PMI02-2002 Introduction to host defence Flashcards
What is the immune system?
A communication network of cells and chemical signals distributed in blood and tissues which regulates normal growth and development of the organism while protecting against disease
Where do B cells stem from?
Bone marrow
Where do T cells stem from?
Thymus
What occurs at secondary lymphoid sites?
Lymphocytes interact with each other to generate an immune response
What is the difference between innate and adaptive immunity?
Innate is non-specific, has no memory and is immediate
Adaptive is specific, has memory and its effects are delayed
What organisms is adaptive immunity restricted to?
vertebrates
What are antibacterial peptides secreted by?
epithelial cells
How do antibacterial peptides kill cells?
Damage the microbial cell wall
Why do epithelia secrete mucus?
Microbes find it harder to adhere to surfaces
Flow of mucus washes microbes away
What are the three pathways of the complement system?
Classical pathway
MB-Lectin pathway
Alternative pathway
What is opsonisation?
The process by which a pathogen is marked for ingestion and destruction by a phagocyte
What does complement activation lead to?
Recruitment of inflammatory cells
Opsonisation of pathogens
Killing of pathogens
Which phagocytic cells circulate in the blood only?
Monocytes and neutrophils
What phagocytic cells circulate in tissues only?
Macrophages
What phagocytic cells circulate in blood and tissues?
dendritic cells
Summarise phagocytosis
Phagocytes are recruited to the site of the infection by chemokines
Phagocytes bind to the pathogens
Phagocytosis occurs
Phagosome fuses with a lysosome to form a phagolysosome
Pathogen dies from reactive oxygen and nitrogen produced by the lysosome
What cells bridge the gap between innate and adaptive immunity?
Dendritic cells
What is the purpose of dendritic cells in bridging innate and adaptive immunity?
They capture microbes and take it to lymph nodes to induce adaptive immunity
What initially occurs when dendritic cells engulf the microbes?
Processing
The microbes are digested into small peptide fragments
Presentation
What molecules are antigens presented on?
MHC Class I molecules
MHC Class II molecules
What pathogens are presented on MHC class I molecules?
Internal pathogens or viruses
What pathogens are presented on MHC class II molecules?
external pathogens or bacteria
Where does the MHC/ antigen complex go after it is formed?
Taken to the surface of the dendritic cell and presented to T cells
Which cells do MHC class I induce?
CD8+ T cells (cytotoxic T cells)
Which cells do MHC class II induce?
CD4+ T cells (T helper cells)
How do dendritic cells enter the lymph node?
Via the afferent lymphatic vessel
Where do dendritic cells activate T cells?
In the paracortical area of lymph node
Where do dendritic cells activate B cells?
In the germinal centre of the lymph node
Where do T and B cells gather and leave the lymph node?
Through the efferent lymphatic vessel
How does Th0 produce 4 different Th cells?
Through the secretion of different cytokines
What occurs when things in the immune system go wrong?
Microbes are too advanced for the immune system (Virus can hide inside cells eg: HIV)
Cancers growing unchecked (normal signals for cell growth or death fail)
Harmless substances are deemed dangerous (allergies)
Autoimmune system attacks itself (diabetes, rheumatoid arthritis)
