defense in humans

• Animals and plants have innate defenses to protect themselves against pathogens. The human body responds to foreign organisms, especially those that can cause harm. The defense mechanisms of the immune system protect the body from infections and diseases
• Animal defense responses

  First line of defense is the outermost covering of the body, including the skin and mucous membranes lining respiratory tubes, urogenital tracts, and digestive tube. The body uses nonspecific immune system cells that secrete chemicals and proteins to destroy pathogenic microorganisms. The second line of defense, e.g., WBC (phagocytes) and fever, takes action when the first line is breached. The specific immune system can identify and remove pathogenic microorganisms that have evaded the innate immune system. It can aggressively attack and kill any identified foreign cell
• Defense mechanism in human body

  • Nonspecific immunity (innate). 2. Specific immunity system (adaptive) immunity - the ability of the body to defend itself against disease-causing organisms. 3. Humoral immunity - the ability to produce antibodies
• Antibodies/Immunoglobulins


  • Proteins produced from circulating lymphocytes that can ward off foreign substances. They recognize and bind to antigens, leading to destruction. This type of immunity is a genetic predisposition received from parents and ancestors
• Types of immunity


  • Inborn immunity
  • Acquired immunity
• Antibodies can be obtained when exposed to antigens, either naturally or artificially. Acquired immunity progresses from birth
• Acquired immunity


  Occurs when a person is exposed to a live pathogen, develops the disease, and becomes immune as a result of the primary immune response. This can happen in active or passive form
• Forms of acquired immunity

  • Naturally acquired immunity
  • Artificially acquired immunity
• Type of acquired immunity

  • Occurs when the person is exposed to a live pathogen, develops the disease, and becomes immune as a result of primary immune response
• Types of acquired immunity

  • Naturally acquired immunity
  • Artificially acquired immunity
• Artificially acquired immunity


  1. Can be in active or passive form

  2. Introduced through a vaccine containing antigens

  3. Vaccine booster shots may be needed for long-term immunity
• Active immunity


  Obtained once a person comes in direct contact with a disease providing permanent immunity
• Passive immunity


  Obtained during fetal development through mother's placenta and by breastfeeding, lasting for a short period of time
• Types of antibodies/immunoglobulins


  • IgG
  • IgA
  • IgM
  • IgD
  • IgE
• IgG


  • Mainly present in circulation, major form of antibody in blood plasma, produced in a secondary immune response, can cross the placenta from mother to fetus
• IgA


  • Exists in bodily secretions, attaches to antigens to prevent them from reaching the bloodstream
• IgM


  • Found circulating in the body, first to encounter pathogens reaching the bloodstream
• IgD


  • Signifies antigen-antibody type differentiation, attached to the surface of B-cells, part of the body's adaptive immune system
• IgE


  • Plays a big role in allergic reactions, stimulates the release of histamines during allergic reactions
• Vaccination is the process of introducing an attenuated or weakened antigen in a susceptible host for the purpose of increasing immunity against a particular infectious agent