Lymphoid Functional Anatomy

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Lymphoid Functional Anatomy

• The role of secondary lymphoid organs in trapping
  antigens
• For Tuesday Week 6 Practical Workshop, Dunnbook
  Chapter 10
• Comments and Feedback please to the Author,
  simon.hunt_at_path.ox.ac.uk

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Purposes of this presentation

• To show how the siting of lymph nodes in the
  body, interconnected by lymphatic vessels, serves
  to trap pathogens at the local draining nodes
• Examples are of material
• inoculated through the skin plague
• injected to a muscle an antigenic adjuvant
• inhaled to the lungs anthrax
• To encourage you to explore areas you find
  interesting by following hyperlinks
• To encourage you to keep your eyes open for
  features of interest and for the physical
  dimensions, especially of images

Presentation objectives
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Lymphatics and Lymphoid organs, overview
The lymphatics shown here are the superficial
ones draining the skin. If all the lymphatics
that drain organs were also shown, she would be
green all over. Check that you know the
difference between lymphatic and lymphoid.
? Why is it important to know the routes of
lymphatics in cancer patients?
From http//www.newhopehealthclinic.com/symptoms_l
ymphoma_lymph_glands_swollen.htm
Here is a more detailed view in a child. Note
the chains of nodes
Lymphatics and Lymphoid organs, overview
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Lymph Node Chains in Three Body Regions
Try palpating an accessible node see
http//home.teleport.com/bobh/Nodes.htm )
especially if you or your practical partner has
an infection which has caused one to swell
From http//www.jdaross.mcmail.com/lymphatics4.htm
Lymph20nodes
Lymph node chains in three regions
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Surface Locations of Lymph Node Chainsin Head
and Neck
Heres a chance to revise your knowledge of ?
Anterior, Posterior, Pre-, Supra-, Sub-.
? Write a description of the immediate
surroundings of the lymph node. The material in
which it is embedded here is very typical.

• A typical active lymph node, e.g. in an infection

Surface Locations of Lymph Node Chains
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Cancer enlarged Lymph Node with lymphoma
Its pretty important for clinicians to get it
right between lymph node enlargement due to an
immune response, and to a tumour. Thats part of
clinical training, but you could start thinking
now how a scientific approach could assist in
making the distinction
Pathologists are fond of food metaphors for the
very inedible specimens they study. Can you
think of other examples?
Compare scale with previous slide
Cut sections of this enlarged lymph node involved
with high-grade non-Hodgkin's lymphoma in AIDS
reveal a "strawberry sundae" appearance with
swirls and globs of red in white. From
http//medlib.med.utah.edu/WebPath/TUTORIAL/AIDS/A
IDS088.html
An enlarged lymphomatous lymph node
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Abdominal lymphangiogram
? Sketch a stick-man schematic to make it clear
from which view this X-ray was taken

• This illustrates the connections between chains
  of lymph nodes by lymphatics

From http//www.med.umich.edu/lrc/coursepages/M1/a
natomy/html/radiology/xray/lymphangiogram.html
? What might be the likely biological purpose of
arranging lymph nodes in a series of chains like
this?
? Anything odd in this image?
Lymphangiogram
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Plague
If the history and current status of plague
epidemiology interest you, see the recent WHO
report
Fleas transfer the bacterial infection (Yersinia
Pestis) from rodents by subcutaneous inoculation
to various animals and to people. Initial signs
and symptoms may be nonspecific with fever,
chills, malaise, myalgia (muscular pain or
tenderness), nausea, prostration, sore throat and
headache. Commonly a lymphadenitis (inflammation
of the nodes) develops in those lymph nodes that
drain the site of the flea bite, where there may
be an initial lesion. This is bubonic plague, and
it occurs more often in lymph nodes in the
inguinal area and less commonly in the axillary
and cervical areas. The involved nodes (buboes)
become swollen, inflamed and tender and may
suppurate (i.e. form or discharge pus). Once it
has spilled into the bloodstream, the infection
is systemic. From http//www.ph.ucla.edu/epi/bio
ter/plagueapha_id_a.html
Plague
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Antigen transport by dendritic cells following
intramuscular inoculation
The cells that have taken up the antigen are
dendritic cells, shown in green in this
higher-power view
Within the inguinal (draining) node the antigen
is quite deep below the surface the arrows mark
the border. More on this next class
In the first couple of hours the antigen is not
yet cell associated, but after two days most of
it is internalised
Note the scale bar!
? What is an adjuvant?
Data from Dupuis et al, Dendritic Cells
Internalize Vaccine Adjuvant after Intramuscular
Injection Cellular Immunology 186 18 (1998)
Antigen fate after i.m. injection
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Inhaled Antigens the Lung
Knowledge of functional lung anatomy is essential
for clinicians to deal with infections that
overwhelm the normal non-specifc immune defences
which keep the alveoli normally sterile. ?Write
a checklist of these defences.

• Pulmonary Lymphoid System comprises
• Lymphatics- Originate in the pleura- Have
  valves- Drain towards hilum- Follow
  interlobular septa- Accompany blood vessels
• Draining lymph nodes (shown yellow)
• intrapulmonary
• mediastinal

The bacterial disease anthrax is in the news as
an inhaled pathogen. It is a toxigenic bacillus
whose details you are not required to know.
However, the next two pages make the point that
the radiology of the lymph nodes can often give
the quickest diagnosis, and reveal the role of
the lymphoid organs when non-specific defences
have been breached
Pulmonary lymphoid system 1
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Anthrax in a postal worker, USA 2001
With a lymphatic vessel filled like that, it
isnt surprising the outcome sadly was fatal
Anthrax
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Pulmonary lymphoid system in anthrax
CT imaging demonstrates bulky high-attenuation
hilar and mediastinal lymphadenopathy which may
produce bronchial and vascular narrowing. Large
rapidly-progressive pleural effusions are
characteristic. The portal of entry is the airway
and the organisms are rapidly transmitted via the
lymphatics to the intrathoracic lymph nodes and
ultimately to the blood stream. Despite the
inhalational acquisition of the disease, the lung
parenchyma remains relatively uninvolved. From
http//anthrax.radpath.org/Summary2.html
Pulmonary lymphoid system 2
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Pathologies of lymph nodes

• If you have some time to spare you may like to
  visit http//home.teleport.com/bobh/CommonPathofL
  ymphNodes.htm which shows diseases involving
  lymph nodes of the head and neck, including
• Infectious Mononucleosis (Glandular fever)
• Non-Hodgkin's Lymphoma
• Persistent Generalized Lymphadenopathy
• Cat Scratch Disease
• Metastatic Carcinoma

You have probably by now mastered the meaning of
lymphadenopathy since that has appeared a
number of times, but ? what about
lymphadenectomy?
Pathologies of lymph noders
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Summary

• Pathogens at first encounter innate immune
  defences, e.g.
• Skin epithelial barriers
• Airway filtration and epithelial secretions
• Phagocytosis, perhaps aided by opsonisation by
  Complement
• If the defences are overwhelmed or bypassed, the
  pathogens travel via afferent lymph
• in fluid phase or cell-associated
• to draining lymph nodes
• usually a chain of nodes are arranged in series
• The adaptive immune response starts in the
  draining node