Innate Immune System Flashcards

Focuses on the components and types of cells involved in the innate immune system.
Recognizes the role of these cells in identifying pathogens and microbes.

Understand key features of innate immunity.
Learn about Pattern Recognition Receptors (PRRs) and their role in identifying pathogens.
Differentiate between Pathogen-Associated Molecular Patterns (PAMPs) and Damage-Associated Molecular Patterns (DAMPs).
Identify immune cells that belong to the innate immune system.
Discuss limitations of the innate immune response and the significance of dendritic cells.

Basic immune systems exist in all forms of life, with innate systems in plants and simpler organisms.
Jawed vertebrates evolved immunological capabilities around 360 million years ago.
Lymphocyte-like cells emerged roughly 5 million years ago.

Neutrophils: The most abundant type of white blood cell, key players in the immune response.
Basophils: Involved in inflammatory reactions.
Eosinophils: Important in combating multicellular parasites.
Monocytes/Macrophages: Differentiate into macrophages in tissues, crucial for phagocytosis.
All these cells arise from a common myeloid progenitor.

Speed: Rapid response, akin to Usain Bolt.
Short-lived: Cells live hours to days and respond in a repetitive manner without adaptation.
Interactivity: Communicates with other immune and epithelial cells without reacting to the host.
Response Timing: Typically initiates response within minutes to days, transitioning to adaptive immunity after 1-2 days.

The innate immune system detects patterns using PRRs, which do not rely on B or T cell receptors.
PAMPs: Recognized on foreign pathogens (e.g., bacterial LPS).
DAMPs: Recognized on damaged self-cells (e.g., DNA, ATP from dead cells).

PRRs are crucial for recognizing PAMPs and DAMPs, initiating immune responses.
Different types of PRRs include:
- Toll-Like Receptors (TLRs): Found on cell surfaces and endosomes, involved in detecting a variety of microbial patterns.
- NOD-like Receptors (NLRs): Present in the cytoplasm, detect intracellular pathogens.
- RIG-like Receptors (RLRs): Recognize viral RNA in the cytosol.
- C-Type Lectin Receptors (CLRs): Recognize carbohydrates.

Examples of TLRs and their targets:
- TLR1 and TLR2: Recognize triacyl lipopeptides.
- TLR2 and TLR6: Recognize diacyl lipopeptides.
- TLR3: Recognizes double-stranded RNA.
- TLR4: Recognizes LPS from gram-negative bacteria.
TLRs activate transcription factors, signaling to the nucleus and initiating immune responses.

Phagocytes recognize pathogens through multiple receptors, enhancing the uptake process.
The formation of a phagosome and its fusion with lysosomes to create phagolysosomes is critical for pathogen destruction.
Key cytokines produced during this process include TNF-alpha and interleukins (IL-1, IL-6, IL-12).

Dendritic cells are essential antigen-presenting cells, bridging the innate and adaptive immune systems.
They capture and process antigens from pathogens, then migrate to lymph nodes.
Mature dendritic cells express more MHC molecules to present antigens to T cells, activating adaptive immunity.

Characteristics: Rapid, short-lived, repetitive, nonreactive to the host.
Classification of innate immune cells into phagocytes (e.g., neutrophils, macrophages) and antigen-presenting cells (e.g., dendritic cells).
It's essential to recognize PAMPs and DAMPs as triggers for immune responses, with PRRs initiating cascades that recruit additional immune cells.

Innate immunity is integral but often insufficient alone, necessitating collaboration with adaptive immunity for effective pathogen clearance.