Lymphoid System Flashcards
What are the two major types of lymphocytes and their associated immunological responses?
T-Lymphocytes- Cell-mediated immunity
B-Lymphocytes- humoral immunity (B-cells differentiate into plasma cells and secrete antibodies)
Lymphocytes are “recirculating, Immunocompetent” cells. What does this mean?
Recirculating- travel through blood/lymphatic vessels and lymphoid tissue.
Immunocompetent- Ability to recognize a single foreign antigen
Recirculation ensures that the “correct” immunocompetent lymphocytes will detect an antigen, regardless of location of infection.
What’s the difference in Primary and secondary lymphoid tissue?
Primary- lymphocytes differentiate into T&B cells
Secondary- Foreign antigens are captured/controlled here. (Positioned near common sites of foreign antigen presence)
Where do T-cells mature?
Thymus
Where do B-cells mature?
Bone Marrow
Areas of loose connective tissue where large members of lymphocytes and plasma cells are present are called?
Diffuse Lymphatic Tissue
What are some common locations of diffuse lymphatic tissue?
Digestive, Respiratory, Urogenital tracts
If a foreign antigen gets past the epithelium of the digestive system, where will lymphocytes intercept it?
Lamina Propria immediately deep to the epithelium
A discrete concentration of lymphocytes contained in a meshwork of reticular cells is called?
An Isolated lymphatic nodule/follice
Where are isolated lymphatic nodules generally located?
Digestive, Respiratory, Urogenital tracts
What are the 2 types of isolated lymphatic nodules?
Primary lymphatic nodule- oval accumulations of small lymphocytes beneath the epithelium.
Secondary lymphatic nodule- Lighter central region with large lymphocytes (mostly Bcells) and dark outer region of small lymphocytes
When do secondary lymphatic nodules form?
After antigen exposure - location of immune response (high B-cell concentration = more antibody secretion)
What are PERMANENT aggregates of lymphoid nodules called?
Aggregated lymphoid nodules.
Examples: Peyer’s Patches/Appendix, tonsils,
Where are Peyer’s Patches located?
Ileum, on ONE SIDE of intestinal wall.
What does MALT stand for?
Mucosal Associated Lymphoid Tissue. Constitutes 85% of lymphoid tissue in the body, because mucosa are the most common site of entry for microorganisms.
What permanent aggregated lymphoid structures capture and mount immune responses to antigens entering through the mouth and nose?
Tonsils
Name the 3 kinds of tonsils.
1) Pharyngeal- roof of pharynx
2) Palatine (“the tonsils”) - either side of pharynx
3) Lingual- base of tongue
What type of epithelium lines the tonsils? (think mucosa)
Non-keratinized stratified squamous epithelium
Why do tonsils become infected easily?
Deep crypts- no clear border between epithelium and parenchyma
What is the stroma and parenchyma of a lymphoid organ?
Stroma- supporting framework (generally CT/reticular fibers)
Parenchyma - functional part of an organ
Lymphoid nodules generally contain which 3 types of cells?
B-cells, Plasma Cells, and Macrophages
In lymph nodes, where are B-cells located?
Outer cortex in nodules
In lymph nodes, where are T-cells located?
Paracortex
How do lymphocytes get into the lymph nodes?
Postcapillary venules inside lymph node are lined with HIGH CUBOIDAL CELLS which have surface receptors that specifically recognize lymphocytes.
These venules are more specifically called HEVs (high endothelial venules)
