Immunology Lecture 3 PDF

BCHEM 471 Immunology Alexander Kwarteng, PhD Lecture three Dr. Alexander Kwarteng || Department of Biochemistry & Biotechnology, College of Science, KNUST  Dr. A. Kwarteng...

BCHEM 471 Immunology Alexander Kwarteng, PhD Lecture three Dr. Alexander Kwarteng || Department of Biochemistry & Biotechnology, College of Science, KNUST  Dr. A. Kwarteng T & B Cell Development Dr. Alexander Kwarteng || Department of Biochemistry & Biotechnology, College of Science, KNUST  Word/Terms List Activation Differentiation Double negative cells Double positive cells Effector cells Maturation Negative selection Positive selection Dr. Alexander Kwarteng || Department of Biochemistry & Biotechnology, College of Science, KNUST  Lymphopoiesis T cell progenitors originate in the BM (~50million per day) Migrate to thymus Characteristic surface marker and genetic/intracellular changes 90% never make it to maturity, i.e. only 10% do Apoptosis hits those that do not have functional TCR or don’t get ”selected” Dr. Alexander Kwarteng || Department of Biochemistry & Biotechnology, College of Science, KNUST  Lymphopoiesis T cell generation slows down with age Mature T cells may divide in secondary lymphoid organs What is consequence of that? Dr. Alexander Kwarteng || Department of Biochemistry & Biotechnology, College of Science, KNUST  T Cell Maturation Hematopoietic stem cells(HSC) Lymphoid stem cell (progenitor) Circulating lymphoid stem cells Thymocytes Dr. Alexander Kwarteng || Department of Biochemistry & Biotechnology, College of Science, KNUST  T cells develop in the thymus T cells (T-lymphocytes) = thymus-dependent lymphocytes The thymus is a primary lymphoid organ because it is only involved in development, not fighting infection. The thymus contains a) Thymocytes (immature T cells) b) Thymic stroma (epithelial cells) Dr. Alexander Kwarteng || Department of Biochemistry & Biotechnology, College of Science, KNUST  The Thymus 2 areas of the thymus: Cortex – outer, close-packed consists of ectodermal cells; can contain thymocytes and macrophages Medulla – inner, less dense consists of endodermal cells; contains thymocytes, dendritic cells, and macrophages Thymic anlage : The combination of the ectodermal and endodermal cells, colonized by progenitor cells from the bone marrow. Dr. Alexander Kwarteng || Department of Biochemistry & Biotechnology, College of Science, KNUST  Thymus facts Fully developed at birth and increases in size until puberty Most active in the young Degrades after puberty (involution), being replaced with fat tissue Even after involution (~30 yrs. old) or a thymectomy immunity by T cells is not impaired significantly Mature T cell repertoire is long-lived and self- renewing Dr. Alexander Kwarteng || Department of Biochemistry & Biotechnology, College of Science, KNUST  T Cell Maturation Young thymocyte (T cell precursor) Double negative thymocytes Double negative with early TCR expression Double positive with TCR expression Naïve CD4 and CD8 T cells Dr. Alexander Kwarteng || Department of Biochemistry & Biotechnology, College of Science, KNUST Dr. Alexander Kwarteng || Department of Biochemistry & Biotechnology, College of Science, KNUST  Thymic Selection Positive selection Double positives bind MHC molecules Nonbinders die Binders become single positives Dr. Alexander Kwarteng || Department of Biochemistry & Biotechnology, College of Science, KNUST  Thymic Selection Negative selection CD4 or CD8 cells that survive positive selection may react or bind to self MHC alone with high affinity or with Self MHC-self Ag complexes These cells are programmed to die Nonbinders survive Dr. Alexander Kwarteng || Department of Biochemistry & Biotechnology, College of Science, KNUST Dr. Alexander Kwarteng || Department of Biochemistry & Biotechnology, College of Science, KNUST Dr. Alexander Kwarteng || Department of Biochemistry & Biotechnology, College of Science, KNUST  B Cell Production and development Dr. Alexander Kwarteng || Department of Biochemistry & Biotechnology, College of Science, KNUST  B-CELLS… Origin… Development… SelectionS ActivationS Progenitor B cells (pro-B-cells) bearing a CD45R marker develop – in the bone marrow – into immature and then mature B cells. Then, they migrate to peripheral lymph nodes. Those developmental events are physically and physiologically distinct; the former are antigen independent; the latter are antigen dependent. Dr. Alexander Kwarteng || Department of Biochemistry & Biotechnology, College of Science, KNUST Dr. Alexander Kwarteng || Department of Biochemistry & Biotechnology, College of Science, KNUST  Cytokines of various types are secreted by T-helper cell and are received by differentiating B-cells. The various cytokines affect what immunoglobulin isotypes will be produced by plasma cells. Dr. Alexander Kwarteng || Department of Biochemistry & Biotechnology, College of Science, KNUST Where is activation happening? And what is happening? The primary response is initiated in the paracortex. T-cells respond to processed antigen that is typically delivered from a site of origin by dendritic cells. B-cells see the same antigen in an unprocessed form in the lymph. Dr. Alexander Kwarteng || Department of Biochemistry & Biotechnology, College of Science, KNUST  QUIZ 2 1. Any substance which is capable of inducing an immune response is referred to as an antigen True b) False 2.The transcriptional factor for Th1 cells is called………….. 3. The signature molecule of Th17 response is…………….. 4. Which of the following cells produce antibodies? T cells b) dendritic cells c) monocytes d) plasma cells 5. Interleukins are proteins which help cell to cell communication True b) False 6. Toll-like receptors are glycoproteins used to recognize ………………on the surfaces of ……………… 7. Give 2 examples of Toll-like receptors 8. Give 2 features of an immunogen 9. Differentiate between MHCI and MHCII molecules 10. Granzymes are normally (percentage wise) produced by activated CD8+ T cells. What is the function of this molecule? Dr. Alexander Kwarteng || Department of Biochemistry & Biotechnology, College of Science, KNUST