Louisiana Cuisine

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Louisiana Cuisine

• We eat anything that
• Jumps
• Runs
• Burrows
• Crawls
• Flies
• Swims

frogs
river rat (nutria?)
crawfish, oysters
alligator
all kinds of birds
fish, shrimp, turtle, crab
In other words, we love Fast Food!
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Lymphocytes and the Immune SystemFriday,
October 3, 2003

• Reading-
• Anatomy and Physiology- Lymphocytes and Spleen
  (pp 8-11)

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Lymphocytes and the Immune SystemFriday,
September 27, 2002

• Reading-
• Anatomy and Physiology- Lymphocytes and Spleen
  (pp 8-11)

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Lymphocytes Maturation Pathways of B-, T- and
Natural Killer (NK) cells
Smallest and second most common group of
leukocytes in the bloodstream.   Recognized by
their round/oval nuclei with little cytoplasm.
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Lymphopoiesis
Occurs in two distinct phases   It all starts
when the lymphoid stem cell differentiates to
form antigen-committed lymphocytes   This
process occurs in the primary lymphoid
organs   --T-lymphocyte differentiation occurs
in the thymus,   --B-lymphocyte differentiation
takes place in the fetal liver and adult bone
marrow.
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Lymphopoiesis (contd)
Antigen-dependent proliferation and development
of T- and B-lymphocytes occurs in the secondary
lymphoid organs --spleen --lymph nodes
and --mucosa-associated lymphoid tissues (which
include tissue in the trachea, tonsils, Peyer's
patches and the appendix).
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B-Lymphocyte Development
First step in differentiation of B-lymphocyte
stem cell line is the rearrangement of the
immunoglobulin heavy chain genes. Successful
rearrangement permits synthesis of IgM chains in
the cytoplasm of the cell   --cytoplasmic m
chains key features of pre-B lymphocyte.
Rearrangement of the immunoglobulin light
chain genes results in the expression of IgM on
the cell surface, and this cell is termed the
immature (or virgin) B-cell. The next cell to
evolve is the activated/stimulated (adult)
B-cell.
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B-Lymphocyte Development (contd)
These activated B-cells can produce all kinds of
secreted immunoglobulins. For a B cell to reach
this stage of development, it must first be
stimulated by foreign antigenic presentation by
an APC. Differentiation continues to mature
plasma cell with extensive endoplasmic reticulum,
numerous ribosomes, and an active Golgi
apparatus-- signs of an actively secreting
cell! The plasma cell will actively synthesize
and secrete monoclonal antibody of the
specificity of the inducing antigen.  Some
plasma cells revert to the quiescent state, but
can mount a rapid response following further
contact with the inducing antigen memory cells.
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Development of B-Lymphocytes
Surface Ig
Cytoplasmic Ig
Stem cell
Pre-B cell
Virgin B cell
Mature plasma cells
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T-Lymphocyte Development
During fetal development, T-lymphoid stem cells
populate the thymus gland where under the
influence of epithelial nurse cells they
proliferate and divide.   These early lymphoid
precursors (early thymocytes) express a unique
membrane molecule known as Thy-1. These cells
lack other membrane proteins unique to
T-cells. Progeny of these lymphoid stem cells
progress from the thymus and join the circulation
as small T-lymphocytes and go to the peripheral
lymphoid tissues.
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T-Lymphocyte Development (contd)
These small T-lymphocytes now await activation
by an antigen-bearing-APC cell. When activated,
the first step is the development of a large
blast cell commonly known as the
lymphoblast.   This blast undergoes division to
a prolymphocyte.   Once cell division stops,
this cell becomes an immature lymphocyte and it
is released into the bloodstream, which then
matures into a mature active T-cell.
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T-Lymphocyte Development
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T-Lymphocyte Subsets (contd)
CD4 T-lymphocytes (65 of peripheral blood
T-cells are CD4) T-helper lymphocytes (TH) -
help and induce activation of B-lymphocytes and
secrete IL-2, interferon-gamma act as growth
factors T-delayed-type hypersensitivity (TDTH)
- secrete chemotactic factors for macrophages.
CD8 T-lymphocytes (35 of peripheral blood
T-cells are CD8) Suppressor T-lymphocytes (TS)
- act as a brake on TH lymphocytes Cytotoxic
T-lymphocytes (TC) - release cytolytic substances
such as perforin directly onto target cells.
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Natural Killer (NK) Cells
A group of cells classified neither as B- or
T-cells, are considered "null cells". NK cells
are the biggest of this group   --lack receptors
for antigen recognition --cannot participate in
acquired immunity   More closely related to
innate immune response. What makes NK a cell
unique is their spontaneous ability to kill tumor
cells and virus-infected cells, which produce
large quantities of ?-interferon (IFN-?).
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Anatomy of Lymphatic Organs
Thymus   --site of T-lymphocyte
differentiation --most active during fetal life
when it becomes populated with committed lymphoid
stem cells   --task of populating secondary
lymphoid tissue with mature antigen-committed
T-lymphocytes is done in the first months of
life, after which thymic activity diminishes.
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Anatomy of Lymphatic Organs (continued)
Bone Marrow   --in birds, the primary lymphoid
organ responsible for the maturation and
differentiation of B-lymphocytes is the Bursa of
Fabricius.   --in humans, induction of
B-lymphocyte differentiation is one of the many
functions of bone marrow.
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Anatomy of Lymphatic Organs (continued)
Bone Marrow In 1957, Glick and colleagues were
trying to define the function of the Bursa of
Fabricius in chickens --it was known to be
active early in life and the largest in size.
They removed the organ and nothing discernable
happened.   --these adult birds were recruited
to a student exercise to raise antibodies, and
they failed to synthesize an antibody response to
the antigen. --this strange but very
important observation may be one of the most
important one made in defining the role of
B-lymphocytes as a mediator of humoral immunity,
and it was discovered because of a lack of school
resources (for teaching purposes) to buy new
chickens!
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Anatomy of Lymphatic Organs (continued)
Spleen   Largest of the lymphoid organs,
performs a number of functions, including   (1)
blood filtration- selectively removes senescent
or antibody-coated red cells from the
circulation.   (2) blood pooling- 1/3 of the
total platelet mass is here, and it is in dynamic
equilibrium with the circulating pool. About 5
of total red blood cell mass is here.
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Anatomy of Lymphatic Organs (continued)
Spleen Function (continued) (3) immune function-
filtering action collects and concentrates
blood-born foreign antigens for processing by the
immune system. Major site of antibody synthesis
within the body. (4) hematopoietic function-
normally is a hematopoietic organ in utero, can
resume under extreme conditions.
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Anatomy of Lymphatic Organs (continued)
red pulp consists mainly of cords and sinuses,
which are simply vascular spaces lined with
macrophages. All blood cells must move between
these sinuses and macrophages.   the central
arteries are surrounded by white pulp, which is
made up of mainly lymphoid tissue with loosely
packed lymphocytes, containing both B- and
T-lymphocytes.   boundary between white and red
pulp is the marginal zone and is rich in
dendritic APC's that capture, process and present
foreign antigen for T-cell stimulation.
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Anatomy of Lymphatic Organs (continued)
Lymph Nodes   Lymphatic circulatory systems act
as a drainage system for excess interstitial
fluid or lymph.   Many structural similarities
to the blood circulatory system   --smallest
lymphatic vessels are called lymphatic
capillaries and they penetrate deep into almost
all tissues   --lymphatic capillaries drain into
larger vessels equivalent of veins   --largest
vessels, like arteries, are muscular and actively
pump lymph into the thoracic duct.
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Anatomy of Lymphatic Organs (continued)
Lymph nodes are small bean-shaped structures
that are found in clusters at junctions in the
lymphatic circulatory systems.