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Defence, immunity and vaccination explained

Infection and response • Communicable diseases

Key concepts

What you'll likely be quizzed about

  • The skin acts as a continuous barrier that prevents pathogen entry and secretes antimicrobial compounds that eliminate some microbes.
  • Dead outer skin cells shed and remove attached pathogens.
  • Tears and saliva contain lysozymes that chemically dismantle bacterial cell walls and provide local immunity in the eyes and mouth.
  • Hairs and mucus in the nose trap inhaled particles and pathogens; swallowing transfers trapped material to the stomach where acid destroys many microbes.
  • Ciliated epithelial cells in the trachea and bronchi propel mucus up the airways, enabling trapped pathogens to move to the throat for swallowing, thus preventing lung infections.

Flashcards

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How do antibodies help clear infections?

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Antibodies bind to specific antigens, causing pathogens to clump and marking them for destruction by phagocytes.

Key notes

Important points to keep in mind

First-line defences are non-specific barriers: skin, mucus, cilia, and stomach acid.

Phagocytes perform non-specific engulfment; lymphocytes perform specific antibody and memory responses.

Antibodies bind antigens, clumping pathogens and aiding phagocytosis; antitoxins neutralise toxins.

Vaccines expose the immune system to antigens without causing disease and produce memory lymphocytes.

Herd immunity requires high coverage and sustained uptake to effectively interrupt transmission.

Global vaccination success relies on logistics, funding, and maintaining public confidence; low uptake risks disease resurgence.

Antigenic variation and immunosuppression limit immune protection and vaccine impact.

Boosters restore waning immunity and maintain effective memory cell levels.

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