Beyond Cancer: Regulation and Function of PD-L1 in Health and Immune-Related Diseases

Programmed Cell Death 1 Ligand 1 (PD-L1, CD274, B7-H1) is a transmembrane protein which is strongly involved in immune modulation, serving as checkpoint regulator. Interaction with its receptor, Programmed Cell Death Protein 1 (PD-1), induces an immune-suppressive signal, which modulates the activity of T cells and other effector cells. This mediates peripheral tolerance and contributes to tumor immune escape. PD-L1 became famous due to its deployment in cancer therapy, where blockage of PD-L1 with the help of therapeutic antagonistic antibodies achieved impressive clinical responses by reactivating effector cell functions against tumor cells. Therefore, in the past, the focus has been placed on PD-L1 expression and its function in various malignant cells, whereas its role in healthy tissue and diseases apart from cancer remained largely neglected. In this review, we summarize the function of PD-L1 in non-cancerous cells, outlining its discovery and origin, as well as its involvement in different cellular and immune-related processes. We provide an overview of transcriptional and translational regulation, and expression patterns of PD-L1 in different cells and organs, and illuminate the involvement of PD-L1 in different autoimmune diseases as well as in the context of transplantation and pregnancy

Low temperature surface conductivity of hydrogenated diamond

Conductivity and Hall experiments are performed on hydrogenated poly-CVD, atomically flat homoepitaxially grown Ib and natural type IIa diamond layers in the regime 0.34 to 400 K. For all experiments hole transport is detected with sheet resistivities at room temperature in the range 104 to 105 Ω/□. We introduce a transport model where a disorder induced tail of localized states traps holes at very low temperatures (T 70 K) the hole density is approximately constant and the hole mobility μ is increasing two orders of magnitude. In the regime 70 K 70 K is governed by the energy gap between holes trapped in the tail and the mobility edge which they can propagate. In the temperature regime T > 25 K an increasing hole mobility is detected which is attributed to transport in delocalized states at the surface

Low temperature properties of the p-type surface conductivity of diamond

Hydrogen terminated CVD poly- and monocrystalline high pressure high temperature (IIa) diamonds have been investigated by conductivity, magnetoresistivity and Hall experiments in the temperature regime 0.34–350 K. Hole transport even at lowest temperature in the valence band is detected. Below a critical temperature of 20–70 K a decreasing fraction of holes propagates with increasing mobilities of up to 400 cm2/Vs. A transport model is discussed where the hole accumulation layer is generated by diffusion of valence band electrons into surface adsorbates. The propagation of holes in this channel is dominated by electronic states, which are partially localized due to non-perfect hydrogen termination, CH dipole disorder or surface roughness and partially extended