T Cells:Adaptive/Specific Immunity

1. T Cells:Adaptive/Specific Immunity Immunity

2. Review of B cells • B cells fight antigens by producing antibodies • Fights antigens floating around your body

3. T-Cells • Start from hemapoietic stem cells in bone marrow • Travel to thymus to mature • Thymus: organ above heart • DOES NOT secrete antibodies http://www.mdausa.org/images/qpix/q44thym3.jpg

4. Two types of T cells • Helper T Cells • CD4+ cells • Secrete signaling proteins “cytokines” • Stimulate other cells • Cytotoxic T cells • CD8+ cells • Recognize cells infected with viruses and kill them

5. T Cells have Cell surface Receptors • T-Cells patrol the body cells • Have receptor proteins on surface • Receptors look like B-Cell’s receptors • Recognize specific shapes of antigens presented by molecules called MHC molecules

6. Every Body cell has MHC molecules • MHC: Major Histocompatability Complex • Area of genes on chromosome 6 • A protein found spanning cell membranes • Two types • Class I MHC • Encoded by HLA-A, HLA-B, and HLA-D • On every cell • Encoded by HLA • Class II MHC • Encoded by HLA-D genes • Only on B cells and macrophages

7. MHC must match for Organ Donation • MHC genes complex most polymorphic KNOWN to man • Many alleles for same genes • Thousands of different combinations • In a study of 1000 individuals • Only 111 people had 1 match in group • Their job is to show all the proteins in the cell

8. MHC presents peptides • ALL proteins in a cell are broken down • By a proteosome into pieces(peptides) • Normal proteins • Foreign proteins • Peptides are presented on cell surfaces by MHC • MHC has a groove like a bun • Peptide is hot dog that fits inside http://www.mdausa.org/images/qpix/q44molecule1.jpg

9. 1st type: T helper Cells • T helper cells • CD4+ cells • recognize a viral protein presented by MHC II • Help to activate macrophages and B-cells • MHC II is only found on macrophages and B-Cells • EX. Macrophage eating salmonella bacteria

10. 1st type: T helper Cells • Macrophage ingest bacteria and break down proteins • Present on surface with Class I MHC molecules • T-helper cells bind the antigen-MHC complex • Releases cytokines http://images.google.com/imgres?imgurl=www.nyhallsci.org/whataboutaids/whatis/immune/assets/29.jpg&imgrefurl=http://www.nyhallsci.org/whataboutaids/whatis/immune/content.html&h=295&w=390&prev=/images%3Fq%3DHelper%2BT%2BCells%26svnum%3D10%26hl%3Den%26lr%3D%26ie%3DUTF-8%26oe%3DUTF-8

11. T helper cells release cytokines • Special signaling proteins • Stimulate cells • Macrophages • B Cells • Other T cells • Tells Macrophages to double in size and strength • Tells B and other T cells to proliferate http://www.cat.cc.md.us/courses/bio141/lecguide/unit1/bacpath/images/target.gif

12. 2nd type: Killer T cells • CD8+ cell • Has CD8 proteins on them • Cytotoxic T cells=Killer T cells • Activated by cytokines from helper T cells • Start proliferating • Recognize antigens presented by MHC class I • All cells in body have class I MHC • Recognizes cells in body that are infected with viruses

13. Killer T Cells: • Sees cell infected with virus • Kills the cell to stop virus spreading • A cell infected with polio virus can release 100,000 new viruses • Kill it before it finishes making viruses • Killer T-cell punches hole in cell membrane • Host cell lyses open(breaks open) and dies http://www.cancerresearch.org/images/immres6.gif

14. B lymphocytes Antibody-Mediated Immunity Produces antibodies 1. Plasma Cells Produce antibodies 2. Memory Cells Lifelong protection T lymphocytes Cell-Mediated Immunity 1. Helper T cells Help other lymphocytes 2. Killer T cells Kill infected virus Overview