Myeloid Cells and the Innate Immune Response

What are myeloid cells?

A subset of leukocytes that play a crucial role in the innate immune system.

Name the major types of myeloid cells.

Granulocytes (neutrophils, eosinophils, basophils, mast cells) and monocytes/macrophages.

What role do dendritic cells play in the myeloid cell category?

Act as antigen-presenting cells.

What characterizes granulocytes?

The presence of granules in their cytoplasm containing enzymes and other substances important for immune responses.

What is the primary role of neutrophils?

Target bacteria.

What role do eosinophils serve?

Combat parasites.

What is the role of basophils?

Participate in allergic responses.

How does the innate immune system respond to pathogens?

It responds quickly and non-specifically.

What do Pattern Recognition Receptors (PRRs) do?

They recognize pathogens through patterns and triggering immune responses.

What are Toll-like receptors (TLRs)?

A key type of PRR that detects bacteria and viruses.

What do NOD-like receptors (NLRs) detect?

Intracellular bacteria.

What do C-type lectin receptors (CLRs) detect?

Fungi.

What do TLRs recognize?

Pathogen-Associated Molecular Patterns (PAMPs) like LPS and dsRNA.

What is NFκB?

A master transcription factor for inflammatory mediators activated by TLRs.

What major cell types are part of the innate immune system?

Macrophages, neutrophils, eosinophils, basophils, and mast cells.

What are antimicrobial proteins?

Proteins crucial for direct pathogen elimination, including lysozyme and defensins.

What is phagocytosis?

The process by which innate immune cells engulf and destroy extracellular material.

Which cells are considered main phagocytes?

Neutrophils, eosinophils, basophils, monocytes, macrophages, and dendritic cells.

What is the role of reactive oxygen species (ROS) in immune response?

Produced by activated phagocytes to kill pathogens, but can also damage surrounding tissues.

What is Chronic Granulomatous Disease (CGD)?

A condition where patients have a deficiency in NADPH oxidase, increasing susceptibility to infections.

What is lysozyme and where is it found?

An antimicrobial protein that breaks down bacterial cell walls, found in tears and saliva.

What are defensins?

Small peptides that disrupt microbial membranes, secreted by phagocytes and epithelial cells.

What are histatins known for?

Their antifungal activity, particularly against Candida species.

How do granulocytes contribute to the immune response?

They release granules containing antimicrobial agents and enzymes upon activation.

What are NETs in the context of neutrophils?

Neutrophil extracellular traps that capture and kill pathogens using nuclear chromatin and antimicrobial proteins.

What is the complement system?

A system consisting of over 30 proteins that enhance the ability of antibodies and phagocytic cells to clear pathogens.

What are the three pathways of complement activation?

Classical, lectin, and alternative.

What is opsonization?

The process of marking pathogens for destruction by phagocytes.

What is the Membrane Attack Complex (MAC)?

A structure formed by the complement system that directly lyses pathogens.

What triggers the classical pathway of complement activation?

Antibody-antigen complexes.

What initiates the lectin pathway of complement activation?

Mannose-binding lectin (MBL) binding to carbohydrates on pathogens.

How is the alternative pathway of complement activation characterized?

It is activated spontaneously on pathogen surfaces.

What can deficiencies in complement components lead to?

Increased susceptibility to infections, especially with encapsulated bacteria.

How can some pathogens evade the immune response?

By inhibiting complement activation.

What is the relevance of understanding complement pathways?

It is crucial for developing therapies for autoimmune diseases and infections.

What is Flow Cytometry (FACS)?

A technique used to analyze immune cell populations and their activation states.

What specific markers can be used in FACS to identify macrophage activation?

CD18, TLR4, CCR1, and CCR5.

What can the analysis of cell counts and surface markers provide?

Insights into immune responses during infections.

What specific type of immune response do neutrophils primarily target?

Extracellular bacteria.

What role do mast cells play in the innate immune system?

They release mediators involved in allergic responses.

How do pattern recognition receptors (PRRs) ensure broad recognition of pathogens?

They are expressed by all cells of a particular type.

What is the primary function of macrophages?

Engulf and destroy pathogens, and present antigens to activate adaptive immunity.

Describe the respiratory burst in phagocytes.

A rapid increase in oxygen consumption resulting in the production of reactive oxygen species.

What is the significance of the activation of NFκB in immune responses?

It leads to the production of pro-inflammatory cytokines and chemokines.

What role do cytokines and chemokines play in the immune response?

They recruit additional immune cells to the site of infection.

What is the function of defensins in the immune system?

They disrupt the microbial membranes of pathogens.

What substance do phagocytes create to kill pathogens during the respiratory burst?

Hydrogen peroxide (H2O2).

What does the term 'innate immune system' refer to?

The body's first line of defense against pathogens, providing rapid and non-specific responses.

What can occur if there is a dysfunction in the complement system?

Increased risk of infections and potential autoimmune disorders.