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Programmed death-ligand 1 (PD-L1) expression on tumor cells is essential for T cell impairment, and PD-L1 blockade therapy has shown unprecedented durable responses in several clinical studies. Although higher expression of PD-L1 on tumor cells is associated with a better immune response after Ab blockade, some PD-L1- negative patients also respond to this therapy. In the current study, we explored whether PD-L1 on tumor or host cells was essential for anti-PD-L1-mediated therapy in 2 different murine tumor models. Using real-time imaging in whole tumor tissues, we found that anti-PD-L1 Ab accumulates in tumor tissues, regardless of the status of PD-L1 expression on tumor cells. We further observed that, while PD-L1 on tumor cells was largely dispensable for the response to checkpoint blockade, PD-L1 in host myeloid cells was essential for this response. Additionally, PD-L1 signaling in defined antigen-presenting cells (APCs) negatively regulated and inhibited T cell activation. PD-L1 blockade inside tumors was not sufficient to mediate regression, as limiting T cell trafficking reduced the efficacy of the blockade. Together, these findings demonstrate that PD-L1 expressed in APCs, rather than on tumor cells, plays an essential role in checkpoint blockade therapy, providing an insight into the mechanisms of this therapy., Introduction The programmed death-1 receptor/programmed death-ligand 1 (PD-1/PD-L1) signaling pathway plays an important role in tumor evasion of host immune responses (1). Recent clinical trials with PD-1/PD-L1 blockade therapy have [...]

Context.--New molecular diagnostic tests are attractive because of the potential they hold for improving diagnostics in microbiology. The value of these tests, which is often assumed, should be investigated to determine the best use of these potentially powerful tools. Objective.--To investigate the usefulness of broad-range polymerase chain reaction (PCR), followed by sequencing, in mycobacterial infections. Design.--We reviewed the test performance of acid-fast bacilli (AFB) PCR and traditional diagnostic methods (histopathology, AFB smear, and culture). We assessed the diagnostic effect and cost of the unrestricted ordering of broad-range PCR for the detection and identification of mycobacteria in clinical specimens. Results.--The AFB PCR was less sensitive than culture and histopathology and was less specific than culture, AFB smear, and histopathology. During 18 months, $93 063 was spent on 183 patient specimens for broad-range PCR and DNA sequencing for mycobacteria to confirm one culture-proven Mycobacterium tuberculosis infection that was also known to be positive by AFB smear and histopathology. In this cohort, there was a false-negative AFB PCR for M tuberculosis and a false-positive AFB PCR for Mycobacterium lentiflavum. Conclusion.--Testing of AFB smear-negative specimens from patients without an inflammatory response supportive of a mycobacterial infection is costly and has not been proven to improve patient care. Traditional diagnostics (histopathology, AFB smear, and culture) should remain the primary methods for the detection of mycobacteria in clinical specimens. (Arch Pathol Lab Med. 2015; 139:1020-1023; doi: 10.5858/arpa.2013-0705-OA), Selection of the optimum tests for a specimen becomes more challenging as newer testing methods become increasingly available for the detection of microorganisms. Polymerase chain reaction (PCR)-based methods for microorganism [...]

Immunotherapies aimed at enhancing natural or endogenous antitumor T-cell immunity in patients affected by advanced malignancies are currently being implemented in the clinic with promising results. In order to optimize therapeutic protocols and monitor the effectiveness of such therapies, reliable biomarkers are needed. We used CD11a, an integrin that is upregulated on the surface of effector and memory CD8+ T cells, and PD-1, an immunoregulatory receptor expressed by activated T cells, as biomarkers to identify, quantify and monitor endogenous tumor-reactive cytotoxic T lymphocytes (CTLs) in two mouse tumor models and in the peripheral blood of 12 patients affected by Stage IV melanoma. High expression levels of CD11a and PD-1 were detected among CD8+ T cells residing within primary and metastatic murine tumor sites, as well as in spontaneous murine breast cancer tissues. In the peripheral blood of melanoma patients, tumor antigen-specific CD8+ T cells were associated with a population of CD11ahigh CD8+ T cells that co-expressed high levels of PD-1. Healthy donors exhibited a comparatively much lower frequency of such PD-1+CD11ahighCD8+ T cells. Phenotypic analyses demonstrated that CD11ahighCD8+ T cells are proliferating (Ki67+) and activated (CD62L-CD69+). Increased CD11ahighCD8+ T cells and delayed tumor growth were observed in PD-1 deficient mice, suggesting that the antitumor effector functions of CD8+ T cells is compromised by an elevated expression of PD-1. The CD11ahighCD8+ T-cell population expresses high levels of PD-1 and presumably constitutes the cellular target of PD-1 blockade therapy. The expression level of CD11a and PD-1 by CD8+ T cells may therefore represent a novel biomarker to identify and monitor endogenous tumor-reactive CTLs. This may not only provide an immunological readout for evaluating the efficacy of immunotherapy but also contribute to the selection of cancer patients who are likely to benefit from anti-PD-1 therapy. [ABSTRACT FROM AUTHOR]

B7-H1 (aka PD-L1) blocking antibodies have been used in treatment of human cancers through blocking B7-H1 expressed by tumor cells; however, their impact on B7-H1 expressing tumor-reactive CD8+ T cells is still unknown. Here, we report that tumor-reactive CD8+ T cells expressing B7-H1 are functional effector cells. In contrast to normal B7-H1 blocking antibody, B7-H1 antibodies capable of activating p38 MAPK lose their antitumor activity by deleting B7-H1+ tumor-reactive CD8+ T cells via p38 MAPK pathway. B7-H1 deficiency or engagement with certain antibody results in more activation of p38 MAPK that leads to T cell apoptosis. DNA-PKcs is a new intracellular partner of B7-H1 in the cytoplasm of activated CD8+ T cells. B7-H1 suppresses p38 MAPK activation by sequestering DNA-PKcs in order to preserve T cell survival. Our findings provide a new mechanism of action of B7-H1 in T cells and have clinical implications in cancer immunotherapy when anti-B7-H1 (PD-L1) antibody is applied. [ABSTRACT FROM AUTHOR]

B7-H1 (aka PD-L1) blocking antibodies have been used in treatment of human cancers through blocking B7-H1 expressed by tumor cells; however, their impact on B7-H1 expressing tumor-reactive CD8 + T cells is still unknown. Here, we report that tumor-reactive CD8 + T cells expressing B7-H1 are functional effector cells. In contrast to normal B7-H1 blocking antibody, B7-H1 antibodies capable of activating p38 MAPK lose their antitumor activity by deleting B7-H1 + tumor-reactive CD8 + T cells via p38 MAPK pathway. B7-H1 deficiency or engagement with certain antibody results in more activation of p38 MAPK that leads to T cell apoptosis. DNA-PKcs is a new intracellular partner of B7-H1 in the cytoplasm of activated CD8 + T cells. B7-H1 suppresses p38 MAPK activation by sequestering DNA-PKcs in order to preserve T cell survival. Our findings provide a new mechanism of action of B7-H1 in T cells and have clinical implications in cancer immunotherapy when anti-B7-H1 (PD-L1) antibody is applied.

Immunotherapies aimed at enhancing natural or endogenous antitumor T-cell immunity in patients affected by advanced malignancies are currently being implemented in the clinic with promising results. In order to optimize therapeutic protocols and monitor the effectiveness of such therapies, reliable biomarkers are needed. We used CD11a, an integrin that is upregulated on the surface of effector and memory CD8 + T cells, and PD-1, an immunoregulatory receptor expressed by activated T cells, as biomarkers to identify, quantify and monitor endogenous tumor-reactive cytotoxic T lymphocytes (CTLs) in two mouse tumor models and in the peripheral blood of 12 patients affected by Stage IV melanoma. High expression levels of CD11a and PD-1 were detected among CD8 + T cells residing within primary and metastatic murine tumor sites, as well as in spontaneous murine breast cancer tissues. In the peripheral blood of melanoma patients, tumor antigen-specific CD8 + T cells were associated with a population of CD11a high CD8 + T cells that co-expressed high levels of PD-1. Healthy donors exhibited a comparatively much lower frequency of such PD-1 + CD11a high CD8 + T cells. Phenotypic analyses demonstrated that CD11a high CD8 + T cells are proliferating (Ki67 + ) and activated (CD62L - CD69 + ). Increased CD11a high CD8 + T cells and delayed tumor growth were observed in PD-1 deficient mice, suggesting that the antitumor effector functions of CD8 + T cells is compromised by an elevated expression of PD-1. The CD11a high CD8 + T-cell population expresses high levels of PD-1 and presumably constitutes the cellular target of PD-1 blockade therapy. The expression level of CD11a and PD-1 by CD8 + T cells may therefore represent a novel biomarker to identify and monitor endogenous tumor-reactive CTLs. This may not only provide an immunological readout for evaluating the efficacy of immunotherapy but also contribute to the selection of cancer patients who are likely to benefit from anti-PD-1 therapy.

Protective T‑cell immunity against cancer and infections is dependent on the generation of a durable effector and memory T‑cell pool. Studies from cancer and chronic infections reveal that B7-H1 (PD-L1) engagement with its receptor PD-1 promotes apoptosis of effector T cells. It is not clear how B7-H1 regulates T‑cell apoptosis and the subsequent impact of B7-H1 on the generation of memory T cells. In immunized B7-H1-deficient mice, we detected an increased expansion of effector CD8(+) T cells and a delayed T‑cell contraction followed by the emergence of a protective CD8(+) T‑cell memory capable of completely rejecting tumor metastases in the lung. Intracellular staining revealed that antigen-primed CD8(+) T cells in B7-H1-deficient mice express lower levels of the pro-apoptotic molecule Bim. The engagement of activated CD8(+) T cells by a plate-bound B7-H1 fusion protein led to the upregulation of Bim and increased cell death. Assays based on blocking antibodies determined that both PD-1 and CD80 are involved in the B7-H1-mediated regulation of Bim in activated CD8(+) T cells. Our results suggest that B7-H1 may negatively regulate CD8(+) T‑cell memory by enhancing the depletion of effector CD8(+) T cells through the upregulation of Bim. Our findings may provide a new strategy for targeting B7-H1 signaling in effector CD8(+) T cells to achieve protective antitumor memory responses.