No abstract

TRAIL, tumor necrosis factor-related apoptosis-inducing ligand, is a member of the TNF family of proteins. Tumour cells were initially found to have increased sensitivity to TRAIL compared with normal cells, raising hopes that TRAIL would prove useful as an anti-tumor agent. The production of reliable monoclonal antibodies against TRAIL and its receptors that can stain fixed specimens will allow a thorough analysis of their expression on normal and malignant tissues. Here we report the generation of monoclonal antibodies against TRAIL and its four membrane-bound receptors (TR1-4), which have been used to stain a range of normal and malignant cells, as routinely fixed specimens. Low levels of TRAIL expression were found to be limited mostly to smooth muscle in lung and spleen as well as glial cells in the cerebellum and follicular cells in the thyroid. Expression of the TRAIL decoy receptors (TR3 and 4) was not as widespread as indicated by Northern blotting, suggesting that they may be less important for the control of TRAIL cytotoxicity than previously thought. TR1 and TR2 expression increases significantly in a number of malignant tissues, but in some common malignancies their expression was low, or patchy, which may limit the therapeutic role of TRAIL. Taken together, we have a panel of monoclonal antibodies that will allow a better assessment of the normal role of TRAIL and allow assessment of biopsy material, possibly allowing the identification of tumors that may be amenable to TRAIL therapy.

CD (cluster of differentiation) Ags are cell surface molecules expressed on leukocytes and other cells relevant for the immune system. CD nomenclature has been universally adopted by the scientific community and is officially approved by the International Union of Immunological Societies and sanctioned by the World Health Organization. It provides a unified designation system for mAbs, as well as for the cell surface molecules that they recognize. This nomenclature was established by the Human Leukocyte Differentiation Antigens Workshops. In addition to defining the CD nomenclature, these workshops have been instrumental in identifying and determining the expression and function of cell surface molecules. Over the past 30 y, the data generated by the 10 Human Leukocyte Differentiation Antigens Workshops have led to the characterization and formal designation of more than 400 molecules. CD molecules are commonly used as cell markers, allowing the identification and isolation of leukocyte populations, subsets, and differentiation stages. mAbs against these molecules have proven to be essential for biomedical research and diagnosis, as well as in biotechnology. More recently, they have been recognized as invaluable tools for the treatment of several malignancies and autoimmune diseases. In this article, we describe how the CD nomenclature was established, present the official updated list of CD molecules, and provide a rationale for their usefulness in the 21st century.

No abstract

T lymphocytes (T cells) express T-cell receptor (TCR) molecules on their surface that can recognize peptides (p) derived from antigenic proteins bound to products of the major histocompatibility complex (MHC) genes. The pMHC molecules are expressed on the surface of antigen-presenting cells, such as dendritic cells (DCs). T cells first encounter antigen on DCs in lymph nodes (LN). Intravital microscopy experiments show that upon entering the LN containing antigen, CD8؉ T cells first move rapidly. After a few hours, they stop and make extended contacts with DCs. The factors that determine when and how this transition occurs are not well understood. We report results from computer simulations that suggest that the duration of phase one is related to the low probability of productive interactions between T cells and DCs. This is demonstrated by our finding that the antigen dose and type determine when such a transition occurs. These results are in agreement with experimental observations. TCR-pMHC binding characteristics and the antigen dose determine the time required for a productive T-cell-DC encounter (resulting in sustained contact). We find that the ratio of this time scale and the half-life of the pMHC complex itself provide a consolidated measure of antigen quantity and type. Results obtained upon varying different measures of antigen quantity and type fall on one curve when graphed against this ratio of time scales. Thus, we provide a mechanism for how the effects of varying one set of parameters are influenced by other prevailing conditions. This understanding should help guide future experimentation.Recent multiphoton and confocal microscopy experiments have produced vivid images of the migration of T cells in lymphoid tissues during antigen recognition (2, 6-8, 11, 23, 30, 32-34, 37, 38, 40, 43, 47). For both CD4 and CD8 T cells, the motility characteristics change with time. Initially, T cells move quite rapidly upon entering the lymph node (LN). In the presence of cognate antigen, after a few hours, antigen-specific T cells slow down and make stable contacts with dendritic cells (DCs) presenting cognate antigen (6,23,30,32,33,37,38,40). For CD8 T cells, these two stages of different T-cell motility have been labeled "phase one" and "phase two" behavior (30). It seems reasonable to assume that phase one corresponds to a period during which T cells "hunt" for antigen, whereas phase two is a period of time required for signaling processes that result in a full commitment to activation (30,33). An important open question is which factors determine the time required for the transition from phase one to phase two. This is important, since this decision predicates T-cell activation and the initiation of an immune response.Several hypotheses could be considered to address this question. One is that T cells may go through such motility changes by default (30). This hypothesis implies that all antigen-specific T cells in the LN would transition into phase two synchronously and that the time at which this happe...