immuno test 1

• Immune cell types include myeloid and lymphoid cells.
• Pathogens are infectious agents that cause disease, mostly viruses, bacteria, protists and fungi.
• The immune system is the body’s defense system that detects and destroys invading pathogens.
• Immune receptors will be the subject of the next PowerPoint.
• Cytotoxic T cells have receptors (antigen receptors) that enable them to detect and bind the infected cells while sparing uninfected cells.
• A single cytotoxic T cell can move on to a new target and kill a series of target cells in succession.
• The function of cytotoxic T cells is to kill infected cells.
• The advantages of the immune system are that it can recognize a broad range of pathogens and respond immediately.
• The disadvantages of the immune system are that its defense mechanisms are non-specific and often kill normal healthy cells as well as pathogens, which contributes to symptoms of disease.
• The innate immune response is rapid but non-specific.
• The advantages of the innate immune response are its high specificity and its ability to destroy the pathogen.
• The disadvantages of the innate immune response are that it takes time to develop and we would die of the infection if we had no innate immunity as a stop-gap.
• The adaptive (acquired) immune response is highly specific but takes time to develop.
• No immune system cells are called white blood cells (leukocytes) and they are the immune cells that make up the immune system.
• Red blood cells (erythrocytes) transport oxygen around the body and are not involved in immunity.
• Platelets are involved in blood clotting.
• White blood cells are called leukocytes and they are the immune cells that make up the immune system.
• Leukocytes trace their ancestry back to hematopoietic stem cells in the bone marrow, but they are divided into two distinct lineages: myeloid cells are primarily involved in the innate immune response; lymphoid cells, also called lymphocytes, are primarily involved in the adaptive immune response.
• Granulocytes, a subset of myeloid cells, are 40-75% of leukocytes in blood and are the first responders to an infection, moving into infected tissue, killing pathogens and removing them by phagocytosis.
• Polymorphonuclear leukocytes (PMN or PML) are 1-6% of leukocytes in blood and are involved in defense against parasites and allergies.
• Mast cells are distinct granulocytes that after production in bone marrow, leave the blood and take up residence in tissue where they function as sentinels to detect infection.
• Mast cells are mononuclear cells (they have a round nucleus), not polymorphonuclear leukocytes.
• Monocytes/macrophages circulate in the blood as immature mononuclear cells called monocytes and migrate into tissues to develop into their mature form, called macrophages.
• Macrophages have diverse functions, many of which are resident in tissues and play important roles in normal tissue homeostasis by scavenging and removing debris and dead cells.
• Macrophages also play important roles in innate immune responses.
• Macrophages that are resident in tissues can help to detect infections.
• Phagocytosis activates a respiratory burst by NADPH oxidase that produces reactive oxygen species (ROS) that help to kill pathogens.
• A response that depends on the constitutive secretory pathway is significantly delayed: it takes hours for new protein synthesis and transport of the proteins through the RER and Golgi.
• Neutrophils and macrophages use degranulation to release the contents of their secretory granules, which include antimicrobial enzymes and antimicrobial peptides.
• Monocytes that circulate in blood can respond to infections by migrating into tissue (like neutrophils), where they mature into macrophages that fight the infection.
• The contents of neutrophil secretory granules include antimicrobial enzymes such as lysozyme and elastase that digest microbes, and antimicrobial peptides such as defensins that penetrate microbial membranes and disrupt their integrity.
• Neutrophils die by apoptosis and are removed by macrophages.
• Granulocytes function more like hand grenades than fixed artillery.
• Neutrophils and macrophages are phagocytes: they internalize pathogens such as bacteria by phagocytosis (a type of endocytosis) into membrane organelles called endosomes or “phagosomes.”
• Granulocytes have a short life-span: they quickly deplete their granules and then die.
• The pathogens are eventually digested in lysosomes (“phagolysosomes”).
• Secretory granules are made by the regulated secretory pathway: the proteins pass through the RER and Golgi as before, but then the pathway is stopped (it is not continuous).
• Neutrophils and macrophages use phagocytosis to eat and digest pathogens in lysosomes.
• Secretory granules can package other molecules besides proteins: some of these molecules are made in the cytoplasm and then transported into the secretory granules for storage.
• Secretory granules store pre-made components that can be released from cells by degranulation (exocytosis) immediately after cell stimulation.