Basic Immunology

Basic Immunology • OBJECTIVE • To provide the fundamentals of the immune response. The immune response is the host reaction to infection/invasion. It is important to understand the immune response when developing materials and devices to be implanted into the body. CHEE 340

Background : Cell Communication Cells can communicate to each other through the use of soluble chemicals, contacts and cell membrane resident receptors. CHEE 340

Intravascular Cells • white blood cells Granulocytes neutrophil eosinophil basophil lymphocyte monocyte CHEE 340

Host Defence • The body is under constant attack by microorganisms in the environment. • pathogen : an infectious agent that causes disease • Infectious disease occurs when a microorganism succeeds in evading or overwhelming host defenses to establish a local site of infection and replication. In order for a pathogen to enter the body it must first overcome the epithelium and then the innate immune response and the adaptive immune response. CHEE 340

First Line of Defence • Epithelial Tissue • covers the whole surface of the body • made up of closely packed cells • can be divided into simple or stratified • interior epithelium covered with a mucus layer CHEE 340

Stratified Epithelium - Skin CHEE 340

Innate Immune response • If a pathogen breaches the epithelium, • then the innate immune response begins. • The cells of the immune system determine • “self” from “non-self” by recognizing molecules on the microbe surface. • Macrophages and dendritic cells are immune cells (phagocytes) that reside within the tissue. Neutrophils are phagocytes that reside in the blood but can extravasate into tissue during inflammation. • There are circulating proteins, called complement, that either kill microbes or mark them for effective phagocytization. CHEE 340

Phagocytosis • Phagocytosis: • Engulfing and degradation or digestion of fragments of tissue or material • long membrane evaginations, called pseudopodia. • Ingestion forming a "phagosome," which moves toward the lysosome. • Fusion of the lysosome and phagosome (phagolysosome), releasing lysosomal enzymes • Digestion of the ingested material. • Release of digestion products from the cell. CHEE 340

Inflammatory Response • Pathogen recognition and tissue damage begin an inflammation response. This is characterized by : • swelling • pain • redness • heat • Inflammation allows for neutrophil and plasma protein extravasation. Both of these effects aids the immune response. CHEE 340

Diapedesis Movie CHEE 340

Phagocytosis Movie CHEE 340

Adaptive Immune Response • The innate response triggers the cells of the adaptive immune response called lymphocytes. Lymphocytes are present in the blood and in the lymphatic system. CHEE 340

Antigen Presenting Cells • Dendritic cells and macrophages digest invading microbe and then present the antigen of the microbe to lymphocytes in lymphoid organs. CHEE 340

Activation of T cells CHEE 340

Activation of B cells The role of B cells is to produce antibodies. CHEE 340

Antibody CHEE 340

Summary • The immune system consists of : • biological barriers • the phagocytic cells within tissues • proteins in circulation called complement • the lymphatic system • lymphocytes such as B and T cells • antibodies CHEE 340

Basic Immunology