Mechanisms of Host Defense (Buxton) Flashcards
What type of cells make up innate defenses against extracellular microbes? What do they do?
Phagocyte - a cell (e.g. WBC) that engulfs and consumes foreign material (e.g. microorganisms) and debris
Complement - group of proteins in normal blood serum and plasma that in combination with antibodies causes the destruction especially of particulate antigens (as bacteria and foreign blood corpuscles)
What are the host defenses against extracellular microbes?
Innate defenses, antibody, CD4 cells
What cytokines do CD4 cells secrete against extracellular microbes? What do they do?
Th17 - helps induce neutrophil response (IL-17 causes more neutrophils to be produced in the bone marrow
Th2 - helps produce IgE (if dealing with parasite), also some other Ig
What are the host defenses against intracellular microbes?
Innate defenses, CD4 cells, CD8 cells
What types of cells make up innate defenses against intracellular microbes? What do they do?
NK cells - large granular lymphocyte capable especially of destroying tumor cells or virally infected cells without prior exposure to the target cell and without having it presented with or marked by a histocompatibility antigen
Macrophages - phagocytic tissue cell of the immune system that may be fixed or freely motile, is derived from a monocyte, functions in the destruction of foreign antigens (as bacteria and viruses), and serves as an antigen-presenting cell
What cytokines do CD4 cells secrete against intracellular microbes? What do they do?
Th1 - secretes IFN-γ and TNF-α, activates macrophages to kill microbes located within the macrophages’ phagosomes. Also activate cytotoxic T cells to kill infected cells.
How does the body rid itself of viruses via the immune system?
Innate - IFN-alpha (protects cells in immediate environment that haven’t been infected yet), NK cells
Adaptive - CTLs
What is the most important cell in recovery from viral infections?
CTLs (CD8 cells)
What type of cell provides protection from re-infection or infection following vaccination?
Neutralizing antibody
What does type I IFN do to Class I MHC molecules?
Upregulates expression of them so that CD8 cells recognize antigens from them
Describe the cytotoxicity of CD8 T cells.
Antigen recognition and conjugate formation - CTL activation - granule exocytosis (granules contain perforin that acts like MAC and allows for granzymes to enter cell) - detachment of CTL - target cell death
What does it mean to neutralize the virus?
Blocking virus-receptor reaction
What do vaccines do?
Stimulate production of memory B cells and plasma cells that will secrete appropriate IgG if exposed to that virus
A 5 y/o child develops bacterial otitis media due to Streptococcus pneumonia. If opsonins and neutrophils are mounted in defense by the child’s immune system, what are the opsonins?
IgG & C3b
A 57 y/o man develops bacterial pneumonia due to Legionella pneumophila. What is the most important defense mounted by the man’s immune system?
Th1 cells and gamma interferon
