vitronectin (VN-R) belong to a family of integral membrane glycoproteins known to be involved in cell- extracellular matrix and cell-cell interactions named integrins (FN-R = beta 1 integrin and VN-R = beta 3 integrin). Adhesion studies using FN- coated plastic dishes and highly purified subpopulations of peripheral blood mononuclear cells (PBMCs) showed a strong binding of monocytes and T lymphocytes to FN but virtually no binding of B cells to FN. Binding of monocytes and T cells to FN could be partially inhibited by a hexapeptide (GRGDSP) containing the adhesive peptide sequence Arg-Gly- Asp (RGD) as well as by an anti-FN-R antibody. The distribution of beta 1 and beta 3 integrin complexes on PBMCs was characterized by immunoprecipitation of detergent extracts of 125I-labeled cells using polyclonal antibodies against these two receptors. Two surface polypeptides corresponding to the alpha and beta chains of FN-R and VN- R were found on all three cell types. To characterize these receptors further, monoclonal antibodies (MoAbs) against the very late antigens (VLAs) 1, 3, and 5 were used for immunoprecipitation studies. Monocytes and T cells reacted with VLA 5 that was previously identified as the human FN receptor, whereas no labeling with anti-VLA 5 could be shown for B cells. When cell populations were cultured in 10% human serum for 24 hours, an increase in beta 1-integrin+ monocytes and T cells was observed. The number of beta 3-integrin+ cells remained essentially unchanged. The presence of beta 1 and beta 3 integrins on monocytes as well as on T and B lymphocytes may be of significance in the ability of these cells to interact with each other and participate in hematopoiesis and certain immune reactions.

Download Full-text

In VitroMeasles Virus Infection of Human Lymphocyte Subsets Demonstrates High Susceptibility and Permissiveness of both Naive and Memory B Cells

Journal of Virology ◽

10.1128/jvi.00131-18 ◽

2018 ◽

Vol 92 (8) ◽

pp. e00131-18 ◽

Cited By ~ 19

Author(s):

Brigitta M. Laksono ◽

Christina Grosserichter-Wagener ◽

Rory D. de Vries ◽

Simone A. G. Langeveld ◽

Maarten D. Brem ◽

...

Keyword(s):

T Cells ◽

B Cells ◽

B Cell ◽

Immune Suppression ◽

Peripheral Blood ◽

Measles Virus ◽

Memory B Cells ◽

T And B Cells ◽

B Cell Subsets

ABSTRACTMeasles is characterized by a transient immune suppression, leading to an increased risk of opportunistic infections. Measles virus (MV) infection of immune cells is mediated by the cellular receptor CD150, expressed by subsets of lymphocytes, dendritic cells, macrophages, and thymocytes. Previous studies showed that human and nonhuman primate memory T cells express higher levels of CD150 than naive cells and are more susceptible to MV infection. However, limited information is available about the CD150 expression and relative susceptibility to MV infection of B-cell subsets. In this study, we assessed the susceptibility and permissiveness of naive and memory T- and B-cell subsets from human peripheral blood or tonsils toin vitroMV infection. Our study demonstrates that naive and memory B cells express CD150, but at lower frequencies than memory T cells. Nevertheless, both naive and memory B cells proved to be highly permissive to MV infection. Furthermore, we assessed the susceptibility and permissiveness of various functionally distinct T and B cells, such as helper T (TH) cell subsets and IgG- and IgA-positive memory B cells, in peripheral blood and tonsils. We demonstrated that TH1TH17 cells and plasma and germinal center B cells were the subsets most susceptible and permissive to MV infection. Our study suggests that both naive and memory B cells, along with several other antigen-experienced lymphocytes, are important target cells of MV infection. Depletion of these cells potentially contributes to the pathogenesis of measles immune suppression.IMPORTANCEMeasles is associated with immune suppression and is often complicated by bacterial pneumonia, otitis media, or gastroenteritis. Measles virus infects antigen-presenting cells and T and B cells, and depletion of these cells may contribute to lymphopenia and immune suppression. Measles has been associated with follicular exhaustion in lymphoid tissues in humans and nonhuman primates, emphasizing the importance of MV infection of B cellsin vivo. However, information on the relative susceptibility of B-cell subsets is scarce. Here, we compared the susceptibility and permissiveness toin vitroMV infection of human naive and memory T- and B-cell subsets isolated from peripheral blood or tonsils. Our results demonstrate that both naive and memory B cells are more permissive to MV infection than T cells. The highest infection levels were detected in plasma cells and germinal center B cells, suggesting that infection and depletion of these populations contribute to reduced host resistance.

Download Full-text

Oropouche Virus Infects, Persists and Induces IFN Response in Human Peripheral Blood Mononuclear Cells as Identified by RNA PrimeFlow™ and qRT-PCR Assays

Viruses ◽

10.3390/v12070785 ◽

2020 ◽

Vol 12 (7) ◽

pp. 785

Author(s):

Mariene Ribeiro Amorim ◽

Marjorie Cornejo Pontelli ◽

Gabriela Fabiano de Souza ◽

Stéfanie Primon Muraro ◽

Daniel A. Toledo-Teixeira ◽

...

Keyword(s):

T Cells ◽

B Cells ◽

Peripheral Blood Mononuclear Cells ◽

Peripheral Blood ◽

Mononuclear Cells ◽

Peripheral Blood Mononuclear ◽

Human Leukocytes ◽

Qrt Pcr ◽

Viral Antigens ◽

Blood Mononuclear Cells

Oropouche orthobunyavirus (OROV) is an emerging arbovirus with a high potential of dissemination in America. Little is known about the role of peripheral blood mononuclear cells (PBMC) response during OROV infection in humans. Thus, to evaluate human leukocytes susceptibility, permissiveness and immune response during OROV infection, we applied RNA hybridization, qRT-PCR and cell-based assays to quantify viral antigens, genome, antigenome and gene expression in different cells. First, we observed OROV replication in human leukocytes lineages as THP-1 monocytes, Jeko-1 B cells and Jurkat T cells. Interestingly, cell viability and viral particle detection are maintained in these cells, even after successive passages. PBMCs from healthy donors were susceptible but the infection was not productive, since neither antigenome nor infectious particle was found in the supernatant of infected PBMCs. In fact, only viral antigens and small quantities of OROV genome were detected at 24 hpi in lymphocytes, monocytes and CD11c+ cells. Finally, activation of the Interferon (IFN) response was essential to restrict OROV replication in human PBMCs. Increased expression of type I/III IFNs, ISGs and inflammatory cytokines was detected in the first 24 hpi and viral replication was re-established after blocking IFNAR or treating cells with glucocorticoid. Thus, in short, our results show OROV is able to infect and remain in low titers in human T cells, monocytes, DCs and B cells as a consequence of an effective IFN response after infection, indicating the possibility of leukocytes serving as a trojan horse in specific microenvironments during immunosuppression.

Download Full-text

Mezagitamab Induces Immunomodulatory Effect in Patients with Relapsed/Refractory Multiple Myeloma (RRMM)

Blood ◽

10.1182/blood-2020-140527 ◽

2020 ◽

Vol 136 (Supplement 1) ◽

pp. 9-9

Author(s):

Michael Abadier ◽

Jose Estevam ◽

Deborah Berg ◽

Eric Robert Fedyk

Keyword(s):

Bone Marrow ◽

T Cells ◽

B Cells ◽

Nk Cells ◽

Peripheral Blood ◽

Immune Cell ◽

Cell Populations ◽

Landscape Changes ◽

Ki 67 ◽

Immune Cell Subsets

Background Mezagitamab is a fully human immunoglobulin (Ig) G1 monoclonal antibody with high affinity to CD38 that depletes tumor cells expressing CD38 by antibody- and complement-dependent cytotoxicity. CD38 is a cell surface molecule that is highly expressed on myeloma cells, plasma cells, plasmablasts, and natural killer (NK) cells, and is induced on activated T cells and other suppressor cells including regulatory T (Tregs) and B (Bregs) cells. Data suggest that immune landscape changes in cancer patients and this may correlate with disease stage and clinical outcome. Monitoring specific immune cell subsets could predict treatment responses since certain cell populations either enhance or attenuate the anti-tumor immune response. Method To monitor the immune landscape changes in RRMM patients we developed a mass cytometry panel that measures 39-biomarkers to identify multiple immune cell subsets, including T cells (naïve, memory, effector, regulatory), B cells (naïve, memory, precursors, plasmablasts, regulatory), NK cells, NKT cells, gamma delta T cells, monocytes (classical, non-classical and intermediate), dendritic cells (mDC; myeloid and pDC; plasmacytoid) and basophils. After a robust analytical method validation, we tested cryopreserved peripheral blood and bone marrow mononuclear cells from 19 RRMM patients who received ≥ 3 prior lines of therapy. Patients were administered 300 or 600 mg SC mezagitamab on a QWx8, Q2Wx8 and then Q4Wx until disease progression schedule (NCT03439280). We compared the percent change in immune cell subsets at baseline versus week 4 and week 16. Results CD38 is expressed at different levels on immune cells and sensitivity to depletion by mezagitamab generally correlates positively with the density of expression. CD38 is expressed at high densities on plasmablasts, Bregs, NK-cells, pDC and basophils at baseline and this was associated with reductions in peripheral blood and bone marrow (plasmablasts, 95%, Bregs, 90%, NK-cells, 50%, pDC, 55% and basophils, 40%) at week 4 post treatment. In contrast, no changes occurred in the level of total T-cells and B-cells, which is consistent with low expression of CD38 on most cells of these large populations. Among the insensitive cell types, remaining NK-cells acquired an activated, proliferative and effector phenotype. We observed 60-150% increase in activation (CD69, HLA-DR), 110-200% increase in proliferation (Ki-67), and 40-375% increase in effector (IFN-γ) markers in peripheral blood and bone marrow. Importantly, NK-cells which did not express detectable CD38, also exhibited a similar phenotype possibly by a mechanism independent of CD38. Consistent with these data, the remaining CD4 and CD8 T-cell populations exhibited an activated effector phenotype as observed by 40-200% increase in activation, 60-200% increase in proliferation and 40-90% increase in effector markers in peripheral blood. A potential explanation for this acquisition of activated effector phenotypes could be a reduction in suppressive regulatory lymphocytes. Next, we measured levels of Tregs and Bregs, and observed that Bregs which are CD24hiCD38hi were reduced to 60-90% in peripheral blood and bone marrow. In contrast, total Tregs were reduced by only 5-25% because CD38 expression in Tregs appears as a spectrum where only ~10-20% are CD38+, and thus CD38+ Tregs were reduced more significantly (45-75%), reflecting the selectively of mezagitamab to cells expressing high levels of CD38. CD38+ Tregs are induced in RRMM patients, thus we looked at the phenotype of CD38-, CD38mid, and CD38high -expressing Tregs. We observed higher level of markers that correlate with highly suppressive Tregs such as Granzyme B, Ki-67, CTLA-4 and PD-1 in CD38high Tregs. Accordingly, the total Treg population exhibited a less active phenotype after exposure to mezagitamab, which selectively depleted the highly suppressive CD38+ Tregs. Conclusions Chronic treatment with mezagitamab is immunomodulatory in patients with RRMM, which is associated with reductions in tumor burden, subpopulations of B and T regulatory cells, and characterized by conventional NK and T cells exhibiting an activated, proliferative and effector phenotype. The immune landscape changes observed is consistent with the immunologic concept of converting the tumor microenvironment from cold-to-hot and highlights a key mechanistic effect of mezagitamab. Disclosures Berg: Takeda Pharmaceuticals Inc: Current Employment.

Download Full-text

Plasma and Intracellular Concentration of TNF and Its Receptors in Peripheral Blood and Bone Marrow in Different Stages of B-CLL.

Blood ◽

10.1182/blood.v104.11.4781.4781 ◽

2004 ◽

Vol 104 (11) ◽

pp. 4781-4781

Author(s):

Jacek Rolinski ◽

Agnieszka Bojarska-Junak ◽

Iwona Hus ◽

Anna Dmoszynska

Keyword(s):

Bone Marrow ◽

T Cells ◽

B Cells ◽

B Lymphocytes ◽

Peripheral Blood ◽

Biological Effects ◽

Leukemic Cells ◽

Control Group ◽

Stage Of Disease ◽

Positive Correlation

Abstract TNF has been proposed to play a role in the regulation of growth and death of leukemic B-CLL cells. However, the biological effects of TNF on leukemic cells, as well as its role as a prognostic factor need to be further investigated. The aim of the study was to eevaluate the correlation of TNF and its receptors in peripheral blood (PB) and bone marrow (BM) with the stage of B-CLL and some other clinical parameters. PB and BM were taken from 44 newly diagnosed, untreated B-CLL. patients. The control group consisted of 20 healthy subjects. We used flow cytometry technique to assess the capability of T and B lymphocytes to produce TNF and ELISA method to measure plasma levels of TNF and their soluble receptors. We found, that PB and BM plasma TNF concentration in the patients was significantly higher than in the healthy control (2.61 pg/ml. vs 0.62 pg/ml; and 2.91 pg/ml vs 0.75 pg/ml, respectively p<0.001). TNF concentration in PB and BM was significantly higher in Rai stage III–IV than in early stages (p<0.01). There was a correlation between the PB and BM TNF level and lymphocytosis (p<0.005) and the total tumor mass (TTM) (p<0.0001). The PB and BM TNF concentration positively correlated with the percentage of T CD3+ lymphocytes producing intracellular TNF (p<0.01). The percentage of T cells from PB an BM expressing cytoplasmic TNF was significantly higher in patients (PB:39.11±16.97%; BM:40.73±18.19%) than in normal controls (PB:15.74±7.95%; BM:18.80±12.93%) (p< 0.00001; p<0.005, respectively). In PB and BM from B-CLL patients the percentage of CD3+ cells expressing intracellular TNF was significantly higher than the percentage of CD19+/TNF+ cells (p<0.0001). Besides, it was found that the percentage of T cells expressing cytoplasmic TNF positively correlated with the stage of disease (p<0.01). In PB positive correlation were found between the number of T CD3+/TNF+ cells and lymphocytosis (p<0.05) and TTM (p<0.001). The percentage of leukaemic B cells positive for TNF did not correlate with the stage of disease. There was increased expression of TNF-RI and TNF-RII in leukaemic B cells in comparison to normal B-cells was observed (p<0.0001). We found positive correlation between the number of CD5+ B lymphocytes and the levels of soluble TNF-RII (sTNF-RII) (p< 0.05). The sTNF-RII levels in PB and BM significantly correlated with the stage of disease acc. Rai (p<0.0001). Furthermore, the sTNF-RII concentration positively correlated with lymphocytosis and TTM (p<0.0001). These results strongly support the key role TNF in B-CLL pathogenesis. Our results suggest that TNF may function as growth factor for B-CLL cells. CD3+T cells may be the important source of this cytokine in advanced B-CLL. It seems that changes in T cells capability to produce cytoplasmic TNF are associated with disease progression. However, further studies are required to confirm the key role of TNF in B-CLL pathogenesis.

Download Full-text

IGHV Unmutated Chronic Lymphocytic Leukemia (CLL) B Cells Are More Susceptible to Spontaneous Apoptosis Than Mutated CLL B Cells and Are Subject to the Anti-Apoptotic Effect of Environmental Signals

Blood ◽

10.1182/blood.v116.21.2431.2431 ◽

2010 ◽

Vol 116 (21) ◽

pp. 2431-2431

Author(s):

Marta Coscia ◽

Francesca Pantaleoni ◽

Chiara Riganti ◽

Candida Vitale ◽

Micol Rigoni ◽

...

Keyword(s):

T Cells ◽

B Cells ◽

Board Of Directors ◽

Stromal Cells ◽

Peripheral Blood ◽

Research Funding ◽

Lymphocytic Leukemia ◽

Leukemic Cells ◽

Spontaneous Apoptosis ◽

Advisory Committees

Abstract Abstract 2431 Chronic lymphocytic leukemia (CLL) is a clinically heterogeneous disease. A very reliable prognosticator is the mutational status of the tumor immunoglobulin heavy chain variable region (IGHV): patients with unmutated (UM) IGHV have a worse prognosis than patients with mutated (M) IGHV. Soluble factors (i.e. IL-4 and CD40L) and cellular components of the local microenvironment [i.e. bone marrow stromal cells (BMSC) and nurse-like cells (NLCs)] are important survival factors for CLL B cells. It is currently unknown to what extent UM and M CLL cells depend on the local microenvironment for their survival. We have evaluated the spontaneous apoptotic rate of tumor cells isolated by immunomagnetic selection from the peripheral blood (PB) of M and UM CLL patients. Both M and UM CLL B cells underwent spontaneous apoptosis throughout the culture period. However, the UM CLL B cells showed a significantly higher degree of apoptosis in 7-day cultures as compared to M CLL B cells. In both M and UM CLL B cells, high basal levels of Bcl-2 expression and NF-kB activity were detected. On day 7, the percentage of Bcl-2+ leukemic cells was significantly lower in UM than in M CLL B cells. EMSA test showed that NF-kB was totally inactivated in UM CLL B cells and only partially reduced in M CLL B cells. Quantitative analysis of RelA and RelB subunits showed that NF-kB inactivation in UM CLL B cells consisted in a strong reduction of both RelA and RelB nuclear expression. CD40L, IL-4 and stromal cells significantly improved UM CLL B cells viability and significantly recovered Bcl-2 expression. The protective effect exerted by these stimuli was totally independent from the recovery of NF-kB expression. Indeed, after 7 days of culture, the UM CLL B cells had completely lost the nuclear form of NF-kB, and none of the stimuli was capable of restoring it. We observed that UM CLL cells were less susceptible to spontaneous apoptosis when cultured as unfractionated peripheral blood mononuclear cells (M or UM PBMC) as compared to purified leukemic cells (M and UM CLL B cells). The reduced apoptosis detected in UM PBMC was accompanied by a retained expression of Bcl-2 and by a restored activity of NF-kB and suggested the presence of a pro-survival element in the peripheral blood of these patients. To investigate the role of NLC in rescuing UM CLL B cells from apoptosis we first evaluated whether M and UM PBMC generated NLC with the same efficiency. Unexpectedly, the former generated significantly higher numbers of NLC than UM PBMC. Despite the lack of generation of NLC, CLL B cells viability was very similar in the non-adherent fraction of M and UM PBMC on day 7 and 14 of culture. This observation ruled out a role for NLC in supporting UM CLL B cells survival. Conversely, a pro-survival effect on UM CLL B cells was exerted by autologous T cells. Indeed, a significant reduction in the apoptotic rate of leukemic cells was observed when purified UM CLL B cells were cultured in the presence of autologous peripheral blood T cells (UM CLL B cell/T cell co-cultures). NF-kB activity was completely lost in UM CLL B cells cultured for 7 days in medium alone whereas it was restored in UM CLL B cells / T cells co-cultures. The prosurvival effect of circulating T cells was exerted both in cell-to-cell contact and in trans-well condition and was associated to increased secretions of tumor necrosis factor-alpha (TNF-α), platelet-derived growth factor (PDGF)-BB and interleukin-8 (IL-8) as detected by analyses of supernatants through a Multiplex system. These data indicate that despite their more aggressive features, UM CLL B cells are more susceptible to spontaneous apoptosis and depend from environmental prosurvival signals. This vulnerability of UM CLL B cells can be exploited as a selective target of therapeutic interventions. Disclosures: Boccadoro: Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Janssen-Cilag: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding. Massaia: Novartis: Honoraria, Research Funding.

Download Full-text

Non-Cognate Cytotoxic T Cells Can Be Retargeted Against CD20 Positive Tumour Cells Using [Fab' × MHC Class I/Peptide] Conjugates.

Blood ◽

10.1182/blood.v116.21.2838.2838 ◽

2010 ◽

Vol 116 (21) ◽

pp. 2838-2838

Author(s):

Angela D Hamblin ◽

Ben CR King ◽

Ruth R French ◽

Claude H Chan ◽

Alison L Tutt ◽

...

Keyword(s):

T Cells ◽

B Cells ◽

B Cell ◽

Mhc Class I ◽

Peripheral Blood ◽

Class I ◽

B Cell Depletion ◽

Cytokine Release ◽

Anti Cd20

Abstract Abstract 2838 To circumvent cytotoxic T lymphocyte (CTL) tolerance of tumour-associated antigens, the concept of redirecting CTLs against non-cognate targets has developed. One way of doing this is to use bispecific antibodies comprising anti-CD3 and anti-tumour antigen moieties. Unfortunately, this is frequently associated with unacceptable toxicity due to inflammatory cytokine release. As an alternative our approach has been to use a bivalent conjugate recognising a tumour antigen (through an antibody fragment) and a defined population of CTLs (specific for a single antigenic peptide e.g. viral epitope) through peptide presented in the context of recombinant MHC class I. We have produced a conjugate consisting of an anti-human CD20 Fab' fragment joined via a chemical crosslinker (succinimidyl-4-(N-maleimidomethyl) cyclohexane-1-carboxylate) to murine MHC class I/peptide (Kbα1-α3 domains/β2microglobulin presenting the ovalbumin-derived peptide SIINFEKL; expressed bacterially as a continuous polypeptide single chain trimer after Yu et al, J Immunol 2002). Size exclusion chromatography allowed purification of conjugates with [Fab':MHC class I/peptide] ratios of 1:1 and 2:1 (F2 and F3 respectively). In vitro both constructs were able to redirect the transgenic murine CTL line OT-1 (specific for KbSIINFEKL) to lyse human CD20+ tumour cells (lymphoblastoid Daudi cell line) at effector: target ratios of 10:1. This lysis could be blocked by the addition of 100 fold excess of either anti-CD20 F(ab')2 or the Kb/SIINFEKL-specific antibody 25D1. The constructs were also able to cause in vitro proliferation of naïve OT-1 cells (but not irrelevant CD8+ T cells) in the presence of human CD20+ cells in both thymidine incorporation and CFSE dilution assays. Using a human CD20 transgenic mouse model (Ahuja et al, J Immunol 2007) we have evaluated both constructs in vivo for their ability to redirect adoptively transferred OT-1 cells to deplete B cells from the peripheral blood. A single dose of 1 nmole F3 and 2 nmole F2 caused respectively up to 95% and 85% B cell depletion at day 7. The efficacy of lower doses suggested a dose: response relationship. As a marker of toxicity, we have measured cytokine levels at 2, 8 and 24 hours following a dose of 1 nmole F3 and compared them to those seen after administration of an [anti-CD3 × anti-CD20] bispecific F(ab')2 at a dose (0.5 nmole) which produced similar day 7 peripheral blood B cell depletion: phosphate-buffered saline was given as a negative control. Maximal cytokine release was seen at 2 hours with the levels of IL-4, IL-5, KC, IL-2 and IL-10 being lower after administration of the F3 than after the bispecific F(ab')2. However, interestingly, the F3 resulted in greater IL-12 release. Overall these data suggest that [Fab' × MHC class I/peptide] constructs have the potential to redirect non-cognate CTLs to deplete CD20+ malignant B cells from the peripheral blood and that this is associated with a lower level of cytokine release than a similarly efficacious dose of an anti-CD3-containing bispecific F(ab')2. Furthermore, the ability of [Fab' × MHC class I/peptide] constructs to cause proliferation of OT-1 cells in vitro suggests it may be possible to use a single molecule to both generate a secondary cytotoxic T cell response and subsequently to retarget it, increasing the viability of the approach if adopted in the clinic. Disclosures: No relevant conflicts of interest to declare.

Download Full-text