Buscar
Estás en modo de exploración. debe iniciar sesión para usar MEMORY

   Inicia sesión para empezar

level: Consolidation Assignment 6

Questions and Answers List

level questions: Consolidation Assignment 6

QuestionAnswer
what are the secondary lymphoid organs and tissues? where are they located?lymph nodes: throughout the body spleen: underneath the left part of the diaphragm mucosa-associated lymphoid tissue (MALT): throughout the body in submucosal sites; GI and respiratory tract, thyroid, breast, eye, skin
what is the structure of a lymph node and which cells are present where?cortex: outer layer containing mainly B cells in follicles paracortex: middle layer containing mainly T cells and DCs medulla: inner layer containing some B and T cells and plasma cells
how does the lymph fluid flow?into the lymph node -> subcapsular sinus -> cortical sinuses -> cortex -> medullary sinuses -> efferent lymph vessels -> out of the lymph node
describe the structure of the spleen and where the lymphoid cells are locatedthe spleen consists out of trabecular arteries organized in a network of channels called sinusoids. the spleen has red and white pulp; red pulp: storage of red blood cells white pulp: arterioles surrounded by lymphoid cells. T cells surround the arteriole in periarteriolar lymphoid sheaths (PALS) and B cells are located in follicles
which cells are present in follicles? what happens in there?naive B cells located in follicles clonal expansion, proliferation and differentiation (isotype switching) takes place -> the naive B cells become plasma or memory cells
which tissues/organs belong to MALT?GALT -> gut (Peyer's patches, appendix) BALT -> bronchus NALT -> nasal (tonsils) CALT -> conjunctival LALT -> larynx SALT -> skin VALT -> vagina TALT -> testis
what are Peyer's patches, where are they located and what are they characterized by?Peyer's patches are lymphoid follicles located in the small intestine. they are characterized by follicle-associated epithelium (FAE) and M cells
what is the function of M cells and where are they located?M cells or microfold cells are active in the GI tract. their function is to bring microbes from the lumen to the lymphoid tissue in the epithelium.
what is the function of regulatory T cells and how is this done?to suppress the immune response to not harm commensal bacteria this is done by; - production of cytokines that inhibit activation of lymphocytes - expressing CTLA-4 which block B7 molecules -> APCs cannot costimulate the T cells and T cells will not be activated - binding to T cell growth factor, reducing the availability for the T cells
what is the most important cytokine for the functioning of regulatory T cells?IL-2 (also important is TNF-beta)
what structures are present in the red and white pulp?red pulp: sinusoids, splenic cords, marginal zone (which is the outer edge) white pulp: malpighain corpuscles with B and T cells
how do naive T cells migrate into the lymph nodes?1. rolling adhesion on high endothelial venules (HEVs) mediated by L-selectin 2. chemokines (CCL19, CCL21) from lymph node attach to CCR7 on the T cell 3. CCR7 activates leukocyte function-associated antigen 1 (LFA-1) on the T cell 4. binding affinity of LFA-1 to ligand ICAM-1 on endothelium is increased 5. firm binding 6. T cell exists the vessel through junctions into the lymph node
how do T cells migrate out of the lymph nodes?naive T cell: following the gradient of SIP into the lymph fluid effector T cell: SIP receptor is reexpressed after differentiation, T cells loose L-selectin and CCR7 expression and follow the gradient of SIP into the lymph fluid
how do effector T cells migrate to the site of infection?1. high levels of E- and P-selectin and integrins LFA-1 and VLA-4 are expressed on the T cell 2. the cytokine produced by the innate response (TNF, IL-1) act on endothelial cells to increase expression of E- and P-selectin and integrin ligands 3. rolling adhesion occurs 4. T cells express receptors for chemokines produced by the infection, this increases binding affinity and causes firm adhesion to the endothelium 5. T cells enter the tissue through the junctions 6. T cells follow chemokines to infection
why are naive T cells unable to enter the site of infection?they do not express E- and P-selectins or receptors that can bind the chemokines produced at an infection
why can't effector T cells enter the lymph nodes?they do not express CCR7 or L-selectin, which is needed for attachment of chemokines and rolling adhesion respectively