A secreted PD-L1 splice variant that covalently dimerizes and mediates immunosuppression

Targeting immune checkpoint pathways, such as programmed death ligand-1 (PD-L1, also known as CD274 or B7-H1) or its receptor programmed cell death-1 (PD-1) has shown improved survival for patients with numerous types of cancers, not limited to lung cancer, melanoma, renal cell carcinoma, and Hodgkin lymphoma. PD-L1 is a co-inhibitory molecule whose expression on the surface of tumor cells is associated with worse prognosis in many tumors. Here we describe a splice variant (secPD-L1) that does not splice into the transmembrane domain, but instead produces a secreted form of PD-L1 that has a unique 18 amino acid tail containing a cysteine that allows it to homodimerize and more effectively inhibit lymphocyte function than monomeric soluble PD-L1. We show that recombinant secPD-L1 can dimerize and inhibit T-cell proliferation and IFN-gamma production in vitro. The secPD-L1 variant is expressed by malignant cells in vitro that also express high levels of full-length PD-L1. Transcriptomic analysis of gene expression across The Cancer Genome Atlas found the strongest association of secPD-L1 with full-length PD-L1, but also with subsets of immunologic genes, such as in myeloid-derived suppressor cells. Moreover, the splice variant is also expressed in normal tissues and within normal peripheral blood cells it is preferentially expressed in activated myeloid cells. This is the first report of a form of secreted PD-L1 that homodimerizes and is functionally active. SecPD-L1 may function as a paracrine negative immune regulator within the tumor, since secPD-L1 does not require a cell-to-cell interaction to mediate its inhibitory effect

Combination chemotherapy plus low-dose involved-field radiotherapy for early clinical stage Hodgkin's lymphoma

Purpose To present our long-term experience regarding the use of chemotherapy plus low-dose involved-field radiotherapy (IFRT) for clinical Stage I-IIA Hodgkin's lymphoma. Methods and materials We analyzed the data of 368 patients. Of these, 66 received mechlorethamine, vincristine, procarbazine, and prednisone (MOPP) and 302 received doxorubicin (or epirubicin), bleomycin, vinblastine, and dacarbazine [A(E)BVD]. Patients with complete remission or very good partial remission were scheduled for low-dose IFRT (≤3200 cGy). Results The 10-year failure-free survival (FFS) and overall survival (OS) rate was 85% and 86%, respectively. A(E)BVD-treated patients had superior 10-year FFS and OS rates compared with MOPP-treated patients (87% vs. 75%, p = 0.009; and 93% vs. 71%, p = 0.0004, respectively). Only 10 of 41 relapses had any infield (irradiated) component. Of the complete responders/very good partial responders treated with low-dose IFRT, those who received <2800 cGy had inferior FFS but similar OS as those who received 2800-3200 cGy. Adverse prognostic factors for FFS included age ≥45 years, leukocytosis ≥10 × 109/L, and extranodal extension. Secondary acute leukemia developed after MOPP with or without salvage therapy (n = 6) or after ABVD plus salvage therapy (n = 2). None of the nine secondary solid tumors developed within the RT fields. Conclusion IFRT at a dose of 2800-3000 cGy is highly effective in clinical Stage I-IIA HL patients who achieved a complete response or very good partial response with A(E)BVD. The long-term toxicity with respect to secondary malignancies appears to be acceptable. © 2004 Elsevier Inc

Molecular characterization of U937-dependent T-cell co-stimulation

U937 cells provide a co-stimulatory signal for CD3-mediated T-cell activation which is independent of the CD28/CD80/CD86 interaction. This study set out to identify which molecules contribute to this co-stimulatory activity. Monoclonal antibodies (mAb) to the known accessory molecules CD11a, CD18, CD54 and CD45, all inhibited T-cell proliferation. Although CD11a/18 mAb inhibited U937/T-cell cluster formation as well as proliferation, CD45 enhanced the size of the clusters formed, suggesting that this was not the only mechanism of inhibition. The alternative co-stimulatory pathway provided by U937 cells preferentially stimulated a response in the CD18+ T-cell population, and this reflected the reduced sensitivity of CD8+ T cells to CD28-mediated activation. Monoclonal antibodies to three molecules, CD53, CD98 and CD147, also inhibited U937-dependent T-cell proliferation. The mAb to CD98 and CD147 were inhibitory when prepulsed on to the U937 cells, suggesting an effect mediated by these molecules on the antigen-presenting cell

A role for CD45RBlow CD38+ T cells and costimulatory pathways of T-cell activation in protection of non-obese diabetic (NOD) mice from diabetes

Non-obese diabetic (NOD) mice spontaneously develop autoimmune insulin-dependent diabetes mellitus (IDDM). Infection of the animals with mycobacteria, or immunization with mycobacteria-containing adjuvant, results in permanent protection of NOD mice from diabetes and we have recently reported that the phenomenon is associated with increased numbers of interferon-γ-producing T cells, possessing increased cytotoxic activity, and also with augmented numbers of activated immunoglobulin M-positive (IgM+) B cells. Here, we have investigated whether protection of NOD mice from IDDM was associated with changes on costimulatory pathways of T and B cells, namely CD28/CTLA-4–B7 and CD40–CD40 ligand (CD40L) and we also further characterized protective T helper (Th) cells with regards to the expression of the differentiation markers CD45RB and CD38. We report that Th cells involved in diabetes vaccination of NOD mice by mycobacterial infection seem to belong to CD45RBlo CD38+ phenotype. The protective effect of Mycobacterium avium infection is also associated with increased CD40L and CTLA-4- expressing Th cells and with the generation of a CD40− IgG+ B cells. Our data are consistent with induction by mycobacterial infection of regulatory CD45RBlo CD38+ Th cells with the ability to trigger deletion or anergy of peripheral self-reactive lymphocytes, with shutting down of IgG+ B-cell response. They also implicate a role for IgG+ B cells in the autoimmune aggression of the endocrine pancreas of NOD mice

Development and validation of a clinical prediction rule for bone marrow involvement in patients with Hodgkin lymphoma

We developed a clinical prediction rule for bone marrow involvement (BMI) in Hodgkin lymphoma based on 826 patients and validated it in 654 additional patients. Independent prognostic factors for BMI were x1, B symptoms; x2, stage III/IV prior to bone marrow biopsy; x3, anemia; x4, leukocytes fewer than 6 × 109/L; x5, age 35 years or older; and x6, iliac/inguinal involvement. Each factor was graded as xi = 1, if present, or xi = 0, if absent. A simplified score Zs = 8x1 + 6x2 + 5x3 + 5x4 + 3x5 + 3x6 - 8 was assigned to each patient. The sensitivity, specificity, and positive and negative predictive value of this prediction rule was 97.8%, 51.5%, 10.6%, and 99.8%, respectively. In the validation group, they were 98.1%, 40.3%, 12.7%, and 99.6%. According to Zs value, 3 risk groups for BMI were defined: low risk (Zs < 0, 44% of patients, 0.3% risk), standard risk (Zs, 0-9; 37% of patients; 4.2% risk), and high risk (Zs ≥ 10, 20% of patients, 25.5% risk). Patients with low risk (stage IA/IIA without anemia and leukopenia; stage IA/IIA, younger than 35 years, with either anemia or leukopenia but no inguinal/iliac involvement; and stage IIIA/IVA without any of these 4 risk factors) do not need bone marrow (BM) biopsy. Patients with standard risk should be staged with unilateral biopsy, but patients with high risk may benefit from bilateral biopsy. © 2005 by The American Society of Hematology

Interleukin-15 differentially enhances the expression of interferon-γ and interleukin-4 in activated human (CD4+) T lymphocytes

In this study interleukin (IL)-15 was examined for its ability to modulate the expression of interferon-γ (IFN-γ) and IL-4 in activated human T lymphocytes. The effect of IL-15 was compared with IL-2 and IL-7, cytokines all known to use the IL-2 receptor γC chain. The results demonstrate that the extent of upregulation of IFN-γ and IL-4 mRNA was dependent on the applied cytokine (IL-2>IL-15>IL-7) and on the stimulatory signal. IFN-γ and IL-4 mRNAs were upregulated by IL-15 in concanavalin A- (twofold) and anti-CD3 plus anti-CD28- (fivefold) stimulated T lymphocytes. IFN-γ mRNA accumulation, but not IL-4 mRNA, was additively upregulated by IL-15 plus IL-7 (ninefold) in anti-CD3 stimulated T lymphocytes, and bypassed the requirement of CD28 signalling. Fluorescence-activated cell sorting (FACS) experiments demonstrated that IFN-γ mRNA was upregulated by IL-15 in both CD4+ and CD8+ T lymphocytes, whereas IL-4 mRNA accumulation predominantly occurred in CD4+ cells. Preincubation of highly purified CD4+ T lymphocytes during 7 days with IL-15 and/or IL-7, followed by activation, also showed enhanced IL-4 protein secretion, but predominantly upregulated IFN-γ protein. The net effect was a dramatically increased IFN-γ/IL-4 ratio. Taken together, IL-15 and IL-7 can act as costimulatory signals, which may favour a T helper 1 (Th1) immune response, particularly in the absence of sufficient CD28 costimulation