cell recognition

• Non-specific defences are defences that do not attack specific pathogens.
• Primary defences are anything that stops disease from entering the body, including skin, blood clotting, inflammation, expulsive reflexes and mucous membranes.
• Secondary defences kill pathogens that have entered the body, for example, white blood cells (phagocytes).
• Phagocytes look for foreign antigens, which are glycoproteins on the surface of cells.
• All cells in an organism have one type of glycoprotein on all their cell surfaces.
• Phagocytes identify cells as 'self' or 'non-self' and trigger immune responses.
• Things with foreign antigens include foods, virus attachment proteins, bacteria, foreign blood, infected cells from viruses, cancer cells, and toxins.
• The cells involved in non-specific defences are phagocytes and lymphocytes.
• Phagocytes are separated into neutrophils and macrophages, which are large and have a lobed nucleus to be able to fit around pathogens when engulfing them.
• Lymphocytes are separated into t-cells and b-cells, their nucleus is very large.
• Phagocytes are released from bone marrow, they scavenge for pathogens.
• Neutrophils or 60% of white blood cells, they patrol body fluids and are released in large numbers during infection, they die after engulfing a pathogen.
• Macrophages are less than 10% of white blood cells, they are bigger than neutrophils and are found in organs.
• Macrophages are made in bone marrow and travel through the blood as monocytes, they live a long time and are very important for initiating the immune response.
• In phagocytosis, Macrophages (mast cells) release histamine during an infection to flag where the infection is occurring, this attracts neutrophils and macrophages, this is positive chemotaxis.
• Neutrophils engulf the pathogens, and opsonin marks the antigens for phagocytosis, they trap it in a vacuole.
• The vacuole fuses to a lysosome and the membrane joins together and the digestive enzymes are released onto the pathogen.
• The pathogen is hydrolysed and the neutrophil dies and pus is made.