Defence mechanisms

• What are the defence mechanisms of the human body against disease?

  Physical and chemical defences
• What happens if the body's defence mechanisms fail?

  Organisms may become overwhelmed and die
• What occurs when the body overcomes a pathogen?

  The pathogen is destroyed and immunity develops
• What are the two types of defences in the human body?

  Physical and chemical defences
• How do physical defences differ from chemical responses?

  Physical defences are general and non-specific
• What is phagocytosis classified as?

  A general chemical response
• What type of white blood cells are involved in specific immune responses?

  Lymphocytes
• What are the two types of lymphocyte responses?

  Cell-mediated and humoral responses
• Which lymphocytes are involved in cell-mediated responses?

  T-lymphocytes
• Which lymphocytes are involved in humoral responses?

  B-lymphocytes
• How do human cells recognize self or foreign cells?

  Using molecules on their surface
• What types of substances do human cells recognize?

  Pathogens, non-self material, toxins, abnormal cells
• Why is it important for cells to recognize foreign substances?

  To minimize the threat they pose
• What issue can arise for organ transplant patients?

  Recognition of transplanted organs as foreign
• Are lymphocytes produced in response to an infection?

  No, they already exist
• What happens when a pathogen is detected by lymphocytes?

  Lymphocytes recognize and divide to increase numbers
• What is the process called when lymphocytes increase in number?

  Clonal selection
• How do lymphocytes recognize self cells during the fetal stage?

  They only collide with self antigens
• What happens to lymphocytes that fit self cells?

  They are killed or suppressed
• What is the outcome for lymphocytes that do not fit self cells?

  They remain and respond to foreign material
• What happens to lymphocytes in adults that show an immune response?

  They undergo apoptosis before maturing