22.4 The Inflammatory Response

Three short movements: the case, the anatomyThe study of the structure of the human body. and physiologyThe study of how the body functions., then the tie back to Stina. Each links to the scene where you’ll see it move.

I · Fever of unknown origin

In November 2016, with her back finally fixed and the back pain still arriving with every fever, as it always had, she was admitted for a fever of unknown origin. Three days at 39, chills that shook the bed and then sweats that soaked it; a right knee hot, red and swollen that would not bend; a belly that guarded under a hand. The white count was fifteen thousand, almost all neutrophils; the CRP was 148; the sedimentation rate 72. The knee was tapped: twenty-four thousand cells, ninety percent neutrophils, no crystals, no organisms. Three blood cultures and a urine culture grew nothing. On day four it was gone. Gastroenterology cleared her, oncology cleared her, infectious disease cleared her, and the note said what notes say: fever of unknown origin. The origin was known. It had a name, and the name is the chemistry of this chapter.

See it move: Scene 1 · Red, Hot, Swollen, Painful · Scene 4 · Fever: The Thermostat Reset

II · The signs, the chemicals, the cells

Inflammation is the innate arm’s response to injury, and it announces itself in the five cardinal signs the lecture teaches as three signs and a symptom: rubor and calor — redness and heat from arteriolesSmall arteries that regulate blood flow into capillaries through vasoconstriction and vasodilation dilating; tumor — swelling from capillariesThe smallest blood vessels where gas, nutrient, and waste exchange occurs between blood and tissues. leaking plasmaThe liquid component of blood. into the tissue; dolor — pain from the swelling pressing on nerve endings and from the chemicals themselves; and functio laesa, the loss of function that keeps a swollen knee from bending. Behind the signs are chemicals. Mast cells and basophils degranulate histamine (dilation, leakiness) and heparin; the kinins (bradykinin) and the prostaglandins add leakiness and pain, which is why ibuprofen, which blocks prostaglandin synthesis, dulls both; leukotrienes call neutrophils; complement fragments C3a and C5a call everything. The chemicals run the four stages of phagocyte mobilization: leukocytosis, as the marrow releases neutrophils and the count climbs to fifteen thousand; margination, as they slow and roll along the sticky endotheliumThe innermost layer of blood vessels, composed of simple squamous epithelial cells, which reduces fr of the dilated vessels; diapedesis, as they squeeze between endothelial cells into the tissue; and chemotaxis up the gradientMovement from lower to higher concentration. to the source. Neutrophils arrive within an hour, macrophages after a day. Dead neutrophils and the debris they ate are pus; walled off, pus is an abscess; when the target cannot be cleared the macrophages fuse and ring it in a granuloma. Fever runs on the same chemistry one step up: IL-1β, IL-6 and TNF-α from macrophages and neutrophils are endogenous pyrogens; they drive prostaglandin E2 in the hypothalamusA small but vital brain region controlling hormones, temperature, and autonomic functions., and the thermostat resets. The stadium, the chill, is the body heating toward the new set point — shivering, vasoconstrictionThe narrowing of blood vessels due to contraction of smooth muscle, increasing blood pressure and re, cold skinThe body’s largest organ, providing protection and regulation. on a hot patient; the fastigium is the plateau; defervescence, the sweat, is the set point coming back down. A mild fever helps — it slows bacterial growth, speeds leukocytes, and sequesters iron and zinc — which is why it was kept.

See it move: Scene 2 · The Mast Cell and Its Chemicals · Scene 3 · Mobilizing the Phagocytes · Scene 4 · Fever: The Thermostat Reset

III · Sterile

Everything above is correct about her knee, her belly and her fever. It is the trigger that is missing. The full program — leukocytosis to fifteen thousand, a joint full of neutrophils, a CRP of 148, three days of resetting thermostat — ran with no pathogen, no crystal and no injury, and then stopped on its own. The lecture’s own story is here: Amy’s two-and-a-half-year fever of unknown origin, the workup that found nothing because it was looking for a cause outside the body. The acute-phase proteins tell the time: CRP and ESR rise and fall with each flare, as a flare should; serum amyloid A rises with each flare and never quite comes back down, which is the slow part of this disease and the thread the Digestive and Urinary modules followed to the Congo red stain. Sterile inflammation is inflammation whose trigger is the sensor itself. The cardinal signs do not know the difference. The patient’s kidneys, over decades, do.

See it move: Scene 1 · Red, Hot, Swollen, Painful · Scene 5 · Sterile

5 scenes. Each one has a short animation or a slide, something to explore, a true/false spot-check of your thinking, and a quick check. Every scene gives you an evidence card for your board.

Every scene gave you an evidence card, and the chart adds more. Sort each card into the column it supports: Sterile inflammation on an internal trigger, Neither on its own, or An infection the cultures missed. Some cards can honestly go in more than one place — that’s allowed, and the feedback tells you which cards decide the case.

Time to decide. Look back at your bet, then build your verdict from statements that hold up — no writing needed.