Immune Histology Flashcards
(24 cards)
Diffuse lymphatic tissue
Somewhat disorganized
Occurs within other tissue types
Nodular lymphatic tissue
Very dense aggregations of lymphoid cells
Often called lymphatic nodules/follicles
Primary lymphatic organs
Thymus and bone marrow
Where immune cells undergo antigen-independent proliferation and differentiation into cells pre-programmed to recognize specific antigens
Secondary lymphatic organs/tissues
Effector lymphatic tissue
Lymph nodes, tonsils, spleen
Masses of lymphatic tissue surrounded by CT capsule
Include diffuse tissue and nodules
Lymphocytes undergo antigen-dependent proliferation and differentiation into effector lymphocytes and memory cells
When does the thymus begin to be replaced by adipose
Puberty
Trabeculae
Parts of the CT capsule around the thymus that divide it into lobules
What is found in the capsule and trabeculae of the thymus?
Blood vessels Efferent lymphatic vessels Nerves Fibroblasts Variety of immune cells Adipose cells
Epithelioreticular cells
Provide the supporting framework of the thymus
Cortex of thymus
Dark staining region (contains densely packed, small, immature T cells)
Small population of epithelioreticular cells and phagocytic macrophages
Where are the macrophages found in the thymus?
The corticomedullary junction
They phagocytose any t cells that do not fulfill thymic education requirements
Medulla of thymus
Contains more mature T cells
Also contains epithelioreticular cells and DCs
T cells are less numerous, larger, and paler staining
Hassall’s corpuscles
Found in the medulla of the thymus
Specific type of epithelioreticular cell
Believed to be involved in the removal of dead T cells
3 major elements of the blood-thymus barrier
- Capillary endothelium
- Perivascular connective tissue space with macrophages
- Epithelioreticular cells (thymic nurse cells)
Parts of a lymph node
Cortex (superficial cortex and paracortex)
Medulla (cords and sinuses)
Capsule
Trabeculae
Flow of lymph through a lymph node
Enters through afferent lymphatic vessels
Drains into subcapsular sinus
Filtered through trabecular sinuses
Flows into the medullary sinuses
Conveyed away from node via efferent lymphatic vessels at the hilum
Superficial cortex of lymph nodes
Organized into nodules
Primary if they have unstimulated B cells
Secondary if they have stimulated B cells
Secondary nodules have germinal centers
Germinal centers
Lighter in appearance because stimulated B cells are larger, have more cytoplasm, and stain lighter
Paracortex of lymph nodes
Contains most of the T lymphocytes
Medulla of lymph nodes
Consists of medullar cords and sinuses
These contain reticular cells and lymphocytes
Also macrophages, DCs, and plasma cells
Reticular meshwork
Support of lymph node
Composed of stellate reticular cells and their reticular fibers
Palatine tonsils
Incompletely encapsulated masses of nodular lymphatic tissue at the base of the oropharynx
Lined by stratified squamous non-keratinized epithelium
Forms tonsillar crypts
CT contains many lymphatic nodules
Functions of spleen
Phagocytosis of old RBCs
Recycling of iron
Capture and destruction of blood borne pathogens
Induction of the adaptive immune responses
Houses 1/4 of body’s lymphocytes, stores 1/3 of platelets
Red pulp
Consists of splenic cords and sinuses
Blood leaves capillaries, flows through cords, and collected by sinuses
Old RBCs get trapped in the cords and cleared by macrophages (also recycle the iron)
White pulp
Sheaths of lymphoid cells
T and B cell compartments surrounding the branching arterial vessels
Allows for the detection and destruction of blood-borne pathogens
