Immunology 146:474

1
Immunology 146474

• Tu, Fri 1st period (840-1000 AM)
• Serc 118
• Dr. Lori Covey-Office hrs 9-1030 Thursday
• Dept. of Cell Biology Neuroscience
• Nelson Hall, B314
• covey_at_biology.rutgers.edu
• Class web site http//lifesci.rutgers.edu/covey/
  Immuno/index.htm

2
Resting T or B lymphocyte
3
Figure 1-6
4
Maturation of the immune response

• Lymphoid organs are separated into primary and
  secondary organs
• Primary--gt bone marrow, thymus
• Secondary or peripheral--gt lymphnodes, spleen,
  mucosal lymphoid tissues (GALT, MALT), provide
  sites for mature lymphocytes to interact with
  antigen

5
Figure 1-7
Ti
Different organs of the immune system
6
The role of bone marrow in immune maturation

• Microenvironment for differentiation of stem
  cells
• Site of origin of B and T lymphocytes, all other
  cells of the immune response
• Antigen-independent maturation of B cells.
• Site for mature re-circulating lymphocyte
  populations

7
Bone Marrow

• Cells move out of Bone Marrow into blood
• The bursa in the bird plays the same role for B
  cell maturation appendix in rabbit

8
The thymus is the site of T cell differentiation

• Primary immune tissue
• Located in the thorax
• Sequestered from antigen
• Two lobes, surrounded by a thin capsule of
  connective epithelium
• Involutes with Age- maximal size at puberty and
  then atrophies

9
Thymus-structure/function

• Thymic stroma--gt network of epithelia-contains T
  cell precursors.
• Dendritic cells, macrophage and medullary
  epithelial cells in thymic medulla
• Sub-capsular epithelium underlying capsule-acts
  as barrier

tr
cortex
m
HC
10
Lymphatic System

• Blood circulates under pressure, fluid component
  (plasma) seeps through capillaries into
  surrounding tissues
• Called interstitial fluid
• An adult-3 liters or more per day
• Returned to blood through walls of the venules
  (prevents edema)
• Remainder of fluid enter lymphatic system

11
Lymphatic System

• Porous architecture of lymphatic vessels (allows
  fluids and cells to enter)
• Thoracic duct largest lymphatic vessel
• Empties into L. subclavian vein (lymph from all
  the body except r. arm and r. side of head)
• Ensures steady-state levels of fluid within the
  circulatory system

12
Lymphatic System

• Heart does not pump lymph
• Lymph flow is achieved by movements of the bodys
  muscles
• Series of one-way valves produces one-way
  movement through vessels
• Foreign antigen is picked up by the lymphatic
  system and carried to lymph nodes

13
Circulation of lymphocytes in response to
infection
14
Peripheral or Secondary lymphoid tissues

• Trap antigen-bearing dendritic cells
• Initiation of adaptive immune response
• Provide signals that sustain recirculating
  lymphocytes

15
Lymph Nodes

• Sites of Immune responses
• Encapsulated bean-shaped structures, reticular
  network, full of lymphocytes, macrophages, and
  dendritic cells.
• First organized lymphoid structure to encounter
  antigens-reticular structures trap antigen
• Morphologically divided
• Cortex
• Paracortex
• medulla

16
Lymph Nodes

• Cortex
• Contains mostly B cells, macrophages and
  follicular dendritic cells
• Paracortex
• Primarily T lymphocytes, and dendritic cells
• Medulla
• Sparsely populated with lymphoid lineage cells
  (mostly plasma cells)

17
Figure 1-8 part 1 of 2
Structure/function of the Lymph Node
18
Structure/function of the Lymph Node
Germinal center foci Reach maximum Size within 4
to 6 days of antigen challenge.
capsule
Med. sinus
Paracortical
GC
19
(No Transcript)
20
Spleen

• Major role in mounting immune responses to
  antigens in the bloodstream
• Filters blood and traps antigens
• Not supplied with lymphatic vesicles
• Splenic artery carries antigens and lymphocytes

21
Structure of the Spleen

• Surrounded by a capsule from which a number of
  trabeculae extend into interior
  (compartmentalized structure)

22
Structure of the Spleen

• Spenic red pulp consists of a network of
  sinusoids
• Populated by macrophages, RBCs, and a few
  lymphocytes
• Site where old and defective RBCs are destroyed
  and removed
• Macrophage engulf RBCs

23
Structure of the Spleen

• Spenic white pulp surrounds the branches of the
  splenic artery
• Forms periarteriolar lymphoid sheath (PALS),
  populated primarily by T cells.
• Primary lymphoid follicles are attached to the
  PALS, are rich in B cells and some contain
  germinal centers
• Marginal zone, peripheral to the PALS, is
  populated by lymphocytes and macrophages

24
Organization of the White Pulp in the Spleen
25
Organization of a germinal center in the spleen

• PFZ-perifollicular zone
• PALS-periarticular lymphoid sheath
• Co-follicular B-cell corona
• MZ-marginal zone
• RP-red pulp

26
Loss of spleen (splenectomy)

• Severity depends on age
• In children, splenectomy often leads to increased
  incidence of bacterial sepsis
• Few adverse effects in adults, can lead to some
  increase in blood-borne bacterial infections
  (bacteremia)

27
MALT or Mucosa-assoc. Lymphoid Tissue

• Mucous membranes lining digestive, respiratory
  and urogenital system are the major sites of
  entry for most pathogens.
• BALT -Bronchus-associated (respiratory)
• GALT-gut-associated (digestive tract)

28
MALT

• Have different organizations.
• Peyers patches in intestinal lining well
  organized
• Barely organized clusters of lymphoid cells in
  lamina propria of intestinal villi
• Tonsils
• appendix
• Large nos. of plasma cells (more than in the
  spleen and lymph Nodes)

29
Figure 1-10 part 1 of 2
30
epithelium
Gut lumin
dome
T-cell area
GC
follicle
31
Antigen transport carried out by specialized
cells called M Cells. Flattened epithelial cells
lacking microvilli M cells have deep invagination
which is filled with B, T cells And Macrophage.
dome
GC
follicle
32
M Cells. Have a deep invagination or pocket, in
the basolateral plasma membrane, which is filled
with a cluster of B cells, T cells
and Macrophage. Antigens in intestinal lumen are
endocytosed into vesicles and Transported from
the luminal membrane to underlying
pocket Membrane Vesicles fuse with the pocket
membrane, delivering antigens To lymphocytes and
macrophage
33
Epithelial surfaces-largest barrier to infection
Skin Epithelial surfaces of the
Gastronintestinal tract Urogenital
tract Respiratory tract
34
Cutaneous-Associated Lymphoid Tissues.
Skin-anatomic barrier to the external
environment. Surface-kertinocytes-secrete
cytokines that set up local inflam- Matory
reactions Langerhans cells-type of Dendritic
cell-antigens are phago- cytosed Migrate from
skin to lymphnodes Intraepidermal
lymphocytes-mostly T cells Dermal layer also
contains scattered T cells and macrophage
35
Different phases of an immune response
innate
36
Pathogens enter the body through mucosal and
epithelial tissue
37
Figure 2-2 part 2 of 2
38
Fixed Defenses of the immune response

• Internal epithelia mucosal membranes
• Secrete mucins-prevent adherence of
  microorganisms.
• Mucus flow driven by beating of epithelial cilia

• Tears and saliva contain lysozyme and histatins
• pH of the stomach and digestive enzymes
• Alpha and beta-defensins-antimicrobial peptides

39
Distinction between pathogens that replicate in
spaces between human cells and within cells

• Extracellular forms of pathogens
• Accessible to soluble molecules of the immune
  system
• Intracellular pathogens attacked by killing
  infected cells
• Both types can be attacked by antibodies at some
  point

40
Receptors involved in the adaptive immune response

• Immunoglobulin receptor (B cell receptor) or
  antibody molecule
• T cell receptor (TCR)
• CD4 and CD8 co-receptors
• MHC class I and class II receptors

41
Blood can be separated in a centrifuge into a
fluid and a cellular fraction. The fluid
fraction is the plasma and the Cellular fraction
contains red blood cells, leukocytes, and
platelets. Plasma contains all of the soluble
small molecules and macromolecules of blood. If
the blood or plasma is allowed to clot, the fluid
phase that remains is called serum. Antibodies
reside in the serum, separated by
electrophoresis--gtsaw four distinct
peaks Albumin, alpha (?) globulin, beta (?)
globulin and gamma (?) globulin
42
Figure 1-16
Structure of an antibody molecule two distinct
parts-Antigen recognition and effector function.
MATURE, naïve or resting B CELL
43
Structure of an Ab molecule
44
Structure of Ab molecules, contd

• Each Ab molecule is composed of 4 polypeptide
  chains
• 2 identical heavy chains and two identical light
  chains
• L chains are linked to H chains and H chains to
  each other via disulfide bonds

45
Structure of Ab molecules, contd

• Light chains are either of lambda (?) type of
  kappa (?) type. Encoded at different loci in the
  DNA
• Light chain polypeptide is designated
• VLCL

46
Ig heavy chains

• IgG most abundant- in humans have 4 IgG
  subclasses- IgG1, IgG2, IgG3 and IgG4
• Confer effector function of the molecule

47
Structure of the Ab molecule
Protease papain cleaves Ab--gt2(Fab) and Fc
region Fab fragment antigen binding, Fc
Fragment chrystallization
48
Structure of the Ab molecule
Protease pepsin cleaves Ab molecule into F(ab)2
pFc
49
Classes or Isotypes of immunoglobulins

• Antibody (Ab) immunoglobulin (Ig)
• Each B cell expresses a unique Ig
• The C part of the antibody molecule is
  conserved among classes of antibodies

50
Antibody Isotypes, contd

• An isotype refers to the class of heavy chain
  polypeptides
• isotypes, IgM, IgD, IgG, IgA and IgE.
• Heavy chain polypeptide is designated
• VHCH
• Mature, naïve or resting B cells express only IgM
  and IgD on their surfaces

51
Pure immunoglobulin obtained from multiple
myeloma patients made sequencing protein
possible Multiple myeloma is a cancer of
antibody-producing plasma cells Highly
proliferative, divide in a non-regulated way
without requiring stimulation with antigen Cell
secretes molecularly homogeneous
antibody Produce excess of light chains called
Bence-Jones proteins because they are
homogeneous can be sequenced
52

• Light Chains--gt amino terminal half of the chain
  were found to be variable (called V region),
• carboxy terminal was more constant (C region)
  with only two types ? and ?

53
Structure of an antibody molecule
54
Protein chemistry
Hinge region
Proteins are made up of 20 amino acids, structure
is determined by the aa side chains
55
(No Transcript)
56
Protein Chemistry
Different types of bonds formed by interactions
between amino acids
57
Protein Chemistry

• Primary structure of a protein--gt amino acid
  sequence
• Secondary structure--gtlocal interaction between
  amino acids

M
T
P
V
C
Y
?-helix
58
Protein Chemistry
Secondary structure--gt anti-parallel ? strands
59
Protein Chemistry

• Tertiary structure--gtpacking of structural
  elements into one or several compact globular
  units called domain

60
Protein Chemistry

• Quartenary--gtmultiple polypeptide chains form the
  active molecule

61
Figure 3-5 part 2 of 2
Ig light chain polypeptide, N-terminus is the
variable (V) region and C-terminus is the
constant (C) region 2 beta sheets in either the
C or V domain held together by disulfide bonds
62
Domains of an Ig molecule are similar
Similar folded Structure called Ig fold
63
Immunoglobulin Fold

• 2 beta pleated sheets-
• Beta pleated sheets consist of at least two ?
  strands running in opposite directions
  (anti-parallel)
• Linked by disulfide bonds
• Form a structure called a ? barrel

64
Ab Structure
VL
CH1
CL
Hinge region
VH
CH2
CH2
CH3
CH3
65
Within V regions--gt 3 regions of elevated
variability
66
HV region called Complementary Determining Regions
or CDRs CDRs contact antigen
67
Ab Structure
Hinge region
68
Ab recognition of antigen

• Juxtaposition of the CDRs of both heavy and light
  chains form a pocket that recognizes antigen.

69
Haptens

• Small molecules that can be recognized by Ab but
  cannot stimulate the production of anti-hapten
  antibodies unless linked to a larger carrier
  protein such as BSA.

70
Haptens

• Small molecules that can be recognized by Ab but
  cannot stimulate the production of anti-hapten
  antibodies unless linked to a larger carrier
  protein such as BSA.

Ab formed
Immunize rabbit
none
Dinitrophenol (DNP) hapten
Anti-BSA
BSA carrier
Anti-DNP
Anti-BSA
Anti-DNP/BSA
71
Haptens

• Demonstrates the broad range of epitopes that can
  be recognized by an antibody. Also, the
  hapten-carrier system is a tool to probe the
  effects of minor variations in chemical
  structures on immune specificity.

72
Join two hapten molecules together can observe
flexibility of Ab molecule
73
Different types of epitopes on antigens
recognized by antibodies

• Linear epitopes (recognition sites on antigens)
• Conformational or discontinuous epitopes

74
Surfaces created by different amino acids in the
CDRs are distinct
Hapten-Ab conjugate
Peptide-Ab conjugate
75
Surfaces created by different amino acids in the
CDRs are distinct
Hen-egg lysozyme
Gp120-Ab Complex