blue/black cells are Von Kuppfer’s cells (macrophages of the liver) – liver cells form plates that are
separated by spaces- space of Diess, drainage that opens to lymphatic system, tissue specific
macrophages are here
Von Kuppfer’s cells
space of Disse
von Kuppfer’s Cell
Space of Disse
Recall some of these are antigen presenting- can initiate an immune response early on
Trachea (cartilaginous rings evident)
esophagus
Tracheal epithelium
lymphocytes (not encapsulated so not a nodule)
lamina propria
MALT= mucoid associated lymphoid tissue
Lymphocytes are identifiable by very large nucleus- very densely packed, thin surrounding cytoplasm,
cell is not associated w/ underlying tissue (usually found in the CT underlying the epithelium)
Mammary Glands
Glands
plasma cell
surrounding CT
Glands are full of plasma cells that secrete IgA- main source of a neonatal immune system
Plasma cell nuclei have DISTINCTIVE wheel spoke nucleus- Plasma cells have an oval shape with an
eccentrically located nucleus. The chromatin of the nucleus is arranged in a pattern similar to the spokes
of a wagon wheel with a central nucleolus. The cytoplasm is rich in ribosomes and proteins, which
usually produce a dark uniform purple stain
Plasma cells are activated forms of B cells- create antibodies specific for the antigen that activated them
Peyer’s Patches
epithelium
lumen
smooth muscle
CT of the LP
Peyer’s patches are unilateral in the GI tract- opposite the side of the mesentery
Note the patches are located deep to the epithelium w/in the lamina propria (LP is obscured by the
density of the patches)
All pictured are activated as evidenced by the lighter core (B cells that have undergone blast
transformation)- fewer cells filling a larger space
Recall patches have a T cell domain and a B cell domain
T cell domain faces epithelium of the luminal border (region where M cells are- not distinguished in this
stain)
T Cell cap
Germinal Center- B cell region under active division
Epithelium
lumen of the SI
Palatine Tonsils
Stratified squamous mucousal epithelium
crypts
stimulated follicles
non-stimulated
B cells from the activated follicles form plasma cells that travel to the lymph vessels of the crypts then
into the adjacent lymph nodes where they mature. Once mature the plasma cells return (homing) to
the tonsil and are active against the antigen that activated them.
Smooth muscle glands palatine tonsil tissue
Pharyngeal tonsil tissue
Seromucus glands
Seromucus glands are diagnostic of pharyngeal tonsil tissue as opposed to palatine tonsil tissue which
have purely mucus glands
Other key diagnostic feature is PCCE (respiratory epithelium) instead of the squamous epithelium of the
palatine tonsil
Follicles and are other structures are equivalent
Lymph nodes:
Cortex
Medullary sinus
paracortex
medulla
secondary nodule
primary nodule
medullary cord (cellular islands)
Medullary sinuses are lined with macrophages, B cells, T cells and serve as major sites of immune
function on the lymph fluid
Medullary sinus
medullary cord
germinal centers
paracortex
trabecula
T cell domain = paracortex in a lymph node (region between germinal centers and the medulla)
Medulla – region for collection of lymph fluid, filtration, and return to body
2 functions of lymph nodes- cleaning of lymph, immunological surveillance
Lymphocytes enter the cortex through high endothelial venules (difficult to find on posted board)
Correct lymph flow path:
vein (in the hilus)
Lymph Vessel
subcapsular sinus to trabecular sinus to medullary sinus to lymphatic
lymph vessel valve
Issues with edema, varicose veins, DVT, etc. have direct effect on lymph clearance
Lymph vessels are driven exclusively by skeletal muscle pump action- valve is composed of endothelium
w/ a very thin layer of CT between 2 layers- valves are necessary to prevent backflow in this system
Splee
An encapsulated structure w/ trabecula
Capsule
red pulp
white pulp
T cell domain- form a sheath around the central arteries of the white pulp- periarteriolar sheath (PALS)
Red pulp
white pulp
central arteriole
PALS
marginal sinus (contains B cells)
These vessels are branches of the splenic artery and vein that enter and leave
(respectively) the spleen through the hilum. The rest of the organ is taken up by splenic
pulp which can be classified as either red or white pulp. White pulp consists of masses of
lymphatic tissue, which in stained tissue sections appear as round masses of darkly
staining lymphocytes. Germinal centers may or may not be present. The white pulp
contains an artery, the central artery. At low magnification, the central artery in cross
section appears as a small round, red staining mass in the white pulp. This is diagnostic
for the spleen. When the central artery originates from the trabecular artery and leaves the
trabecula, it is immediately surrounded by lymphoid tissue (white pulp). This lymphoid
tissue is called PALS, periarterial lymphoid sheath. Look for radial branches of the
central arteries. Identify the marginal zone region at the periphery of the white pulp. This
region is a shell of large but ill-defined vascular tissue called the marginal zone, in which
most of the white pulp capillaries are found. This zone is extremely variable in size and
content and is completely devoid of sinusoids. In this section, the marginal zone is looser
in texture than the white pulp and contains blood cells, lymphocytes, macrophages and
reticular cells.
The red pulp makes up the bulk of the splenic pulp and is the remaining lighter (red)
staining tissue surrounding the white pulp. It contains large numbers of RBCs as well as
lymphocytes. Look for the splenic sinuses and splenic cords (Billroth’s cords). At high
magnification, the splenic sinuses are endothelial lined spaces. They may be difficult to
visualize. They may be packed with RBCs or completely empty. Look for a cross section
of a red pulp sinus where the gaps between the endothelial cells are visible.
sinusoid- lined by endothelial cells & macrophages (large dark cells = macrophages)
Macrophages phagocytose old/damaged RBCs from the sinusoids
Thymus- bilobate structure
Individual lobules
cortex medulla
T cells all mature in the cortex
Hassell’s Corpuscles – DIAGNOSTIC, derived from type 6 tissue- These are red staining spheres of
concentrically layered cells found in the medulla. The lymphocytes in the medulla are not as densely
packed as those in the cortex. T-lymphocytes proliferate in the periphery of the cortex and then migrate
towards the medulla
Cortex medulla
blood vessel
CT of trabecula
hassell’s corpuscles