The Role of Blood in Providing Immunity Against Disease.
Introduction
Blood plays a vital role in the immune system; it has four main components. Plasma is the liquid part that carries carbon dioxide and waste. Red blood cells contain the haemoglobin which carries oxygen. White blood cells play an important role. They produce antibodies and destroy harmful microorganisms that our bodies do not recognise. Lastly we have platelets; these clump together to form blood clots to stop us from bleeding. There are a number of ways the body fights infection and are referred to as the first line of defence. These include the skin itself, scabbing/clotting, cilia and mucus. These are all an initial barrier. The second line of defence will be noticed by swelling. This is a protective response brought by the white blood cells. These and the injured cells release histamine. This increases blood flow to infected area. The increase in fluid causes swelling and the increase of blood causes redness and heat. [See class notes]
Pathogen
A pathogen is a microorganism that can cause disease. Pathogens include bacterium, i.e. Bacterial meningitis virus i.e. hepatitis or fungus i.e. athletes foot [Iaff.org, (2015). ] White blood cells can ingest and destroy the pathogen. They produce antibodies to destroy pathogens. One of the most common ways pathogens are spread is through personal contact. The common cold is usually spread through saliva and the HIV virus is spread during intercourse or sharing needles.
Phagocytes
Phagocytosis is the ingestion of particles by cells. A phagocyte is a type of cell found within the body capable of engulfing and absorbing bacteria and other small cells and particles. The immune response is initiated by an activation phase. This is where the phagocyte engulfs and digests the antigens through a process called phagocytosis. [Gilbert, Joanna (March 2005)]. Phagocytes use phagocytosis to clear away the antigen and antibody in an immune response. Two types of phagocytes are Macrophages and Neutrophiles. The Neutrophiles are found in the blood and Macrophages are found in the tissue. They are both made in the bone marrow. [See class notes].
T-Cells
T cells are a type of white blood cell that works with macrophages. Unlike macrophages that can attack any cell or virus, each T cell can fight only one type of virus. They are a type of white blood cell that circulates round our bodies scanning for abnormalities and infections. They mature in the thymus gland and remain in the lymph tissue. They belong to a group of white blood cells called lymphocytes. They are highly specialised cells. [T Cell Modulation Group (2009)] The main role of T cells is to fight infection. There are different types of T cells that act in different ways to identify attack and destroy infectious agents. [Mallick, I. (2014).] T cells contribute to the immune defences in two different ways: Some direct and regulate immune responses whereas others directly fight of the infected or cancerous cells. [ U.S Department of health and human services (2008).] They respond to antigens on the surface of the body cells which has been invaded by pathogens. This recognition depends on specific receptors on the surface of the T cell. These are known as T cell receptors and bind to their specific antigen. [see class notes] The killer T cell is specialized in attacking cells of the body infected by viruses and sometimes also bacteria. It can also attack cancer cells.[Nobelprize.org, (2014). ]
B-Cells
B cells are a type of lymphocyte. They work by secreting substances called antibodies into the bodies fluids. Antibodies attack antigens circulating in the blood stream. Antigens identify a molecule as being foreign. The cells are produced and formed in the bone marrow. [See class notes]. B cells can recognise millions of different antigens. B cells can recognise antigens that have never entered the body before, and even man-made molecules that don't exist in nature.