Immune system Flashcards
What are leukocytes and what role do they play in the immune system?
Leukocytes are the only complete cells in the blood, making up less than 1% of blood volume.
- protect the body against bacteria, viruses, parasites, toxins, and tumor cells
What is leukocytosis, and what causes it?
- WBC count exceeds 11,000/μl, which is often a response to bacterial or viral infections.
- can double within hours as part of the defense mechanisms
How do leukocytes move?
- can leave the bloodstream to mount immune and inflammatory responses
- amoeboid motion and are attracted to areas of infection via chemotaxis.
What are the two main categories of leukocytes, and what distinguishes them?
- Granulocytes: These have visible cytoplasmic granules and include neutrophils, eosinophils, and basophils.
- Agranulocytes: These lack visible granules and include lymphocytes and monocytes.
What is leukopoiesis and how is it regulated?
producing leukocytes in the bone marrow, which is hormonally regulated by interleukins and colony-stimulating factors
- granulocytes are stored in the bone marrow, and their lifespan ranges from 0.25 days to 9 days, with most dying in the line of duty
What are the specific types of granulocytes and their functions?
- Neutrophils: The most common type (50%+ of leukocytes), they are phagocytic and protect the body from bacterial infections.
- Eosinophils: Represent 2-4% of leukocytes, and are involved in fighting parasitic infections and modulating allergic responses (e.g., asthma).
- Basophils: The rarest WBCs (0.5%), their granules release histamine to promote vasodilation and attract other immune cells.
What are the main leukocyte disorders, and how do they impact the body?
- Leukemia: A cancer of WBCs where cells remain unspecialized and mitotic. This can cause severe anemia, clotting problems, and infections. The WBCs are numerous but non-functional.
- Infectious Mononucleosis: Caused by Epstein-Barr virus, leading to an increased number of abnormally-shaped lymphocytes.
- Leukopenia: A condition where the WBC count is abnormally low, often due to drugs like glucocorticoids or chemotherapy.
What are the specific types of agranulocytes and their roles in immunity?
- Lymphocytes: They are the second most common type of WBC. T cells target virus-infected and tumor cells, while B cells produce antibodies to fight infections.
- Monocytes: The largest WBCs, which differentiate into macrophages in tissues and play a key role in phagocytosis during chronic infections like tuberculosis.
What are innate defenses in the immune system, and how do they work?
Innate defenses are nonspecific immune responses that protect the body against a wide range of pathogens and abnormalities without targeting a specific pathogen.
- responses triggered by pathogen-associated molecular patterns (PAMPs) or damage-associated molecular patterns (DAMPs) from the body’s own cells.
What are PAMPs and DAMPs, and how do they alert the immune system?
- PAMPs: Pathogen-associated molecular patterns are molecules associated with pathogens (e.g., bacterial cell walls) that are recognized by the immune system.
- DAMPs: Damage-associated molecular patterns are molecules from the body’s own cells, such as DNA outside the nucleus, that signal tissue damage. These patterns alert the innate immune system to potential threats without needing to recognize specific pathogens.
How do skin and mucous membranes contribute to the body’s first line of defense?
act as physical barriers to pathogens
secrete chemicals like:
- acidic secretions
- lysozyme (an enzyme that breaks down bacterial cell walls)
- mucin (which traps microorganisms)
- defensins (antimicrobial peptides)
What chemicals are involved in inflammation, and how do they contribute to immune defense?
histamine, kinins, prostaglandins, and complement
- released by: damaged tissues, macrophages, and lymphocytes
- increase blood flow, make capillaries more permeable, attract immune cells to the site, and help initiate repair.
What are the key features and purposes of inflammation in the immune response?
Inflammation is a response to injury or infection, marked by redness, heat, swelling, and pain.
- prevents the spread of microorganisms
- removes debris
- initiates tissue repair
- activates the adaptive immune system to fight the infection more specifically
What is interferon, and how does it function?
a protein secreted by virus-infected cells
- diffuses to nearby non-infected cells and blocks protein synthesis, while also degrading viral RNA.
Is interferon virus-specific?
NO, works against a wide range of viruses, not just one particular type
How does interferon activate the immune system?
activate macrophages and mobilize natural killer cells, contributing to immune responses and also having some anti-cancer effects.
What is the complement system?
a group of at least 20 plasma proteins that circulate in an inactive state and are activated as part of the immune response.
What is the role of C3b in the complement system?
functions as an opsonin, meaning it enhances the ability of phagocytes (like macrophages) to recognize, engulf, and destroy pathogens.
What happens once the complement system is activated?
the components of the complement system amplify all aspects of the inflammatory process, helping to fight infections.
How does fever contribute to the immune response?
caused by pyrogens released by leukocytes and macrophages in response to bacterial or foreign substances, resetting the body’s thermostat.
What are pyrogens and how do they affect the body?
are substances released by leukocytes and macrophages in response to infection. They cause the body’s thermostat to reset, leading to fever.
Why is a moderate fever helpful?
Moderate fever speeds up the metabolic rate and causes the liver and spleen to sequester iron and zinc, making them less available to pathogens, which helps limit their growth.
Why is high fever dangerous?
it can damage tissues and organs, potentially leading to serious complications.
Are natural killer cells antigen-specific?
NO, they target any cell that shows signs of infection or abnormality, such as virus-infected or cancer cells
What are natural killer (NK) cells?
are a type of lymphocyte that are part of the innate immune system. They do not target specific antigens but are involved in destroying virus-infected and cancerous cells.
What is MHC 1, and why is it important for NK cell targeting?
MHC 1 (major histocompatibility complex) is a protein expressed by all nucleated cells
- role in identifying self-cells, and its reduced expression on virus-infected or cancer cells triggers NK cells to attack these abnormal cells.
What triggers natural killer (NK) cells to attack cells?
are triggered when they detect a combination of stress markers on cells and a lack of protective MHC 1 expression
- Cells infected with viruses or certain cancer cells often reduce MHC 1 expression, making them vulnerable to NK cells
How do natural killer (NK) cells recognize pathogens without being antigen-specific?
express Toll-like receptors, which allow them to recognize pathogen-associated molecular patterns (PAMPs) or damage-associated molecular patterns (DAMPs)
- providing a broader mechanism for activation.
