MICR J210 1st Edition Lecture 8 Outline of Last Lecture 1. Overview of the Body’s Defenses2. General Mechanisms of the Immune System3. Normal Microbiota in Innate Immunity4. Defense Components of Blood5. Phagocytosis6. Nonphagocytic Killing7. The Complement Cascade8. Inflammation9. FeverOutline of Current Lecture 1. Overview of Adaptive Immunity2. Elements of Adaptive Immunity3. Lymph Nodes4. Antigen Provoke a Specific Immune Response5. B Lymphocytes6. Classes of Antibodies7. T Lymphocytes8. Types of T LymphocytesThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.9. Clonal Section Theory10. Diversity of BCR and TCR11. Cytokines12. Preparation for an Adaptive Immune ResponseCurrent LectureOverview of Adaptive ImmunityInvolves activity of lymphocytes• Two main types of lymphocytesB lymphocytes (B cells)Mature in the bone marrow• From the Lymphoid pathwayResponsible for humoral (antibody) mediated response)• Antibodies are derived from the B cells (plasma cells)T lymphocytes (T cells)Mature in the thymus • From the Lymphoid pathwayT cells are produced in the bone marrow and mature in the thymus• There are several different types of T cells (helper or cytotoxic) • T helper cells and cytotoxic cells interact with each other and with the B cells• Cytotoxic cells remove infected tissues or abnormal cells• NK cells hold the fort until the other T lymphocytes can arriveResponsible for cell mediated response• Adaptive immunity is the body’s ability to recognize and defend itself against distinct invaders and their products• Five attributes of adaptive immunitySpecificity: for pathogens onlyInducibility: response can’t happen all the time—takes too much energyClonality (Clonal selection theory): must be able to clone to expand the responseUnresponsiveness to self (tolerance): can’t destroy healthy self cells—only pathogenic onesMemory: must be able to recognize pathogens that have already been encoded forElements of Adaptive ImmunityThe Tissues and Organs of the Lymphatic System• Screen the tissues of the body for foreign antigens• Composed of lymphatic vessels and lymphatic cells, tissues, and organsLymphatic vessels and the flow of lymphOne-way system that conducts lymph from tissues and returns it to the circulatory system via left subclavian veinLymphLiquid with similar composition to blood plasmaArises from fluid leaked from blood vessels into surrounding tissuesLymphatic vessels conduct lymph from tissues and returns it to the circulatory vein (by gravity and muscle contraction) Lymph: plasma without RBC but does have WBCThe Organs of the Lymphatic System• Primary (central) lymphoid organs; where cells undergo maturationRed bone marrowThymus• Secondary lymphoid organs; Where matured cells reside and functionLymph nodesSpleenTonsils (lymph nodes)Mucosa-associated lymphatic tissue (MALT)• MALT-lymph tissue associated with the gut and genital regionsLymph Nodes• Lymph nodes are small, bean-shaped structures in the body that are part of the lymphatic system, which carries lymph fluid, nutrients, and waste material between the body tissues and the bloodstream. • Lymph nodes are found singly or in groups. They may be as small as the head of a pin or as large as an olive. Groups of lymph nodes can be felt in the neck, groin, and underarms.Lymph nodes are common where pathogens are likely to invade…such as the neck and in the intestinesClonal expansion takes place in the lymph nodes• When a part of the body is infected, the nearby lymph nodes can become swollen. For example, if a person has a throat infection, the lymph nodes in the neck may swell andbecome tender.Antigens provoke a specific immune responseProperties of antigens– Molecules the body recognizes as foreign and worthy of attack– Antigen is something that the body recognizes as foreign-viruses, protozoa, bacteria, etc.– They have molecules are their cell surfaces that differ from ours– Recognized by three-dimensional regions called epitopes– Recognized in smaller sections called epitopes (defined by shape)– One antigen may have several different epitopes depending on the shape of the molecule– Antigen will provoke the adaptive immune response– Include various bacterial components as well as proteins of viruses, fungi, and protozoa– Food and dust can also contain antigenic particles- Exogenous antigens are antigens that have entered the body from the outside, for example by inhalation, ingestion, or injection.– Exogenous antigens: enters the body from the outside (often bacteria)- Endogenous antigens are antigens that have been generated within previously-normal cells as a result of normal cell metabolism, or because of viral or intracellular bacterial infection– Endogenous: antigen that has been generated within normal cells (abnormal metabolism, mutations, etc.) common in tumors and cancer but most importantly in viral infected cells. The infected cell makes the viral ribosomes under the coercion of that virus- Autoantigen is usually a normal protein or complex of proteins – Autoantigen: normal cell proteins that have been changedB Lymphocytes- B Lymphocytes (B Cells) and Antibodies– Arise and mature in the red bone marrow – B cells give rise to antibodies– B cells become plasma cells or memory cells– Plasma cells are what give rise to antibodies– Found primarily in the spleen, lymph nodes, and MALT– Small percentage of B cells circulate in the blood– Major function is the secretion of antibodies• Specificity of the B cell receptor (BCR)Each B lymphocyte has multiple copies of the B cell receptor• The antibody that gets produced depends on the specificity of the B cell receptor• B cell receptor is the copy of the antibody that the B cell will make. • The transmembrane region is anchored to the cell membrane and the antibody stick out from there• Every immunoglobulin molecule is identical on a given B cell• Each B cell makes a variable region with random specificityEach B cell generates a single BCR• IgM is bound to the transmembrane portion of the BCR• When an epitope of a pathogen binds to the to antibody, a message is sent to the nucleus of the B cell and that cell is activatedTwo variable regions of the BCR form the antigen-binding sitesEach BCR recognizes only one epitopeThe entire repertoire of an individual’s