Scientific and technological advancements Essay Example | Topics and Well Written Essays - 750 words

Scientific and technological advancements - Essay Example The industrial revolution led to development of new economic systems in the society that greatly affected family relationships. Prior to the Industrial Revolution families worked together in the cottage system to produce their own goods for consumption. The cottage system ensured that there were strong family ties as each person had a role to play in the production process(Stearns, 2013). The Industrial Revolution, however, introduced the factory systems that required people to work for long hours away from home. With this economic system, many family members became engaged in the industrial production process. Parents had little time to spend with their children since they had to compete for the scarce jobs in industries. The Industrial Revolution also led to development and growth of towns and cities. Industries attracted more people who sought employment opportunities. These people often settled around the industries, leading to emergence of new towns and cities. Urbanization occurred at a very rapid rate leading to emergence of various social problems including housing problems, sanitation, crime, and diseases. Urbanization soon became a major challenge to the social wellbeing of the society and a focus had to shift towards addressing the social problems that emerged as a result(Stearns, 2013). The urban centers could not support the ever-increasing population due to the limited availability of resources. The Industrial Revolution led to development of capitalism as a major economic philosophy because it lee to concentration or massive wealth among factory owners. The Industrial Revolution created space for emergence of new forms of production that required workers to improve their skills in order to use machinery and factory equipment. More people moved to seek employment opportunities in the industries as well as opening up markets for the industrial products (Mielants, 2007). The few

Costimulatory activity of dendritic cells Essay Example | Topics and Well Written Essays - 750 words

Costimulatory activity of dendritic cells - Essay Example T cell activation is a highly regulated event involving complex receptor-ligand interactions, ultimately leading to downstream signaling events (Annu Rev Immunol. 2002). Optimal activation of naà ¯ve T cells requires at least two signals, antigen recognition and co-stimulation (Bretscher and Cohn 1970).The first signal requires engagement of an antigen receptor by foreign antigen. Professional antigen presenting cells (APCs) such as dentritic cells, macrophages and B-lymphocytes play a major role in this. They present different sets of antigens and serve to activate T cells at different points during immune response. These cells on encountering foreign antigens such as bacteria, engulf and destroy them. The major histocompatible cell (MHC) present in the APCs binds to a piece of this antigen and displays the antigen to the cell surface. This MHC molecule that displays the antigen is recognized by a compatible T cell receptor (TCR). Thus, these APCs communicate with a T cell (Underst anding Autoimmune Diseases. How Does the Immune System Work? 2007).For a T cell to respond to a foreign antigen on the MHC, a second signal is required. (P.Anton van der Merwe.2000).This second signal or co-stimulation is an antigen-independent signal required for sustained cell proliferation, effector/memory cell generation and prevention of energy or apoptosis. APC participation is required in the second signaling also. In addition to antigen presentation, these cells provide co stimulatory signals. ... Provide the co-stimulatory signal necessary for T cell activation. When a naive T cell binds to its specific peptide: MHC complex, the CD28 on the T cell's surface binds to the B7 molecules on the APC (Fig.1). These two signals together lead to the production of several cytokines. Fig.1: T cell activation by two-signal pathway. [Online] Available at http://www.clinsci.org. Dendritic cells are the most effective stimulators of T cell activation. They continuously express high levels of co stimulatory B7 (Fig 2). Upon recognition of infectious particles, these cells migrate through the lymphatics to the nearest lymph node. In the follicles of the lymph node, they come into close contact with the nave T cells where it begins expression of the B7 molecules. Once the T cells are activated, they will leave the lymph node and travel to the sites of inflammation. Macropohages, in the absence of infection, express low levels of MHC II and almost no co stimulators (B7). In the case of infection, however macrophages poses certain types of receptors that recognize differential carbohydrate patterns on foreign cells. They also have receptors for specific bacterial products such as lippolysaccharide endotoxin. When these molecules bind with their ligands, they stimulate the macrophages to up regulate MHC II and B& providing these cells with strong antigen presenting properties. They also start to secrete cytokines that aid in their functions. It is at this point that antigen presentation by MHC II will activate T cells. Macrophage Dendritic Cell B cell MHC-II Expression Low levels. Induced by Bacteria and/or Cytokines Always Expressed. Always Expressed. Inducible upon