T Cells:Adaptive/Specific Immunity Immunity Immunity

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

T-Cells Start from hemapoietic stem cells in bone marrow Start from hemapoietic stem cells in bone marrow Travel to thymus to mature Travel to thymus to mature –Thymus: organ above heart DOES NOT secrete antibodies DOES NOT secrete antibodies

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

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

Every Body cell has MHC molecules MHC: Major Histocompatability Complex MHC: Major Histocompatability Complex –Area of genes on chromosome 6 A protein found spanning cell membranes A protein found spanning cell membranes Two types 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

MHC must match for Organ Donation MHC genes complex most polymorphic KNOWN to man MHC genes complex most polymorphic KNOWN to man –Many alleles for same genes –Thousands of different combinations In a study of 1000 individuals 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 Their job is to show all the proteins in the cell

MHC presents peptides ALL proteins in a cell are broken down 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 Peptides are presented on cell surfaces by MHC MHC has a groove like a bun MHC has a groove like a bun –Peptide is hot dog that fits inside

1 st type: T helper Cells 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 MHC II is only found on macrophages and B-Cells –EX. Macrophage eating salmonella bacteria

1 st type: T helper Cells Macrophage ingest bacteria and break down proteins Macrophage ingest bacteria and break down proteins –Present on surface with Class I MHC molecules T-helper cells bind the antigen-MHC complex T-helper cells bind the antigen-MHC complex –Releases cytokines pg&imgrefurl= rev=/images%3Fq%3DHelper%2BT%2BCells%26svnum%3D10%26hl%3Den%26lr%3D%26ie%3DUT F-8%26oe%3DUTF-8

T helper cells release cytokines Special signaling proteins Special signaling proteins Stimulate cells Stimulate cells –Macrophages –B Cells –Other T cells Tells Macrophages to double in size and strength Tells Macrophages to double in size and strength Tells B and other T cells to proliferate Tells B and other T cells to proliferate

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

Killer T Cells: Sees cell infected with virus Sees cell infected with virus Kills the cell to stop virus spreading 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 Killer T-cell punches hole in cell membrane –Host cell lyses open(breaks open) and dies

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