1. Tissues of the Immune System Flashcards
Primary lymphoid organs examples
Thymus and bone marrow
Secondary lymphoid organs examples
Spleen, lymph nodes, mucosal associated (MALT, GALT, BALT)
What does the B in B cells indicate?
Cells derived from Bursa (first seen in birds) equivalent tissues (of which includes bone marrow and foetal liver)
What are primary lymphoid tissues?
Involved in development and differentiation of lymphocytes
What are secondary lymphoid tissues?
Where antigens and lymphocytes accumulate and are brought together to bind
What are tertiary lymphoid tissues?
Maybe invaded by unique subsets of memory lymphocytes during inflammation
Tertiary lymphoid organs examples
Skin
What is the structure of the thymus?
Two lobes divided into smaller lobules by trabeculae. Each lobule has an outer cortex and inner medulla. Gets smaller with age
What is thymocyte development affect by?
Thymus nurse cells
What are naive lymphocytes?
Lymphocytes that have not yet met their antigen
What happens to thymocytes that recognise self cells?
Apoptosed and cleaned up by Hassall’s corpuscles
What specifically do TCRs bind to?
foreign molecules that have been broken down into smaller peptides and presented via the MHC
process of t cell differentiation
double negative (do not express either CD4 or 8) then double positive and then either. CD3 and TCR expression also increases as it matures. takes 1-3 weeks
what do BCRs bind to?
the whole pathogen
lymphatic system
vessels of extracellular fluid. how lymphocytes and leukocytes move throughout the body
how do lymphocytes move throughout the blood?
bind to adhesion molecules on endothelial cells and roll along the vessel
efferent pathway
exit - out of the lymphatic system via the thoracic duct
afferent pathway
arrival - into the lymphatic system via HEV
lymphocyte homing
migration - the traffic of cells through the body to specific areas
lymph nodes structure
small, bean-shaped, tissue aggregates at junctions of major lymphatic vessels, surrounded by a capsule & supported by a reticulum
what are the three main areas of lymph nodes?
cortex, paracortical area, medulla
HEV
high endothelial venules
where do t and b cells collect in the lymph nodes?
t - paracortical
b - outer cortex (bind to antigens first since don’t need breaking down)
paracortical area
contains antigen presenting cells and large lymphocytes
medulla
contains plasma secreting antibodies
primary vs secondary follicles
Primary follicles are very dense & uniform
Secondary follicles contain larger cells associated with macrophages forming GERMINAL CENTRES with lots of cell proliferation
what happens after antigen exposure in lymph nodes?
increased lymphocyte turnover
why do lymph nodes swell during infection?
increased lymphocyte proliferation
spleen structure
Capsule with fibrous partitions (SEPTAE)
what are the two types of spleen tissue?
red and white pulp
Red pulp
Non-immunological role - filters damaged or aged red cells
White pulp
Immunological role – to develop immune
responses
PALS
PERIARTERIOLAR LYMPHATIC SHEATH - makes up white pulp of spleen, populated with T lymphocytes
spleen b-dependent area
lymphoid follicles
spleen t-dependent area
PALS
Examples of MALT
GALT and BALT
Structure of GALT
Peyer’s patches and isolated follicles in colonic submucosa, clusters/intraepithelial lymphocytes
Peyer’s patches
Aggregates of lymphocytes; B cells form central follicle surrounded by T cells & macrophages/antigen presenting cells, covered by microfold cells
microfold cells
selectively takes up antigens to deliver them to lymphoid follicles
BALT structure
consists of collections of mostly B cells organised into aggregates & follicles with few germinal centres, some M cells but organisation is less defined
