Organized objective-by-objective. For each one, the goal is: “Can I speak to this?” Use the checkpoint boxes to self-test. 🔗 flags mark concepts that bridge into other modules (this lecture leans heavily on the Lymphatic and Hematology modules).
The immune system is a two-layer defense that funnels into the lymphatic system. The innate response is fast, non-specific, and does the same thing to every pathogen (inflammation). The adaptive response is slow, specific, and remembers. The critical link between them is the antigen-presenting cell (APC), which carries a piece of the pathogen through the lymphatics to the secondary lymphoid structures (nodes, spleen) where B and T cells live. That single hand-off is the spine of the whole lecture — almost every objective connects back to it. The back third of the deck covers the infectious process (how pathogens spread and cause disease) and PT-relevant factors (exercise, immunosuppression).
The four functions of the immune system: (1) protect the body from foreign pathogens; (2) activate “clean-up” of damaged/dead cells after infection or trauma; (3) stimulate an inflammatory cascade (rids the body of the cause of injury + activates the vascular/cellular response); (4) differentiate foreign pathogens from self.
External (barriers): - Physical/mechanical: skin, mucus, cilia lining mucosa; mechanisms like coughing, sneezing, peristalsis. - Biochemical: lysozymes in tears, saliva, stomach HCl, vaginal secretions. - Healthy bacterial flora.
Internal: - Innate — soluble factors (complement, cytokines, chemokines) + cellular components (phagocytes). - Adaptive — lymphocytes (B-cells and T-cells).
Sort every immune cell into its branch, and know each cell’s identifying feature:
| Branch | Cell | Identifying characteristic |
|---|---|---|
| Innate | Neutrophil | Most plentiful WBC (up to 80%); phagocytic; multilobed nucleus; first responder |
| Innate | Macrophage | Large phagocyte; engulfs debris; matures from monocytes; can act as an APC |
| Innate | Dendritic cell (APC) | Star-shaped, sits between tissue cells; displays antigen — the innate→adaptive bridge |
| Innate | NK cell | Large lymphocyte; ~5% of lymphocytes; kills via perforins |
| Adaptive | B-cell | 25% of lymphocytes; humoral; differentiates into plasma + memory cells |
| Adaptive | T-cell | 70% of lymphocytes; cell-mediated; CD4+ helper or CD8+ cytotoxic |
(NK cells arise from the lymphoid line but function as innate.) The deeper functional detail on neutrophils, macrophages, and NK cells lives under Objective 5 below — here the goal is just recognizing what each cell is.
☐ Can I speak to it? Can I name each immune cell, sort it into innate vs. adaptive, and give its identifying feature (e.g., neutrophil = 80% of WBCs, B = 25% of lymphocytes, T = 70%)?
The memory hook: primary = production (diversity), secondary = selection.
☐ Can I speak to it? Can I name which structures make B/T cells vs. select them, and explain why the secondary structures sit where lymph and blood are filtered?
🔗 Cross-module: the lymphoid organs (spleen, bone marrow, nodes, Peyer patches) are the exact structures from the Lymphatic and Hematology modules. Hematopoiesis (the stem-cell → mature-cell tree) is explicitly “not on the exam” here, but recognize that myeloid stem cells feed mostly innate cells and lymphoid stem cells feed the adaptive B/T cells (+ NK).
Innate = first line of defense (0–6 hours), non-specific, no memory. Its primary job is to initiate the acute inflammatory response. It has a cellular arm and a chemical arm.
Rubor (redness) · Calor (heat) · Tumor (swelling) · Dolor (pain).
☐ Can I speak to it? Can I explain why neutrophils are “first,” what margination is, how NK cells kill, and how prostaglandins produce the four cardinal signs?
🔗 Cross-module: “↑ vascular permeability → fluid into interstitial space → swelling” is the edema mechanism from Fluid Dynamics, now driven by immune signaling. Neutrophil/WBC counts tie to the Hematology WBC differential.
| Innate | Adaptive | |
|---|---|---|
| Speed | First line, 0–6 hours | > 12 hours after innate begins |
| Specificity | Non-specific (detects features common to all pathogens) | Targeted to a specific pathogen |
| Key players | Phagocytes + complement; neutrophils = first WBC | Lymphocytes: B-cell (humoral) + T-cell (cell-mediated) |
| Memory | None | Yes (basis of immunizations) |
| Selection | — | B/T cells selected by affinity for antigen (~10⁸) |
The one-line contrast: innate is fast, generic, forgetful; adaptive is slow, specific, and remembers. They aren’t separate systems — innate initiates adaptive through the APC bridge (Objective 4).
☐ Can I speak to it? Can I give the four axes of difference (speed, specificity, memory, key cells) without notes, and explain how the two connect?
This is the single most important connection in the lecture.
Dendritic cells (a type of APC) sit between tissue cells and: 1. Phagocytose the pathogen and display its genetic material on their own membrane. 2. Are absorbed by the lymphatic system. 3. Migrate to secondary lymphoid structures (nodes, spleen) that are rich in B and T cells. 4. Activate the adaptive immune response by presenting antigen to naïve lymphocytes.
APCs also activate the complement system (→ cell-lysing proteins, NK cells, perforin pores).
The two-sentence summary the professor emphasizes: > 1. The initiation of an acute inflammatory response is the primary function of the innate response. > 2. APCs (macrophages/dendritic cells) transport the pathogen’s genetic material to the secondary lymphoid structures to select B and T cells — the bridge between innate and adaptive immunity.
Innate immune response summary (the cascade): macrophage/dendritic activation + chemical response → ↑ vascular permeability → WBC (neutrophil) infiltration → local signs of inflammation → elevated systemic inflammatory markers → activation of adaptive response via APC.
☐ Can I speak to it? Can I trace a pathogen fragment from a dendritic cell, through the lymphatics, to a naïve B/T cell in a node?
🔗 Cross-module: This is the lymphatic pathway from the last module — APC rides the afferent lymphatics into the node. The “nodes flag infection and mutations” point previewed in the Lymphatic lecture pays off here.
Adaptive = specific, targeted, memory-forming, beginning > 12 hours after innate. Two arms: humoral (B-cell) and cell-mediated (T-cell).
APC macrophages/dendrites absorbed by lymphatics → fluid travels through lymph nodes (activates adaptive) → fluid with APC → spleen → filters blood → robust specific response. Secondary lymphoid structures hold naïve B and T cells → antigen presentation → activation of the antigen-specific cell.
| Clonal selection | Clonal expansion |
|---|---|
| APC finds the B/T cell whose receptor matches the antigen, in secondary lymphatic tissue (nodes) | The selected antigen-specific cell undergoes mass production |
| Selected cell moves to a region where cells proliferate | Occurs in “dark zones”; progeny released into lymph + bloodstream |
The process is the same for T-cells as for B-cells.
Immunoglobulins (antibodies) — the three to know: | Ig | Role | |—|—| | IgG | Major antibacterial/antiviral antibody | | IgM | Initial immune response; expressed on the B-cell receptor surface | | IgE | Binds mast cells + basophils → allergic response |
(The distinct biochemical properties of each Ig, and the neutralization/opsonization/complement destruction mechanisms, are not on the exam.)
Primary vs. secondary antibody response: first exposure → IgM rises first, then IgG (slow, small). Re-exposure → memory cells drive a faster, larger response (why vaccines and prior infection protect).
The T-cell types: | T cell | Marker | Job | |—|—|—| | T-helper | CD4+ | The most important adaptive cell — required for almost all adaptive responses. Secretes cytokines that activate T and B cells; helps B cells make antibodies, helps macrophages destroy microbes, helps activate cytotoxic T cells. HIV attacks these. | | Cytotoxic T | CD8+ | Destroys virus-infected and tumor cells; implicated in transplant rejection; influences NK cells | | Regulatory T | — | Shuts down the T-cell response as the reaction ends; suppresses autoreactive T-cells (autoimmunity, molecular mimicry) |
Cytotoxic T-cell mechanism: MHC-I is on almost all nucleated cells; an infected cell displays antigen from its genetic material → cytotoxic T-cell induces apoptosis by releasing perforins (pores in the membrane) → granzymes enter through the pores and activate enzymes that disrupt cellular function → apoptosis.
☐ Can I speak to it? Can I distinguish humoral vs. cell-mediated, name what each T-cell type does, and explain the perforin/granzyme killing mechanism? Can I say why HIV (which kills CD4+ cells) collapses the whole adaptive response?
🔗 Cross-module: clonal selection/expansion happens in the node’s B-cell and T-cell zones — the Lymphatic node anatomy again. Antibody = the globulin plasma protein from Hematology.
Aging; sex/hormones; nutrition/malnutrition; environmental pollution; toxic chemicals; trauma; burns; sleep disturbance; concurrent illness (malignancy, diabetes, chronic renal failure, HIV); immunosuppressive medications; hospitalization/surgery/anesthesia; splenectomy; stress/socioeconomic status. Factors that increase pathogen exposure: iatrogenic devices (catheters, tubes, PICC lines, external fixators, prostheses) and sexual practices.
The four the professor highlighted: - Age — by 75, the thymus is mostly fibrous adipose tissue → can’t generate naïve T-cells → less T-cell diversity. - Nutrition — zinc is a cofactor in ~70 enzymatic functions; vitamins A and E also matter. - Sleep — low-grade inflammatory factors appear after just one night’s missed sleep. - Surgery/anesthesia — suppress immune function for up to 1 month; splenectomy diminishes the humoral response.
☐ Can I speak to it? Can I contrast moderate vs. strenuous exercise on immunity, apply the neck check, and list PT precautions for an immunosuppressed patient?
🔗 Cross-module: the exercise-guideline framing mirrors the Hematology exercise thresholds (Hb/platelets). Immunosuppression + surgery links to tissue healing and perioperative PT.
| Concept | Key fact |
|---|---|
| Immune functions | Protect from pathogens · clean up dead cells · inflammatory cascade · distinguish self from non-self |
| Innate timing | First line, 0–6 hr; non-specific; no memory |
| Adaptive timing | > 12 hr after innate; specific; has memory |
| First WBC responder | Neutrophil (up to 80% of WBCs) |
| APC bridge | Dendritic cell/macrophage → lymphatics → secondary lymphoid tissue → activates adaptive |
| Primary lymphoid | Bone marrow, thymus (make B/T cells) |
| Secondary lymphoid | Spleen, lymph nodes, adenoids/tonsils, Peyer patches (select cells) |
| B-cells | 25% of lymphocytes; humoral; extracellular; plasma + memory |
| T-cells | 70% of lymphocytes; cell-mediated; intracellular |
| CD4+ T-helper | Most important adaptive cell; HIV target |
| CD8+ cytotoxic T | Kills infected/tumor cells via perforin + granzyme |
| NK cells | 5% of lymphocytes; innate; kill virus/tumor cells with perforins |
| Key immunoglobulins | IgG (antibacterial/antiviral) · IgM (initial) · IgE (allergy) |
| Cardinal signs | Rubor · Calor · Tumor · Dolor |
| Leukocytes (normal) | 5.0–10.0 ×10⁹/L |
| Leukocytosis | > 11.0 ×10⁹/L |
| Leukopenia | < 4.0 ×10⁹/L |
| Neutropenia | < 1.5 ×10⁹/L; moderate 0.5–1.0; severe < 0.5 |
| Phases of infection | Incubation → Prodromal → Invasion → Convalescence |
| Viral invasion | Attach → penetrate → uncoat → replicate → assemble → release |
| Epidemiology | Incidence (new) · Prevalence (all) · Endemic · Epidemic · Pandemic |
Not on the exam (per professor): hematopoiesis diagram · NK activating/inhibitory receptor detail · immunoglobulin biochemical properties · antibody destruction mechanisms (neutralization/opsonization/complement) · the full pro-inflammatory cytokine list (IL-1, IL-6, IL-8, etc.).
| Shared concept | Where it shows up | Why it bridges |
|---|---|---|
| APC → lymphatics → nodes/spleen | Immune ↔︎ Lymphatic | The adaptive response literally runs on the lymphatic pathway you already studied |
| Nodes flag infection & mutations; spleen filters blood | Lymphatic → Immune | Node/spleen functions previewed there are the activation sites here |
| WBCs, hematopoiesis, spleen, bone marrow | Hematology ↔︎ Immune | Shared cell lineages and lymphoid organs; WBC differential |
| ↑ capillary permeability → interstitial fluid → swelling | Fluid Dynamics → Immune | Inflammation reuses the edema mechanism |
| Prostaglandins / arachidonic acid | Immune → Pharmacology / Tissue Healing | Target of NSAIDs (COX) and glucocorticoids (phospholipase A₂) |
| Antibodies = globulins | Hematology → Immune | Plasma-protein globulins are the immunoglobulins |
| Exercise guidelines by cell/marker | Hematology (Hb/platelets) ↔︎ Immune (NK/neutrophils) | Same “moderate helps, extremes harm” PT framing |
Work these in your own words — they mirror the deck’s Think-Pair-Share prompts and your professor’s “how is X related to Y?” style.
Source: “Immune System” lecture deck (E. Schaumberg, PT, MS, DPT, PhD). Notes structured to your professor’s objective-by-objective, “can-I-speak-to-it” method. Items the professor flagged as not on the exam (hematopoiesis diagram, NK receptor detail, immunoglobulin biochemistry, antibody destruction mechanisms, the full pro-inflammatory cytokine list) are retained for context but marked so you can prioritize.