Immunology Chapter 1: Innate Immunity

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Questions and Answers

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?

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?

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?

TLR-4 Signup and view all the answers

In the process of phagocyte activation involving LPS, which component directly interacts with TLR-4?

CD14 Signup and view all the answers

What is the role of CD14 in the activation of phagocytic cells through LPS?

It blocks LPS-induced signals. Signup and view all the answers

Which type of cell is primarily responsible for initiating the immune response to pathogens?

Dendritic cells Signup and view all the answers

What is the main difference between monocytes and macrophages?

Monocytes circulate in blood while macrophages reside in tissues. Signup and view all the answers

Which factor primarily influences the differentiation of monocytes into macrophages?

Cytokines released by Helper T cells Signup and view all the answers

Neutrophils are characterized by which of the following features?

They are the first to arrive at the site of inflammation. Signup and view all the answers

What distinguishes NK cells in the immune response?

They act against viruses and tumors. Signup and view all the answers

Which receptor fragments are recognized by pathogens?

Fc portion of Ig and certain fragments of activated complement. Signup and view all the answers

Which cell type is particularly noted for its diverse functions based on site and state of maturation?

Dendritic cells Signup and view all the answers

Which cells are involved in the acute inflammatory response through cytokine release?

Macrophages and neutrophils Signup and view all the answers

What characterizes the process of leukocytosis?

An increase in circulating neutrophils. Signup and view all the answers

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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Description

Dive into the essentials of innate immunity with this quiz covering the immune system's functions of detection and destruction of invaders. Explore how our bodies recognize pathogens through various molecular signatures and receptors. Test your knowledge on the foundational concepts of immunological response mechanisms.