Introduction in serology Dr. Dalia Galal Hamouda

First line of defense Second line of defense Inborn or innate immunity (non specific): It is present at birth. This is our First Line Of Defense. It is generally effective against a variety of infections.  Acquired (adaptive) or specific immunity: It is not present at birth but generally acquired after exposure to the infecting particles or cells. Specific for one type of  infection Second line of defense

Cells Involved in Immunity Natural killer

T cells Denderitic cells B cells

Important components of innate immunity Factors that limit entry of microorganisms into the body Factor Mode Of Action -Keratin layer of intact skin -Acts as mechanical barrier -Lysozyme in tears and other secretions -Degrades peptidoglycan in bacteria cell wall -Respiratory cilia -Elevate mucus containing trapped organisms -Low pH in stomach and vagina; -Retards growth of microbes fatty acids in skin -Surface phagocytes -Ingest and destroy microbes (eg. alveolar macrophages) -Defensins (cationic peptides) -Create pores in microbial membrane -Normal flora of throat, colon -Occupy receptors which prevent and vagina colonization by pathogens

Important components of innate immunity Factors that limit growth of microorganisms within the body Kill virus infected cells Ingest and destroy microbes Ingest and destroy microbes, and present antigen to helper T-cells Inhibit viral replication C3b is an opsonin, membrane attack complex creates holes in bacterial membranes Sequester iron required for bacterial growth Elevated temperature retards bacterial growth Limits spread of microbes Natural killer cells Neutrophils Macrophages and dendritic cells Inferons Complement Transferrin and lactoferrin Fever Inflammatory response

Important components of adaptive immunity B Lymphocytes and T lymphocytes B lymphocytes (B cells) mature in the bone marrow. B lymphocytes have receptors (antibodies) attached to their surface which function to detect antigens. There is only one specific kind of receptor on the surface of a lymphocyte. A single B lymphocyte can therefore detect only one kind of antigen. Our bodies have millions of different kinds of B lymphocytes. T lymphocytes (T-cells) are lymphocytes that mature in the thymus. This type of immunity is used to fight cells such as cancer cells, virus-infected cells, single-celled fungi, parasites, and cells of an organ transplant.

B cells T cells

Antigens and Antibodies Antigens are molecules that stimulate antibodies which are capable of being recognized. They are usually a protein or carbohydrate chain. The body can recognize bacteria and viruses as being foreign because they have antigens on their surface which are different than the bodies "self" antigens. Antibodies are proteins that protect against foreign invaders, either foreign molecules, viruses, or cells. Antibodies are produced by B lymphocytes. They are capable of recognizing specific particles due to their shape. Their ability to recognize foreign shapes makes them useful in defending against foreign invaders. Antibodies are Y-shaped molecules with a constant region and two binding sites that vary from one antibody to the next. Antibodies fit together with and bind with antigens like a lock and key. The body does not produce antibodies that bind to its own (self) antigens. Therefore all particles that are bound to antibodies are foreign.

Important features Of Innate and Acquired (adaptive) Immunity Type of Immunity Specificity Effective immediately Improves Has after exposure to After Exposure memory microbe Innate Nonspecific Yes in No No minutes Acquired Highly No--requires Yes Yes specific several days before becoming effective

Organs of the Immune System 1. Primary lymphoid organs Bone Marrow Largest tissue of the body Main source of hematopoietic cells. Lymphocyte stem cells released from marrow and travel to primary lymphoid organs for maturation: T cells go to Thymus, B cells mature in bone marrow. Thymus Ductless gland-like structure located beneath the sternum (breastbone). Lymphocyte stem cells develop into T lymphocytes under the influence of thymic hormones.

2. Secondary lymphoid tissue From the primary lymphoid organs, B and T lymphocytes migrate to the peripheral secondary lymphoid organs. 1) They encounter antigens and are transformed into an activated state. 2) They become effectors of the humoral or cell-mediated immunity. Spleen It is the body's largest reservoir of mononuclear-phagocytic cells. Both T and B lymphocytes are present but they are segregated. The red pulp of the spleen consists of blood vessels lined with macrophages. White pulp contains lymphoid tissue. Also functions as a filter by removing effete cells from circulation. Lymph nodes Located in several areas of the body, including the neck and those points where the arms and legs join the trunk of the body. They serve as a filter for the tissue fluid or lymph. Lymph is a collection of tissue fluid flowing from the limbs and tissues through the lymph nodes on its way to the blood stream.

Examples of other Secondary Lymphoid Tissue or organs Gut associated lymphoid tissue Tonsils Bronchus associated lymphoid tissue Mammary glands Salivary glands

Overview of the Immune Response