Effect of human recombinant Endostatin protein on human angiogenesis

Tumor growth and metastasis are dependent on the development of new blood vessels. Inhibitors of new vessel growth have been widely investigated as anti-tumor agents. Endostatin, a 20 kDa C-terminal fragment of collagen XVIII inhibits endothelial cell proliferation, induces endothelial cell apoptosis, and can both inhibit and reverse tumor growth in mice. However, human recombinant endostatin has had limited testing against human tissue targets. To investigate the effect of human endostatin on a human vessel target over a broad range of concentrations (10^–12–10^–4 M), human placental vein disks were grown for a period of 2 weeks in a 0.3% fibrin clot overlayed with growth medium. Disks from five individual placentas were tested. For each placenta utilized, a control (medium and 20% fetal bovine serum [FBS]) group and a group treated with heparin (300 g/ml) and hydrocortisone 21-phosphate (350 g/ml) (heparin-steroid) at a dose known to inhibit angiogenesis were included. Endostatin was tested at concentrations of 10^–12–10^–4 M in medium containing 20% FBS. The rate of initiation and the angiogenic growth index (on a visually graded semi-quantitative scale of 0–16) were determined for all experimental conditions. Endostatin inhibited angiogenesis in our model only in high concentrations. At 10^–5 M, endostatin did not alter the percent of wells that initiated an angiogenic response, but significantly inhibited subsequent vessel growth. At 10^–4 M, endostatin was able to inhibit both initiation and subsequent new vessel growth. Human endostatin can inhibit the initiation of a human angiogenic response and inhibit the subsequent proliferation of human neovessels when used at high doses in a continuous exposure model.     

Human Leukocyte Antigens and Cellular Immune Responses to Anthrax Vaccine Adsorbed

Interindividual variations in vaccine-induced immune responses are in part due to host genetic polymorphisms in the human leukocyte antigen (HLA) and other gene families. This study examined associations between HLA genotypes, haplotypes, and homozygosity and protective antigen (PA)-specific cellular immune responses in healthy subjects following immunization with Anthrax Vaccine Adsorbed (AVA). While limited associations were observed between individual HLA alleles or haplotypes and variable lymphocyte proliferative (LP) responses to AVA, analyses of homozygosity supported the hypothesis of a “heterozygote advantage.” Individuals who were homozygous for any HLA locus demonstrated significantly lower PA-specific LP than subjects who were heterozygous at all eight loci (median stimulation indices [SI], 1.84 versus 2.95, P = 0.009). Similarly, we found that class I (HLA-A) and class II (HLA-DQA1 and HLA-DQB1) homozygosity was significantly associated with an overall decrease in LP compared with heterozygosity at those three loci. Specifically, individuals who were homozygous at these loci had significantly lower PA-specific LP than subjects heterozygous for HLA-A (median SI, 1.48 versus 2.13, P = 0.005), HLA-DQA1 (median SI, 1.75 versus 2.11, P = 0.007), and HLA-DQB1 (median SI, 1.48 versus 2.13, P = 0.002) loci, respectively. Finally, homozygosity at an increasing number (≥4) of HLA loci was significantly correlated with a reduction in LP response (P < 0.001) in a dose-dependent manner. Additional studies are needed to reproduce these findings and determine whether HLA-heterozygous individuals generate stronger cellular immune response to other virulence factors (Bacillus anthracis LF and EF) than HLA-homozygous subjects.     

Multiple paths to loss of anergy and gain of autoimmunity

B cells and autoimmunity: cells of the immune system have the capacity to recognize/neutralize a myriad array of disease-causing pathogens, while simultaneously minimizing damage to self tissue. Obvious breakdowns in this ability to distinguish between self and non-self are evident in multiple forms of autoimmune disease, where B and T cells mount damaging attacks on cells and organs. B cells may directly damage tissue by producing pathogenic antibodies that bind self antigen, fix complement or form immune complexes. Recent evidence also suggests B cells indirectly induce autoimmunity by concentrating low avidity self antigen through the B cell receptor and presenting self-peptides to autoreactive T cells. B cells may also initiate autoimmunity when provided sufficient help from autoreactive T cells that have escaped deletion in the thymus. Here, we will review the role of anergy in maintenance of tolerance and how alterations in the normal balance of positive and negative signals may contribute to the development of autoimmune disease in mouse models and humans.     

Potential Mechanisms of Interferon-α Induced Autoimmunity

The type I interferons (IFN) are cytokines encoded by a multigene family comprising 13 closely related IFN-A genes, and a single IFN-B gene. These factors are rapidly induced upon viral infection, and have pleiotropic effects. Historically, the induction of a cell-autonomous state of antiviral resistance, the inhibition of cell growth, and the regulation of apoptosis were appreciated first. More recently, it became generally accepted that they can regulate immune effector functions. This latter feature led them to be reconsidered as signals linking innate and adaptive immunity, and potentially orchestrating autoimmunity associated with viral infection and IFN-α therapy. Common to almost all autoimmune diseases is their polygenic inheritance, incomplete penetrance, and evidence for the role of environmental factors, particularly viral infection. In addition, they are characterized by increased numbers of circulating autoreactive T- and B-cells. Endogenously produced or therapeutically applied IFN-α can tilt the usually tightly controlled balance towards activation of these autoreactive cells via a vast array of mechanisms. The genetic susceptibility factors determine which type of autoimmunity will develop. IFN-α induces numerous target genes in antigen presenting cells (APC), such that APC are stimulated and enhance humoral autoimmunity, promote isotype switching, and potently activate autoreactive T cells. Moreover, IFN-α can synergistically amplify T cell autoreactivity by directly promoting T cell activation and keeping activated T cells alive. In essence, type I IFNs may constitute one example of genes that have been conserved because they confer dominant disease resistance, but at the same time they can trigger autoimmunity in genetically susceptible individuals.