Vaccine Education Module: The Immune System Updated: February 2015

Roles of the Immune System The immune system protects the body by: Recognizing the presence of infection Containing the infection and working to eliminate it Regulating itself so it does not damage the body Remembering pathogens to prevent diseases from recurring

Components of the immune system Dynamic communication network made up of: Cells Tissues Organs

Organs of the Immune System Spleen Peyer’s patches Appendix Bone marrow Tonsils Adenoid glands Thymus Lymph nodes Lymphatic vessels

Pathogens Organisms that can cause disease: Bacteria Viruses Parasites Fungi Most pathogens are so small that they must be viewed with a powerful electron microscope. Due to their microscopic size, these organisms are called microscopic. The study of microscopic organisms is called microbiology.

Example of a Type of Bacteria This colorized scanning electron micrograph depicts Legionella pneumophila, the bacteria that causes Legionnaires’ disease. Example of a Type of Bacteria Courtesy CDC, Public Health Image Library (PHIL)

Example of a Type of Bacteria This scanning electron micrograph (SEM) shows a strain of Staphylococcus aureus bacteria taken from a vancomycin intermediate resistant culture (VISA). Example of a Type of Bacteria Courtesy CDC

Influenza virus Influenza Virus Photo Credit: Cynthia Goldsmith, CDC

Measles Virus Photo Credit: Cynthia Goldsmith, CDC

Five Types of White Blood Cells Neutrophils: Phagocytose bacteria and fungi Eosinophils: Kill parasites, destroy cancer cells and are involved in allergic reactions Basophils: Release histamine and act in blood clotting Monocytes: Become macrophages; digest dead or damaged cells and pathogens Lymphocytes: Two major classes of these white blood cells T cells B cells

White Blood Cells Courtesy CDC, PHIL This stained photomicrograph revealed a number of white blood cells otherwise known as leukocytes. These cells are part of the body’s antibody-mediated response, fighting the constant onslaught of pathogenic invaders such as bacteria and foreign debris. White Blood Cells Courtesy CDC, PHIL

White Blood Cell Courtesy CDC, PHIL This scanning electron micrograph (SEM) depicted a number of red blood cells magnified 7766x. The cell in the center displaying a knobby surface is a white blood cell. White Blood Cell Courtesy CDC, PHIL

T Cells Activate B cells to produce antibodies Activate macrophages to destroy antigens that have been tagged by antibodies Kill our own cells that are infected with viruses

B Cells Produced in the bone marrow Primary role is to produce antibodies

Antibodies Y-shaped molecules with two distinct regions Constant region Variable region allows different antibodies to recognize different antigens

Antibodies Proteins that neutralize antigens and prepare them for destruction by phagocytes Programmed to recognize and bind to the antigen so that it can be destroyed Activate a group of proteins called complement, which assist in killing pathogens