This document defines key terms related to disease transmission and the immune system. It explains that pathogens can transmit diseases through direct or indirect contact. The body has mechanical, chemical, and cellular defenses against pathogens, including white blood cells that distinguish self from non-self and produce antibodies. Vaccination exposes the body to harmless antigens to trigger antibody production and develop immunological memory for long-term protection. Both active and passive immunity are described, with active immunity resulting from infection or vaccination and producing memory cells, while passive immunity involves acquiring antibodies without memory cell development.

1. Diseases and
immunity

2. LO:
• Define the key words:
– Pathogen
– Transmissible disease
– Active immunity
– Passive immunity
• Explain the process of vaccination
• Explain the specificity of antigens
• State the types of body defence

3. Pathogen = Disease causing organism

4. Transmissible disease
• Is a disease in which the pathogen can be
passed from one host to another
Diseases can be transmitted:
• direct contact, e.g. through blood or other
body fluids,
• indirectly, e.g. from contaminated surfaces or
food, from animals, or from the air

6. Defence systems
• Mechanical barriers:
- skin and hairs in the nose
• Chemical barriers:
– mucus and stomach acid
• Cells:
– phagocytosis and antibody production by white
blood cells
can be enhanced by vaccination

8. • Discuss the importance of:
– hygienic food preparation,
– good personal hygiene,
– waste disposal and
– sewage treatment
in controlling the spread of disease

9. White blood cells
: phagocytes, lymphocytes
– Distinguish between self and non-self cells
– Produce antibodies
• Molecules on the surfaces of cells that are not found
in other organisms = antigens (e.g. blood system)
• The response of lymphocytes to the presence of a
foreign antigen = immune response

10. • Lymphocytes
– Produce antibodies; memory cells
– antibodies lock on to antigens leading to direct
destruction of pathogens, or marking of
pathogens for destruction by phagocytes
– each pathogen has its own antigens, which have
specific shapes, so specific antibodies which fit the
specific shapes of the antigens are needed
• Phagocytes
– phagocytosis

12. • Memory cells
– Remain circulating in the body for a long time
– If the same antigen is reintroduced a few weeks or
months later, memory cells divide rapidly and
develop into plasma cells
– Basis of immunological memory
– Last for many year, lifelong,

13. Phagocytosis

15. Immunity

16. • Active immunity
– defence against a pathogen by antibody production in
the body
– is gained after an infection by a pathogen, or by
vaccination
• Passive immunity
– short-term defence against a pathogen by antibodies
acquired from another individual, e.g. mother to
infant
– No memory cells are produced
– Important for new-borns: get all antibodies from the
mother

17. Vaccination
process of vaccination:
• harmless pathogen given which has antigens
• antigens trigger an immune response by
lymphocytes which produce antibodies
• memory cells are produced that give long-
term immunity

18. Autoimmune diseases
• some diseases are caused by the immune
system targeting and destroying body cells
• Type 1 diabetes