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Questions and Answers
What is the primary function of Pattern Recognition Receptors (PRRs) in the immune response?
What is the primary function of Pattern Recognition Receptors (PRRs) in the immune response?
- To produce antibodies specific to pathogens
- To identify and respond to immunogenic peptides
- To perceive molecular signatures of pathogens (PAMPs) (correct)
- To mediate direct killing of invading cells
What is the role of LPS in the context of TLR-4 activation?
What is the role of LPS in the context of TLR-4 activation?
- It enhances the production of complement proteins
- It serves as a toxin that directly kills immune cells
- It acts as an antigen for B cell activation
- It binds to LBP to initiate phagocytic cell activation (correct)
Which of the following correctly describes a characteristic of PAMPs?
Which of the following correctly describes a characteristic of PAMPs?
- They are relatively invariant and shared by large groups of pathogens (correct)
- They are exclusive to specific pathogens
- They are primarily produced by host cells during infection
- They are only found in Gram-positive bacteria
Which receptor is specifically associated with recognizing LPS from Gram-negative bacteria?
Which receptor is specifically associated with recognizing LPS from Gram-negative bacteria?
In the process of phagocyte activation involving LPS, which component directly interacts with TLR-4?
In the process of phagocyte activation involving LPS, which component directly interacts with TLR-4?
What is the role of CD14 in the activation of phagocytic cells through LPS?
What is the role of CD14 in the activation of phagocytic cells through LPS?
Which type of cell is primarily responsible for initiating the immune response to pathogens?
Which type of cell is primarily responsible for initiating the immune response to pathogens?
What is the main difference between monocytes and macrophages?
What is the main difference between monocytes and macrophages?
Which factor primarily influences the differentiation of monocytes into macrophages?
Which factor primarily influences the differentiation of monocytes into macrophages?
Neutrophils are characterized by which of the following features?
Neutrophils are characterized by which of the following features?
What distinguishes NK cells in the immune response?
What distinguishes NK cells in the immune response?
Which receptor fragments are recognized by pathogens?
Which receptor fragments are recognized by pathogens?
Which cell type is particularly noted for its diverse functions based on site and state of maturation?
Which cell type is particularly noted for its diverse functions based on site and state of maturation?
Which cells are involved in the acute inflammatory response through cytokine release?
Which cells are involved in the acute inflammatory response through cytokine release?
What characterizes the process of leukocytosis?
What characterizes the process of leukocytosis?
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Study Notes
Innate Immunity Overview
- Immune system functions include detection and destruction of invading organisms.
- Detection relies on interactions between invaders and host molecules that differentiate self from non-self.
Pathogen Perception
- Pathogen Associated Molecular Patterns (PAMPs) allow the immune system to perceive molecular "signatures" on microbes.
- Common PAMP examples:
- Peptidoglycan from Gram-positive bacteria
- Lipopolysaccharide (LPS) from Gram-negative bacteria
- PAMPs are not found in host cells, are consistent across various pathogens, and are stable structures.
Pattern Recognition Receptors (PRRs)
- PRRs recognize PAMPs to initiate immune responses.
- Toll-Like Receptors (TLRs) are a key example of PRRs:
- TLR-2 recognizes proteoglycans from Gram-positive bacteria.
- TLR-4 binds LPS from Gram-negative bacteria.
LPS and Its Effects
- LPS acts as an endotoxin and can cause septic shock during infections by Gram-negative bacteria.
- TLR-4, in conjunction with CD14, plays a crucial role in phagocyte activation by LPS.
- Binding of LPS to LBP forms a complex that interacts with CD14, leading to phagocyte activation via the transcription factor NFκB.
Humoral Factors in Immune Response
- Humoral factors include immunoglobulins (Ig) and activated complement fragments.
- Pathogens may possess receptors for the Fc portion of Igs and specific fragments of the complement (e.g., CR1, CR3).
Immune Cell Actors
- Key immune cells involved in innate immunity:
- Phagocytes: Monocytes, macrophages, neutrophils, dendritic cells.
- Natural Killer (NK) cells.
Hematopoiesis
- Origin of immune cells from pluripotent stem cells, which can differentiate into:
- Myeloid stem cells and lymphoid stem cells.
- Myeloid stem cells give rise to neutrophils and mononuclear cells (monocytes, macrophages, dendritic cells).
Monocytes and Macrophages
- Monocytes circulate in blood; macrophages function within tissues.
- Maturation from monocytes to macrophages increases size and complexity, enhancing phagocytic capacity.
- Activation of macrophages occurs through:
- Pathogen contact and phagocytosis.
- Cytokine stimulation from Helper T cells.
Neutrophils
- First responders during inflammation, recruited via chemotaxis.
- Contain granules that fuse with phagosomes for pathogen digestion.
- Leukocytosis refers to a temporary increase in circulating neutrophils.
Dendritic Cells
- Langerhans cells are a type of dendritic cell that patrol tissues.
- Their function varies based on tissue location and maturation state.
Natural Killer (NK) Cells
- Large lymphocytes crucial for defense against viruses and tumors.
- Produce cytokines that regulate both innate and adaptive immunity, notably IFNγ, which stimulates macrophages and Helper T cells.
- Activated by cytokines such as IFN-α, IFN-β, and IL-12.
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