White Blood Cell Types and Functions

White Blood Cell Types and Functions

• Neutrophils: Most abundant, first responders to infection, crucial in phagocytosis.
• Lymphocytes: Include B cells (produce antibodies), T cells (cell-mediated immunity), and natural killer (NK) cells (destroy infected/cancerous cells).
• Monocytes: Largest WBC type, differentiate into macrophages and dendritic cells. Macrophages are crucial for phagocytosis and antigen presentation. Dendritic cells are antigen-presenting cells that activate T cells, key in adaptive immunity.
• Eosinophils: Attack parasites and play a role in allergic reactions.
• Basophils: Release histamine and other mediators important in inflammation and allergies.

Phagocytosis Steps

• Recognition and Attachment: Phagocytic cells recognize pathogens via surface receptors (like Toll-like receptors).
• Engulfment: The pathogen is enclosed within a membrane-bound vesicle (phagosome).
• Phagolysosome Formation: The phagosome fuses with a lysosome (containing enzymes).
• Destruction: Lysosomal enzymes kill and digest the pathogen.

Chemotaxis Definition and Purpose

• Chemotaxis: Movement of cells in response to chemical signals.
• Purpose: Crucial for immune cells to locate and target infection sites. Certain molecules (chemoattractants) released from damaged tissues or pathogens attract immune cells to guide them to the area.

Complement Activation and Significance

• Activation: The complement system is a group of proteins that work together to enhance the immune response. Activation can be initiated by various factors.
• Significance: Enhances phagocytosis (opsonization) of pathogens, recruits other immune cells (chemotaxis), and directly kill some pathogens and infected cells through lysis.

Lines of Defense Differences

• First Line: External barriers (skin, mucous membranes), physical mechanisms. Primarily prevent entry of pathogens.
• Second Line: Includes phagocytes (neutrophils, macrophages), inflammation, complement, fever. Innate and non-specific.
• Third Line: Adaptive or acquired immune response involving specific lymphocytes (B and T cells), antibodies, immunological memory.

Inflammation: Initiation and Molecules

• Initiation: Tissue damage triggers a cascade of reactions involving various molecules.
• Molecules: Histamine, cytokines, chemokines, complement components; promote vasodilation and increased vascular permeability, attracting phagocytes, thus initiating the inflammatory response.

Inflammatory Symptoms

• Local Symptoms: Redness, heat, swelling, pain result from increased blood flow, fluid leakage, and the activity of immune cells.
• Systemic Symptoms: Fever, fatigue, etc often accompany more extensive inflammation.

Pathogen-Associated Molecular Patterns (PAMPs)

• Definition: Molecules found on pathogens that are recognized by immune cells.
• Importance: Trigger innate immune responses.
• Examples: Lipopolysaccharides (LPS) from gram-negative bacteria; peptidoglycans from bacterial cell walls; flagellin from bacterial flagella; viral nucleic acids.

Monocytes: Lineage and Functions

• Definition: A type of white blood cell.
• Differentiation: Monocytes differentiate into macrophages and dendritic cells.
• Macrophages: Phagocytic cells, crucial for eliminating pathogens, cellular debris and antigen presentation.
• Dendritic cells: Activate T cells to initiate adaptive immune responses.

Opsonization: Mechanism and Rationale

• Definition: Coating of pathogens with molecules that enhance phagocytosis.
• Mechanism: Antibodies or complement proteins can coat pathogens, making them more attractive targets for phagocytic cells.
• Rationale: Improves phagocytic efficiency by facilitating the recognition and engulfment of the target pathogen.

Cytokine Role in Fever

• Role: Certain cytokines (e.g., interleukins) can stimulate the hypothalamus to raise the body temperature. This results in a fever response, slowing down or inhibiting microbial growth.

Leukocytes: Types and Functions

• Definition: A type of white blood cell, involved in the immune response.
• Types and Functions (covered previously under other sections in more detail): Neutrophils, lymphocytes (B cells, T cells, natural killer cells), monocytes, eosinophils, basophils, macrophages, dendritic cells. Note specialization in function from the different types.

This quiz explores the various types of white blood cells and their essential functions in the immune system. Understand the roles of neutrophils, lymphocytes, monocytes, eosinophils, and basophils in fighting infections and maintaining health. Test your knowledge on the steps involved in phagocytosis and immune responses.