Bacterial Infection Flashcards
What is the first stage of a bacterial infection?
There is a break in the epithelial surface which allows the bacteria to enter and proliferate
Which two pathways can be activated to initiate bacteria cell lysis?
Alternative complement pathway or the mannan binding lectin pathway
What does complement activation lead to? (3)
Mast cell activation, opsonisation and chemotaxis
What binds to bacteria to activate complement?
C-reactive protein
What does mast cell degranulation cause? (2)
Increased blood flow and leaky blood vessels, causes oedema and local irritation
What cells are recruited first in the complement pathway?
Neutrophils
What is the role of a neutrophil?
Phagocytosis
What is the role of a dendritic cell?
Engulf and internalise bacteria
Where do dendritic cells take bacteria?
Lymph nodes
What cells recruit T-cells in the lymph nodes?
Dendritic cells
How do dendritic cells interact with T-cells in the presence of bacteria?
Dendritic cells present bacteria peptide to the naive T helper cells on their MHC II molecules which activates T cells
Which T helper cells are activated by dendritic cells?
T helper 1 and T helper 2
What is the role of activated T helper 2 cells?
Cause B cells to become plasma cells and produce antibodies
What is the first antibody to be produced?
IgM followed by IgG or IgA
What are the benefits of IgM? (3)
5 binding sites to enhance efficiency, good opsonin and activates the classical complement pathway
What engulfs opsonised bacteria?
Phagocytes
How is bacterial debris removed after an infection is controlled?
Neutrophils or by antibodies as soluble immune complexes
What is the classical pathway?
Antigen-antibody complexes in pathogen surfaces, release C1q, C1r, C1s, C4 and C2
What is the MB-Lectin pathway?
Mannan binding lectin binds mannose on pathogen surfaces, releasing MBL, MASP-, MASP-2, C4 and C2
What is the alternative pathway?
Pathogen surfaces, release of C3, B and D
What is the common pathway?
C3 convertase causes the generation of C3a, C3b and C5a
What do C3a and C5a cause?
Peptide mediators of inflammation to be activated and phagocyte recruitment
What does C3b do?
Binds to complement receptors on phagocytes to cause opsonisation of pathogens and removal of immune complexes
What are the terminal complement components?
C5b, C6, C7, C8 and C9
What do C5b, C6, C7, C8 and C9 cause?
Membrane attack complex, lysis of certain pathogens and cells
