Key Conceptual Connections in BIO-01

Connection 1: Malaria ↔ RBC Biology

• Plasmodium invades RBCs → destroys them → severe anaemia
• RBC haemoglobin → haemozoin (toxin) when parasitized → fever
• P. falciparum infects all RBC ages; P. vivax only reticulocytes → different severity

Connection 2: HIV ↔ All of Immunity

• HIV destroys CD4+ T-HELPER cells (the coordinators)
• Loss of T-helper cells → impaired humoral immunity (B-cells not activated properly) + impaired CMI (cytotoxic T-cells not activated)
• Both arms of adaptive immunity collapse together
• Passive immunity fails long-term without active immunity infrastructure

Connection 3: Cancer ↔ Immunity (Immunosurveillance)

• NK cells and cytotoxic T-cells normally patrol and kill cancer cells (immunosurveillance)
• HIV-positive patients have increased cancer risk (Kaposi's sarcoma, NHL) because CMI surveillance is impaired
• Immunotherapy for cancer = $\frac{restoring}{enhancing}$ this surveillance

Connection 4: Drug Abuse ↔ Neuroscience

• Both heroin and cocaine ultimately affect dopamine reward pathway
• Heroin: mu-opioid receptors → inhibitory → reduces dopamine → CNS depression
• Cocaine: blocks DAT → more dopamine → CNS stimulation
• Both cause addiction because reward circuit is manipulated

Connection 5: Vaccination ↔ Memory Cells ↔ Evolutionary Strategy

• Vaccine exploits the memory cell mechanism of adaptive immunity
• Each vaccine dose = training session; booster = reinforcement
• Memory cells persist via clonal maintenance without continuous antigen
• Herd immunity = when enough people vaccinated, pathogen cannot find susceptible hosts

Connection 6: Innate ↔ Adaptive — The Handshake

• Macrophage eats pathogen (innate) → presents antigen on MHC-II to CD4+ T-helper cells (adaptive)
• This APC-T-cell interaction is the handshake that activates adaptive immunity
• No innate immunity → no activation of adaptive immunity