BIO 2010 Microbiology - Chapter 6A: Non-Adaptive Immunity Notes

Two Arms of the Immune System

• Non-Adaptive Immunity

  • Includes intrinsic and innate defenses.

  • Same response for all pathogen types.

• Adaptive Immunity

  • Specific responses for each microorganism.

Non-Adaptive Immunity: Lines of Defense

• First Line: External body membranes (skin and mucosae).

• Second Line: Antimicrobial proteins, phagocytes, and other cells; inflammation is key.

• Characteristics:

  • General response system functioning the same way, eliminating almost all pathogens.

  • Does not identify individual pathogens.

Adaptive Immunity: Third Line of Defense

• Attacks particular foreign substances, slower to react.

• Adaptive system tailors its response to individual pathogens.

• Innate and adaptive defenses are intertwined.

Surface Barriers

• Skin, mucous membranes, and secretions act as physical barriers.

• Keratin resists acids, bases, bacterial enzymes, and toxins.

• Mucosae provide similar mechanical barriers.

Protective Chemicals

• Inhibit or destroy microorganisms.

  • Skin acidity.

  • Lysozyme in saliva and lacrimal fluid.

  • Mucus.

Intrinsic Processes

• Always present in uninfected cells; includes:

  • Apoptosis.

  • Autophagy.

  • RNA silencing.

  • Antiviral proteins.

Apoptosis

• Programmed cell death; intrinsic (self-initiated) and extrinsic (induced by external signals).

  • Neutrophils undergo apoptosis after about 1 day.

CISPR

• Mechanism bacteria use to edit their DNA after virus insertion.

Pattern Recognition

• Pathogen attaches to multiple host receptors, triggering a specific immune response.

• Non-adaptive immunity uses cell receptors that recognize pathogen-associated molecular patterns (PAMPS).

Cytokines

• Secreted proteins that kill bacteria or infected host cells after patterned attachment signals.

Innate Immunity

• Attacks pathogens without specificity, acts quickly.

• Cells and proteins needed if microorganisms invade deeper tissues.

• Antimicrobial proteins (interferons and complement proteins).

• Inflammation/Fever.

Macrophages

• Ingest and eliminate infectious agents; present antigens.

• Attracted by chemicals from dying cells.

Dendritic Cells

• Specialized for antigen presentation and T-cell activation (adaptive immunity).

• Migrate to lymphoid organs with antigen.

Lymphocytes

• T-lymphocytes: seek and destroy.

• B-lymphocytes: produce antibodies.

MHC Protein

• Specific MHC protein matches the original antigen absorbed by the cell and moves to the cell surface.

• MHC attachment programs the cytotoxic T-Lymphocyte (CTL).

Natural Killer (NK) Cells

• Recognize normal vs. low "self" protein (MHC) levels.

• Release perforins (punch holes) and granzymes (induce apoptosis).

T-Cell Receptors (TCRs) and CD28 Receptors

• TCR function is recognition, and CD28 is activation.

Neutrophils

• Become phagocytic upon encountering infectious material.

• Release toxic chemicals and induce intrinsic apoptosis.

Mast Cells

• Release substances (e.g., histamine) contributing to inflammation.

• Important in allergic responses and innate immunity.

• Antihistamines: competitive inhibitors of histamine receptors.

Antimicrobial Proteins (Cytokines)

• Interferons (IFNs) and complement proteins.

  • Attack microorganisms or hinder reproduction.

Interferons (IFNs)

• Signal response to viral and some cancer infections.

• Induce antiviral proteins in host cells.

• Guide NK cells to release perforin and stimulate macrophage consumption.

• Cause flu-like symptoms.

Complement Proteins

• Proteins circulating in the blood in an inactive state.

• Play a role in inflammatory responses.

• Create osmotic imbalance.

• Antibodies activate complement.

Inflammation

• Response of vascular tissue to injury or infection.

  • Seeks to destroy injurious agents and confine them.

• Sequence of events:

  • Histamine release, capillary widening, increased permeability, leukocyte attraction, fever.

Fever

• Triggered by bacterial endotoxins.

• Positive Effects: Stimulates phagocytosis, slows bacterial growth.

• Negative Effects: Extreme heat, enzyme denaturation (above 39°C is dangerous).

• Moderated by the medulla oblongata.