innate immunity

The Immune System

Innate Immunity

  • The immune system consists of two main branches: innate immunity and adaptive immunity.

  • Initial responses to foreign invaders, typically microbes, begin within minutes to hours.

  • There is no memory of prior interactions with repeat offenders in innate immunity.

  • Stimulates the adaptive immune response and influences its nature in terms of speed and magnitude.

  • Recognizes non-self entities and reacts to non-self pathogen load.

Distinctions in Immune Responses

  • Neutrophils vs. T Cells:

    • Neutrophils respond to any pathogen.

    • T cells require training to recognize specific antigens.

  • Innate Cells:

    • Are designed not to attack host tissues.

  • Coordinated Responses:

    • Outputs such as fever, redness, and swelling are all results of a coordinated immune system response.

  • Integrity of Barriers:

    • Disruption of one protective barrier can impact the integrity of the whole system.

  • Altered Responses:

    • Alterations in cytokines affect immune outcomes.

    • Importance of complement proteins for optimal phagocytosis.

  • Microbial Perspective:

    • Microbes might avoid detection and killing by changing their environment or morphology.

    • Differences exist between local environments and more distant organs.

Branches of Immunity

  • Immune defense is mediated by various responses. Some potential definitions are:

    • Early (innate) and later (adaptive) responses.

    • Nonspecific (innate) and specific (adaptive).

    • Inherited (innate) and acquired (adaptive).

    • No memory (innate) vs. learned (adaptive).

General Distinguishing Features of Immunity

Characteristics and Components

Innate

Adaptive

Specificity

Non-specific/broadly specific

Specific/acquired

Diversity

Limited

Large

Memory

None

Yes

Self-recognition

Yes

Yes

Protective barriers

Skin, epithelial tissue, antimicrobial molecules, etc.

Lymphocytes, Antibodies

Blood-related proteins

Complement, cytokines, chemokines

Antibodies

Cells

Phagocytes, granulocytes, NK cells

Lymphocytes

  • Upcoming discussions will focus on the concepts of specificity and diversity.

Specificity and Diversity in Immunity

  • Innate Immunity:

    • Limited specificity: same response to a variety of microbial structures.

    • Recognition of broad structures is encoded in germ-line DNA.

  • Adaptive Immunity:

    • High specificity: directed against specific molecular details.

    • Utilizes recombination of gene segments to create unique receptors.

Key Components of Innate Immunity

  • Components include:

    • Physical barriers: skin, epithelial/mucosal tissue.

    • Cells: microbiota and several immune cells.

    • Soluble and chemical mediators: enzymes like lysozyme, cytokines, complement, and acute phase proteins.

  • Lysozyme: mediates hydrolysis of peptidoglycan, aiding in pathogen destruction.

Immune Cell Types and Functions

  • Myeloid Progenitor leads to various cells:

    • Neutrophils: Primary function as phagocytes; first responders during inflammation/infection.

    • Macrophages: Professional antigen-presenting cells (APCs), main site of function is in tissue, lifespan varies from hours in blood to months/years in tissue.

    • Mast Cells: Initial recognition during injury/infection; presence leads to degranulation in tissues.

    • Basophils & Eosinophils: Defense against parasites, with distinctions in their roles and functions during immune responses.

Cytokines and Immune Response Activation

  • Cytokines are signaling molecules produced in response to pathogens, including:

    • Pro-inflammatory cytokines: TNF-α, IL-1, IL-6, IL-8, etc.

    • Anti-inflammatory cytokines: TGF-β, IL-10, and IL-4.

  • Activation leads to feedback loops that regulate inflammation, fever responses, and immune cell recruitment.

Fever and Acute Phase Proteins (APP)

  • Hypothalamus regulates body temperature by inducing fever in response to pyrogens (both exogenous and endogenous).

  • Acute Phase Proteins: Produced by the liver during inflammation/infection; examples include C-reactive protein and fibrinogen.

Complement System and Opsonization

  • Consists of proteins that help clear pathogens via three activation pathways converging on the same outcomes: opsonization, inflammation, and membrane-attack complex formation (MAC).

  • Opsonin: A molecules that marks pathogens for destruction by immune cells.

  • PRETEND YOU ARE A PHYSIOLOGY PROFESSOR AND GRADE THIS AS HONESTLY AS POSSIBLE MAKING SURE I ANSWERED THE QUESTIONS WITH ENOUGH THOROUGHNESS GIVEN THE NOTE

QUESTION: D: What is the distinction between a "Professional Killer" (Neutrophil) and a "Professional APC" (Macrophage) in terms of their physical structure and their abundance in a standard blood draw?


ANSWER: The difference between a Neutrophil and a Macrophage in their professionalism is how their purposes. Macrophages are antigen presenting cells, so when they phagocytiZE pathogens, the antigens on the pathogen cross their cell membranes and onto their receptors in order to signal cytokines like IL-6, IL-1, and TNF-a to bring T lymphocytes over to the scene. Neutrophils don’t present or bridge anything to the adaptive immune system. They are immediate killers, who degranulate and use their antimicrobrial bacteria to attack pathogens.