Tissues and Organs of the Immune System (Week 3) Flashcards
lymphatic system
- network of vessels with lymph (fluid
derived from blood plasma) - Lymph vessels also return fluid
that leaked from capillaries to
the bloodstream
Thoracic duct
- largest lymph vessel, drains into bloodstream
- moves plasma back in to circulatory system
Immune cells and the lymphatic system
- use this system for transport (primary done by lymphocytes)
- they are recruited from blood vessels to the site of infection (vascular permeability) and then “drain” or travel, along with antigen, to secondary lymphoid organs
What are cytokines and chemokines for?
they let the immune cells know where to go
Cytokines
- recruitment and travel
- Recruit nearby immune cells with the specific cytokine receptor
- Enhance the immune cell function
Chemokines
- directionality
- use chemokine gradients to help immune cells enter or exit certain tissue
- Recruit cells with specific chemokine receptor out of the bloodstream and into infected tissue
- organize the various cells in lymphoid tissues into discrete regions where specialized responses can take place
Lymph nodes
- secondary lymphoid tissue
- house a lot of lymphocytes
- where lymphocytes first encounter antigen
- highly specialized in regulating immune responses
Cortex (lymph nodes)
- outermost tissue layer
- contains B cells (Follicle)
- Macrophages and DCs (resident and migrating)
Paracortex (lymph nodes)
- Middle tissue layer
- T cells (T cell zone)
- Macrophages and DCs (resident and migrating)
Medulla
- Innermost tissue layer
- Plasma cells
Travel through the lymph nodes
- Antigen and immune cells enter the lymph node through incoming (afferent) lymphatic vessel in the cortex
- Exit from the outgoing (efferent)
lymphatic vessel in the medulla - Immune cells enter from the blood by the high endothelial venule (HEV) (blood vessel in the lymph nodes)
Fibroblastic reticular cell conduit
(FRCC)
- guides T-cells in the lymph nodes
- fibroblastic reticular cells (FRCs) make up the network
- antigens position themselves on this
Follicular dendritic cell network
- made up of follicular dendritic cells (FDCs)
- guides B cells in the lymph nodes
germinal centers
Spleen
- secondary lymphoid tissue
- coordinates immune responses
towards bloodborne pathogens - has no lymphatic vessels
- red pulp surrounds white pulp separated by the marginal zone
Red pulp
- contains red blood cells,
macrophages, and some lymphocytes - Site where old and defective red blood cells are destroyed and removed
White pulp
- Consists of B-cell follicles and
the periarteriolar lymphoid sheath (PALS) - populated by T lymphocytes
Marginal zone
specialized dendritic cells,
macrophages, and unique MZ B cells
Barrier tissues
- secondary lymphoid tissue
- Epithelial cells secrete cytokines, chemokines and antimicrobial compounds
- Immune cells reside in deeper
layers of the tissue - Mediate pathogen responses
and maintain tolerance to
commensal microbes - B cell follicles and germinal centers form to produce plasma cells and antibodies
M cells
specialized epithelial cells in GALT (Gut-associated lymphoid tissue) passing antigen from intestinal lumen
to intestinal wall (lamina propria)
What helps distinguish pathogens from commensal microbes in barrier tissues?
Macrophages, DCs, Tregs and
Intraepithelial lymphocytes
(IELs)
Tertiary lymphoid structures
- Immune cells that recognize antigen in lymph nodes, return to organs (tertiary lymphoid tissue) as tissue-resident cells and form organized lymphoid structures
- “Inducible lymphoid tissue” in response to chronic inflammation or cancer
