phagocytosis

• phagocytes

  -non- specific

  -macrophages and neutrophils

  -engulf and digest foreign particles in phagocytosis
• macrophages

  -larger and live longer than neutrophils

  -made in bone marrow

  -travel in blood until they settle in lymph nodes

  -histamine- leaky capillaries- more tissue fluid in lymph nodes- delivers pathogens to macrophages

  -antigen- presenting cells
• neutrophils

  -larger than erythrocytes

  -short lived and often die after engulfing pathogen

  -account for 60% of white blood cells

  -tri- lobed nucleus- flexibility

  -made in bone marrow

  -move out of capillaries- fenestrations

  -attracted to infected cells by histamine released from the infected cells
• adaptations of phagocytes

  -need lots of mitochondria

  -ribosomes and rough ER- globular proteins

  -cytoskeleton well developed

  -extra lysosomes- digestive enzymes
• phagosome

  vacuole inside a phagocyte which creates an infolding of plasma membrane to engulf a foreign particles- held inside phagosome
• chemotaxis

  movement of cells or organisms towards or away polar chemicals
• antigen presenting cells

  -antigens are proteins or glycoproteins on surface of cells- identify cells as self or non-self/ foreign

  -phagocytes may display the pathogen's antigens in their own plasma membrane= antigen presentation

  -MHC protein prevents APC from being attacked and mistaken for a foreign cell
• agglunation

  -antibody- several sites that can bind to an antigen

  -bacterium with antigens on surface

  -antibody makes bacteria clump together- agglunated bacteria don't move around as much and are easily engulfed by phagocytes
• neutralisation

  -antibody binds to toxins released by pathogen

  -toxins released by pathogens can be neutralised- antibodies and toxins bind to form toxin- antibody complexes

  -too large to enter cells and cause damage
• neutralising

  -blocks receptors and binding sites

  -also attack flagella- prevent movement

  -sometimes create holes in cell walls- causes pathogens to burst- lysis
• opsonisation

  -antibodies and opsonins bind to antigen and act as a binding site for phagocytes

  -some opsonins are non- specific and bind to any molecules

  -some opsonins are specific- often leads to neutralisation
• antibodies

  -globular proteins (soluble)

  -blood plasma and tissue fluid and lymph during an infection

  -made by plasma cells which are a type of b-lymphocyte

  -specific to 1 particular antigen

  -extracellular proteins- exocytosis

  -immunoglobulins

  -quartenary structure- 4 sub units
• quaternary structure of antibodies

  -2 x light chains

  -2 x heavy chains

  -held together by disulphide bonds

  -variable region- unique to each antibody- binds to antigen on pathogen

  -constant region- binding to site of phagocytes

  -hinge region- flexibility- bind to more than one antigen at once- efficient- more pathogens destroyed
• 4 roles of antibodies

  -neutralisation

  -opsonisation

  -neutralise toxins/ act as anti-toxins

  -agglutination