Host defence against bacteria, viruses, fungi and parasites
Which arm of immunity controls each class of organism, so that the infection a patient gets points to the defect they have, from asplenia and complement deficiency to CD4 lymphopenia, neutropenia and Th17 failure.
Tier 1Medical sciences concept
Written with AI assistance and fact-checked against the sources below. For exam study, not clinical decisions. How notes are made
At a glance
- Each class of organism is controlled by a particular arm of immunity. The infection a patient gets tells you what is broken.
- Extracellular bacteria: antibody, complement, neutrophils and spleen.
- Intracellular bacteria and mycobacteria: Th1 cells, IFN-γ and activated macrophages.
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Sources
- Janeway's Immunobiology (10th ed.)W. W. Norton (Murphy and Weaver, 2022), 2022
- Mandell, Douglas and Bennett's Principles and Practice of Infectious Diseases (9th ed.)Elsevier (Bennett, Dolin and Blaser, 2020), 2020
- Australian Immunisation Handbook: vaccination for people with asplenia or hyposplenia, and for people with complement deficiency or on complement inhibitorsAU/NZAustralian Government Department of Health, Disability and Ageing, 2026
- Therapeutic Guidelines: AntibioticAU/NZTherapeutic Guidelines Limited, 2025
- Singer M et al. The Third International Consensus Definitions for Sepsis and Septic Shock (Sepsis-3). JAMA 2016;315:801-10JAMA, 2016
- Bastard P et al. Autoantibodies against type I IFNs in patients with life-threatening COVID-19. Science 2020;370:eabd4585Science, 2020
- Last updated
- 14 November 2026
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