Lecture 26Outline of Last Lecture I. The Lymphatic SystemOutline of Current LectureI. The Immune SystemCurrent Lecture1. Immune System (Part 1). a. What is the main cell type of the immune system? i. White blood cells- lymphocytesb. Define antigen. i. Foreign moleculec. Explain the functional differences between B cells and T cells.i. B cells: humoral immune response 1. Antibody secretiona. Antibody: protein molecules that attach to antigens, fit the shape of the antigen molecules ii. T cells: Cell-mediated immune response d. How do plasma cells relate to B lymphocytes? i. As a B-cell starts to make and secrete large amounts of antibodies, it transforms into a plasma celle. Explain the concept of clonal selection. i. Each lymphocyte, T or B, recognizes and attacks just one kind of antigen ii. Reflecting our body’s need to attack the many different types of antigens that infect usf. Explain how lymphocytes patrol the body through recirculation.i. “mobile police force”ii. Constantly move out of the bloodstream at the capillaries and venules to enter loose connective tissue in surrounding areas in search of infectious microorganismsiii. After destroying the microorganism, the lymphocytes re-enter the capillaries and venules and continue circulating in the blood g. Describe all three3 steps in lymphocyte activation.i. stem cell to lymphocyte precursorii. the cells become lymphocytes, T or B1. some of these cells gather in the thymus in the upper thorax à T cells2. identified as B cells while in the bone marrow 3. determined which antigen will be recognized by each lymphocyte, before encountering it4. here it is assured that lymphocytes will not attack the body’s own proteins iii. Final activation, in infected connective tissueBIOL_315 1nd Edition1. Enter the bloodstream, circulate, move through the capillaries and venules to enter infected connective tissue 2. Only when at infection site, finding and binding to its specific antigen, final activation where it can destroy foreign microorganismsh. What are helper-T cells, and how do they relate to AIDS? i. Helper-T cells secrete lymphokine molecules that signal the cytotoxic T lymphocyte or B lymphocyte to divide and differentiate 1. Without helper- T cells lymphocytes cannot be activated ii. Non activation is what happens in AIDS, where the HIV virus selectively eliminates the helper-T cells, weakening the immune system until the patient dies from a variety of infections i. How do antigen-presenting cells (like macrophages) function in the activation of T lymphocytes? i. Binding induces the macrophages to secrete lymphokine molecules, which stimulate the cytotoxic T cell to divide, after division the cells are fully ready to attackj. Contrast effector lymphocytes and memory lymphocytes.i. Effector lymphocytes: fight the infection and soon dieii. Memory lymphocytes: long-lived, basis of acquired and long-term immunity1. as soon as they encounter their antigen, they divide againa. this division is much more rapid and efficient than the first
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