CZZ101 revision baby pt.4 😃

• The primary types of phagocytosis using five processes include; chemotaxis, adherence, ingestion, digestion, killing
• chemotaxis is the movement of a phagocyte to the site of damage due to the chemical stimulus
• adherence is attachment of the phagocyte to the microbe
• ingestion is the formtion of the phagolysosome
• digestion uses lysosomes to degrade microbial material
• killing of bacteria is the elimination of the mcirobe
• cells of the innate immune system include; dendritic cells, mast cells, basophils, eosinophils, monocytes/macrophages, neutrophils, and natural killer cells.
• eosinophils control parasitic infections
• mast cells are involved in inflammation and tissue healing
• natural killer cells, can kill cancer cells, that do not express immune related molecules
• MHC are used to signal to the immune system when a cell is infected
• Natural killr cells use perforin which creates perforations in the cell membrane in order to allow granzymes to enter the cell and cause apoptosis (cell death
• the innate immune system, is quick to respond, is non-specific and is local
• The adaptive immune response is specific, it has memory, can take up to days to activate
• t cell receptors bind to antigens found on abnormal cells and cancer cells, this interaction triggers the t-lymphocytes and they help the body fight off infection
• BCR receptors interact with foreign materials the mediate B cell activation and secrete antibodies.
• Individual B cells are all different from each other
• T cells come from the thymus
• clonal replication produces genetically different T and B cells which are extremely specific
• once the replication of B and T cells occurs they migrate to lymph nodes which is where they wait until their specific antigen is detected
• Dendritic cells can engulf bacteria, and present it to the B and T cells, they start in lymphatic vessels and move into the lymph node where they present the bacteria
• Dendritic cells move into the cell with parts of the ingested bacteria (MHC). T cells are unable to detect the bacteria without the antigen-presenting cell (dendritic cells). Only the specific T-cells can be destroyed.
• B cells in the lymph nodes are able to recognise specific antigens, without assistance from the antign presenting cells. Specific b cells can bind and destroy pathogens.
• Once the B and T cells have recognised cells, they will replicate like crazy
• Once the B and T lymphocytes replicate they will replicate and have identical receptors to the cells that produced them. they need an army to fight an infection
• Some of the identical B and T lymphocytes which have been replicated, will become effector cells which means they will deal with the infection now, while others act as memory cells. The memory cells will wait for the next time the same infection is encountered and now how to respond appropriately
• During the last phase of clonal selection The B cells pump out antibodies which will help to fight the invader. The T cells may remain in the lymph nodes.
• Clonal selection


  1. T and B lymphocytes move from bone marrow to thymus to lymph nodes

  2. Lymphocyte waits for matching receptor

  3. Lymphocyte activated when bacterium comes along

  4. Activated lymphocyte replicates through mitosis to form genetically identical replications

  5. Replicated effector cells remove bacteria, other cells become memory cells
• T and B lymphocytes


  • Genetically different
• Lymphocyte is initially paired with

  T or B cell is activated
• Effector cells


  Replicated cells involved in removal of bacteria
• Memory cells


  Replicated cells that can recognize and respond quickly to bacteria next time it is encountered
• Antigen-presenting cells and B-lymphocytes find bacteria and ingest it, breaking it into small pieces, they then display them on a receptor on the outside of the cell this is known as MHC-II.
• All nucleated cells in the human body have MHC I molecules on their surface.
• dendritic cells and B-lymphocytes have both MHC I and MHC II receptors
• MHC I is on every cell that has a nucleus
• red blood cells don't have nucleus
• helper t cells bind to MHC class II molecules on the surface of antigen presenting cells
• MHC I attracts cytotoxic T-cells
• when it finds a cell with the correct MHC I. and decides that it needs to be destroyed, it divides and differentiates into memory cells and effector T-cells (killing)