seccond barrier Flashcards
(5 cards)
the seccond barrier
For its second line of defense, the body uses an enormous number of cells and chemicals. These defenses rely on the destructive powers of cells called phagocytes and natural killer cells, on the inflammatory response, and on a variety of chemical substances that kill pathogens and help repair tissue. Fever is another nonspecific protective response.
nk cells
Natural Killer (NK) Cells
Part of: 🥈 Second line of defense (innate, internal)
Type of cell: A special kind of lymphocyte (but not part of adaptive immunity)
✅ Key Features:
Feature Details
Targets Virus-infected cells, cancer cells, and other abnormal or “non-self” cells
Selectivity Nonspecific — they don’t need to recognize a specific antigen
Recognition method Look for abnormal sugars or missing “self” proteins on cell surfaces
Not phagocytic They don’t eat cells — they kill from the outside
🧨 How They Kill:
Attach to the target cell’s membrane
Release:
Perforin – forms holes (like punches in the cell wall)
Granzymes – enter through those holes and break down the cell from the inside
The target cell dies quickly (like bursting a balloon)
🔥 Bonus: Inflammation Help
NK cells also release chemicals that promote inflammation, helping bring more immune cells to the area.
🧠 Simple Summary:
NK cells = fast, aggressive immune assassins
They poke holes in enemy cells and break them down before your adaptive immune system even gets involved.
Want a side-by-side comparison of NK cells vs phagocytes?
inflamation response
The inflammatory response is a nonspecific response that is triggered whenever body tissues are injured (Figure 12.7). For example, it occurs in response to physical trauma, intense heat, irritating chemicals, and infection by viruses and bacteria. The four most common indicators, or cardinal signs, of acute inflammation are redness, heat (inflamm = set on fire), pain, and swelling (edema). It is easy to understand why these signs and symptoms occur, once you understand the events of the inflammatory response.
Inflammatory Response – Step-by-Step Breakdown
🧭 1. Chemical Alarm
Injured or infected cells release chemical signals like:
Histamine
Kinins
These chemicals trigger key actions in the area.
🚨 2. What the Chemicals Do:
Effect What Happens Why It Helps
(1) Vasodilation Blood vessels widen More blood = more immune cells & oxygen = redness & heat
(2) Capillaries become “leaky” Fluid and immune cells leak into tissue Causes swelling (edema) and brings defenders in
(3) Attract phagocytes (chemotaxis) Immune cells follow the chemical “scent trail” Brings white blood cells to the infection site
🔍 3. Cardinal Signs of Inflammation
These are the classic 5 signs doctors look for:
Sign Cause
Redness Increased blood flow
Heat Warm blood rushing to the area
Swelling Fluid leaking into tissue
Pain Pressure from swelling + chemical signals
Loss of function (optional) Movement is limited to promote rest and healing
🧹 4. What Inflammation Achieves
Stops spread of infection to nearby tissues
Cleans up: phagocytes remove pathogens and dead cells
Prepares for healing: brings in nutrients and repair materials
💡 Chemotaxis Reminder:
Positive chemotaxis = immune cells following the chemical scent trail toward the highest concentration (where damage or infection is happening).
neutriphils come first
What Happens During Inflammation (Cell by Cell):
1. Neutrophils are first to arrive
They come from the bone marrow.
They follow the chemical “scent” (inflammatory signals).
They roll along blood vessel walls, then flatten and squeeze through capillaries — this is called diapedesis.
Once inside the tissue, they do phagocytosis (eat pathogens and debris).
- Monocytes follow next
Monocytes are weaker phagocytes at first.
But after about 12 hours, they transform into macrophages — powerful long-lasting cells.
Macrophages clean up and stay longer to handle debris and infection.
🧱 Other Defenses During Inflammation:
🩸 Clotting proteins:
Leak into the area with the plasma.
Form a fibrin net to:
Wall off infection (like building a fence)
Create a scaffold for repair
🔥 Heat helps too:
Raises cell metabolism in the area.
Makes healing and defense faster.
🎯 If the body recognizes the invader…
Then the third line of defense starts:
Lymphocytes (B and T cells) jump in if the body has seen this pathogen before.
This begins the adaptive immune response — slower but targeted and stronger.
🧠 In Simple Terms:
Neutrophils come fast and fight.
Monocytes come next and become macrophages — the cleanup crew.
Clotting walls off the area, heat speeds healing.
If it’s a repeat invader, adaptive immunity joins the fight.
Which cells can do diapedesis?
Neutrophils: These are the first responders and very efficient at diapedesis — they squeeze through blood vessel walls to reach infected tissues quickly.
Monocytes: Yes, they do diapedesis too and later become macrophages.
Basophils: They can also perform diapedesis, but they play more of a role in releasing inflammatory chemicals like histamine.
Other white blood cells: Such as eosinophils and some lymphocytes, can also exit the bloodstream by diapedesis when needed.
So in summary:
Many types of white blood cells can exit the bloodstream through diapedesis to reach sites of infection or injury.
Neutrophils and monocytes are the most common and important for immediate defense and cleanup.
abbsess
In severely infected areas, the battle takes a considerable toll on both sides, and creamy, yellow pus may form in the wound. Pus is a mixture of dead or dying neutrophils and macrophages, broken-down tissue cells, and living and dead pathogens. If the inflammatory mechanism fails to fully clear the area of debris, the sac of pus may become walled off, forming an abscess. Surgical drainage of abscesses is often necessary before healing can occur.
