Lymphoid Flashcards
Affinity Maturation
Process by which B-cells produce anitbodies with increased affinity for antigen during the course of an immune response
Isotype Switching
Ig class switching (or isotype switching or isotypic communication or class switch recombination, is a biological mechanism that changes a B-cells production of antibody from one class to another
APC
antigen presenting cells - have MHC II on surface, phagocytic, dendritic cells
Components of innate immune system?
epithelial barrier and their secretions
- macrophages, granulocytes, NK cells
- non-specific
What is the specific immune system?
specific, cell-mediated. b-cells/t-cells manage humoral response
What provides specificity?
Immunoglobulin (ab) or T-cell receptors
What are the fundamental units of all antibodies
Two heavy, two light chains (constant region + antigen binding - Fab)
Initial antibodies on b-cells?
IgM, IgD
First Abs secreted by a recently formed plasma cell?
low affinity IgM
What is isotype switching?
cells resulting from colonal expansion of the original B-cell - affinity maturation and isotype sitchin
IgG - blood
IgM - secretions
IgE - allergens
What is the humoral response?
binding of antigen to Ab of B-cell
- antigen processed by B-cell and presented on MHC II
- T-helper cell recogizes and calls for the release of cytokines
- t-cell will then trigger a clonal expansion of b-cells
- plasma and memory b-cells produced
How do cytotoxic t-cells kill target cells?
lytic agents
Inside the capusle of the thymus, what are the portions of the thymic parenchyma
Medulla and Cortex
What makes up the stroma of the thymus?
Epithelioreticular cells (ERC)
there is no CT!!
What are ERCs?
secrete thymic hormones?
- ERC I = blood-thymus barrier
- ERC II = positive selection
- ERC III = barrier between cortex and medulla
- ERC IV = medullary sidde
- ERC V = neg selection
- ERC VI = hassall’s corpuscle
What are the function of lymph nodes?
- encapsulated secondary lymphoid organ that serves as a filter for antigens traveling in the lymphatics circulation
How does lymph traverse the node?
- afferent lymph pierce the capsule
- subcapsular sinus
- leaky lymphatic sinusoids (allow for percolation of lymph down cortex)
- subajacent paracortex
- medulla (medullary cords - surrounded by medullary sinuses)
- sinuses coalesce to form efferent
- leave node at hilum
Where in the node would you expect to find metastatic cells?
subcapsular space
What is a secondary follicle?
- primary follicles contain naiive lymphocytes
- upon encoutering their specific antigen they become active and proliferate
- secondary: clearing of central protion of follicle to form a germinal center
What are follicular dendritic cells?
antigen presenting cells
- sequester antigen to optimize llymphocyte-antigen interaction
What are in the medullary cords?
loose arrangement of
- lymphocytes
- plasma cells
- macrophages
- supportive reticular cells
What would you find in the red pulp?
sinusoids, macrophages, reticular CT, RBCS
What is white pulp?
aggregates of lymphocytes.
- lymphoid follicles (B-cells)
- PALS (t-cells)
Blood supply of the spleen?
- blood vessels enter in trabeculae
- central artery
- become ensheathed in layer of T-cells (PALS)
- also associated with b-cell follicle
- branches of central artery = penicillar arteries (open up into red pulp)
- splenic sinuses have a unique architecture (barre-stave, with surrounding reticular fibers to create seive for filter aged red blood cells)
