immunology
TRANSCRIPT
1. Complement
System2. Phagocytes (neutrophils,
macrophages, mast cells)
INNATE IMMUNE SYSTEM
ADAPTIVE IMMUNE SYSTEM
Lymphocytes: T and B Cells
cells of innate immunity
Cells of adaptive
immunity.
Lymphocytes are usually defined by where they
undergo their “ basic training” ---
Thymus- derived. Bone marrow derived.
T – lymphocytes/ T cells B – lymphocytes/ B
cells
Natural killer T/ NKT cells.
Lymphocytes can also be defined by the type of
receptor they display on their cell surfaces
TCR BCR / Ig neither
- T cells - B cells - Natural killer
cells
- NKT cells
The T cell can be identified by the presence of the
CD-3(cluster of differentiation ) molecule which is
associated with TCR on the T cell surface.
Two other CD molecules are used to identify CD3+
T cell subsets , CD 4 + and CD 8 +
CD 4 + T CELLS
It accounts for approx. 2/3rd of mature CD3 + cells.
Also known as Helper T ( Th) cells.
CD 4 molecules displayed on the surface of these
cells recognize a non peptide binding portion of
MHC class II molecules, thus are restricted to the
recognition of
p MHC class II complexes.
T helper 1(TH1)- regulation of cellular immunity.
-Interferon – y, IL- 2.
T helper 2 (TH 2)- helps B cell in isotype switching.
- Production of antibodies.
- IL- 4, IL-5,IL-6,IL-10.
Interferon – y inhibits TH 2.
IL-4 & IL-10 inhibits TH 1.
CD 8 + T cells
Comprises approx. 1/3rd of all mature CD3 + T
cells.
These are ‘restricted’ to the recognition of p MHC I
complexes.
Also known as –
A) Cytotoxic T ( Tc) – identification of cells infected
with
intracellular organisms, viruses
and
bacteria and eliminate such
cells.
B) Suppressor T ( Ts ) – Down regulation of immune
response.
NATURAL KILLER CELLS
Large lymphocytes ( 5 – 10% of peripheral blood
lymphocytes ) which develop in the bone marrow.
They have an ability to kill virally infected cells and
tumor cells without prior sensitization ( no need for
antigen recognition)
Receptors - KARs and KIRs
THYMOCYTE DEVELOPMENT: +VE/-VE
SELECTION
T CELL ACTIVATION
CD 4+ T cell
APC = e.g., Macrophage
CD4MHC
Class II
Peptide
Antigen
TCR
1st signal.
Formation of
pMHC: TCR: CD
2ND signal.
Costimulatory
Molecules.
+
1
2
CD 4 + CELL MATURATION.
TH 1
TH 2
CD 8 + T CELL MATURATION
p MHC CLASS I: TCR: CD8 +( 1st signal)
expression of IL – 2 receptors
IL – 2 secretion by primed CD4+
( 2nd signal)
cytotoxic T Lymphocytes
cell lysis