BIO 446L 1st Edition Lecture 24 Outline of Last Lecture I. Circulatory system 3- blood and hemopoiesis contda. Homopoiesisb. Erythropoiesisc. leukopoeisisi. granulopoeisisii. neutrophilsiii. monocytes and agranulocytesd. thrombopoiesisII. immune systema. lymph and vesselsb. components of lymph tissueOutline of Current Lecture I. Immune System contda. Lymphocytesi. B, T, and NKii. Lymphoid nodulesb. Thymus glandi. T cellsc. Lymph nodesi. Cortex and paracortexd. Spleeni. Red and white pulpii. Stave cellse. MHC’si. MHC Iii. MHC IIf. Immune responsei. Co-stimulation of T cellsii. Co-stimulation of B cellsCurrent LectureImmune System contd- 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.o Regulatory lymphocytes produced in bone marrow-- B, T, and NK B and T- Once in blood, still very immature, go to different locations to reach maturity in several steps as they become more specifico Naïve cells= do not have specific receptors- Once mature, will return to blood to recirculate- T cells—migrate to thymus to mature, cell-mediatedo CD4—helper T cellso CD8—cytotixic T cells- B cells—return to bone marrow to mature, humoral immunityo Express B cell receptors NK cells- Less specific, tend to attack bacteria and cancer cellso Lymphoid nodules= primarily B lymph, also some helper T cells Cells become activated in germinal centers- naïve B cells are presented with antigens at lymphoid nodules- in concert with helper T recognition, causes naïve B cell receptors to alter gene expression of receptors to be specific to the antigen- Thymus glando Mediastinumo Loaded with T lymphocyteso Tissue divided into lobules Cortex—outer, jammed with lymphocytes Medulla—inner, less denseo Lymphatic epithelial cells Bigger than lymphocytes These lymphocytes are APCs T cells are continuing development here- Adult thymus is thus very sparse because they have reached maturityo Positive selection In cortex Cytokines released by epithelial cells will stimulate T lymph to express CD markers and receptors Antigens are then presented to them and recognize CD markers Only antigens recognized are attached to MHC protein on antigen presenting cells (APC)o Negative selection APC displaying self or nonself antigens on MHCs- This is a test of maturity-- Want to only recognize nonself antigens- Lymphocytes must pass this test of proper recognition before allowed to move into the blood and do its job as a mature cell- See chart fpr steps of T maturationo MALT Component found in lymphoid tissue of dendritic cells, B cells, IgA cells, APCs, and lymohoid nodules Stratified epithelia Tonsils are MALT- B cells are becoming activated- Lymph tissue is jammed with lymphocytes- Lymph nodeso Only structure that filters lympho Lymph vessels bring lympho Lymph node structure Cortical space has lymph nodules Filtered lymph collected in medullary sinus of medulla B cells in cortex T cells mostly in paracortex- Paracortex venules lined with high endothelial cells—allow transit and recirculation of lymphocytes- Spleeno Filters bloodo Capsule with extensions into spleen, lobuleso Pulp Red pulp—largely distributed throughout White pulp—more isolated, mostly B cellso Blood sampled from trabecular artery and goes to central arteriole Foreign objects trigger attack- Evokes secretion of antibodies T cell sheath around central arteriole going from trabecular artery to germinal center o Spleen endothelia are very large, stick out into lumen of sinusoid (stave cells)o Removal of old, damaged red blood cells by phagocyteso Stave cells Longitudinal to sinusoid Sinusoid reticular fibers anchor staves to sinusoid Central arteriole distributes red blood cells into red pulp if not normal- Normal if can fit between staves to be recirculated- MHCso MHC I All nucleated cellso MHC II B cells and macrophageso Markers are unique to organisms—basis for organ matcho MHC I with antigen—active T cell will killo MHC II  Occurs in response to bacterial infection Phagocytose- Vesicle with MHC II and antigen fuse with lysosome to signal immune system for a full scale attack- Immune responseo Co-stimulation of T cells  Helper CD4- An APC presents antigen to naïve helper T cell- Release cytokines from helper T and APC- T cell receptor will recombine genes of receptor site to become specific Cytotoxic CD8- An APC present antigen to naïve cytotoxic T cell- Helper T clones that recognized antigen to stimulate recombination of receptor site to specify and then attack MHCIo Co-stimulation of B cells B cells- APC precents antigen to naïve B cell- Activates receptor expression- Helper T cell with MHC II and antigen that activates B cell will stimulate B cell to recombine receptor site to specifyo Cells will divide—plasma cells (produce antibodies) and memory B cells are