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T Cells:Adaptive/Specific
Immunity
Immunity
Review of B cells
B cells fight antigens by producing
antibodies
 Fights antigens floating around your body

T-Cells

Start from hemapoietic stem
cells in bone marrow

Travel to thymus to mature
– Thymus: organ above heart
http://www.mdausa.org/images/qpix/q44thym3.jpg

DOES NOT secrete antibodies
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
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
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 HLAD
 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
– 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
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
st
1

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
st
1

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.j
pg&imgrefurl=http://www.nyhallsci.org/whataboutaids/whatis/immune/content.html&h=295&w=390&p
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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
nd
2

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
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
Overview

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