Flashcards in Lymphoid 1 Deck (33):
Types of innate immunity (2)
1) Physical and chemical barriers
2) Cells that destroy non-specifically
Types of cells involved in non-specific innate immunity
3) NK cells (natural killer)
Three characteristics of acquired immunity
2) adaptive - will not respond until antigen is encountered
Two major functional types of lymphocytes
if a lymphocyte has never encountered its antigen then it has what three properties?
B lymphocytes are responsible for what type of immunity? What do they do when activated?
turn into plasma cells for the secretion of antibodies
name two classes of antibodies and a special feature of each
IgA - withstands mucosal environments
IgE - binds mast cell IgE receptor/antigen binding causes degranulation
features of antibody structure
1) composed of a 2 heavy chains and 2 light chains
2) light chains are binding domains
3) base of "Y" is the Fc region for immune binding
T-lymphocytes do what? (generally) what do they react to?
carry out cell mediated immunity
they react to cell bound antigen (not free antigen)
types of T cells (3)
cytotoxic T cells - kill cells directly when receptor is bound (important for virus defense)
helper T cells - secrete paracrine cytokines
regulatory T cells - inhibit immune response with cytokines
possible functions of helper T cells (3)
1) effector cells - recruit macrophages to generate immune inflammatory reactions
2) support cytotoxic T cell generation
3) promote activation of B cells and humoral immunity
Phases of immune response
1) cognitive phase - recognition
2) activation phase
3) effector phase - clearance
receptor composition on B cells and T cells
B cells express antibodies
T cells are more complex but still singularly specific and recognizes antigen bound in a particular way to cellular surfaces
activation phase of immune response (generally)
effectors (T&B cells) are produced; takes place in lymphoid organs
characteristics of APC cells (3)
1) presentation of the antigen to T cells by Antigen Presenting Cell (APC)
2) primarily dendritic cells; present in the epithelium but drain to lymphatics via lymphatic drainage (abundant in lymphoid tissue)
3) macrophages can serve as APC's as well, though not as efficiently
activation phase steps (5)
1) expansion of responsive cells by cloning those with the appropriate antibody (all steps are specific - only those with the appropriate antibody are produced)
2) activation of T cells by APC
3) activation of B cells by differentiation
4) Th cells activated to produce cytokines to positive feedback loop the creation of B cells and Tc cells
5) some progeny of B and T cells differentiate into memory cells
what are the stages of the activation phase referenced via the activation of Th cells?
Naive Th gets activated by an antigen presenting cell (APC);
this activates the Th which then releases a set of cytokines that have three effects
1) activation of naive B cells into plasma cells to secrete antibodies
2) activation of Tc cells (that may have been exposed to the APC)
3) activation of inflammatory response
what happens during the EFFECTOR phase?
clearance of the antigen; importantly, this occurs in the periphery
what problems are posed by the SPECIFICITY of lymphocytes?
antigens can enter the system at any point, but there are not many circulating lymphocytes with that specific antibody attached;
therefore, bringing the appropriate lymphocyte/antibody combination together with its specific antigen (and all in the presence of an APC) can take time
what are the two types of LYMPHOID ORGANS? what is the difference? examples of each?
primary - where naive B and T cells are manufactured - thymus and bone marrow
secondary - where the activation and effector phases are carried out; lymph nodes, spleen and mucosal lymphoid tissue
characteristic composition of SECONDARY lymphoid tissue
1) many APC cells present to activate naive cells
2) antigens may get trapped here because these are locations for epithelial, blood and lymph filtration
3) lymphocyte recircultion - lymphocytes preferentially stay in these areas in order to maximize the chance that they will encounter the antigen that they are programmed to respond to
what are the three types of lymphatic sinuses found in lymph nodes? what is the direction of flow and what are the vessels called?
(from inside out)
1) medullary sinus
2) intermediate (trabecular) sinus
3) subcapsular sinus
flow goes in the opposite direction (up this list), from an afferent vessel to the efferent vessel
what types of cells can be found in the parafollicular (deep cortex) region? at the follicular (outer cortex) region? which is located closer to the hilum?
Parafollicular region contains T cells & APC cells, B cells can be found at the follicular region with some T cells. (PT Boat); the parafollicular region is closer to the hilum
what provides ECM support for the stroma of secondary lymphoid organs? what functions does this network have? what provides support for the capsule and trabeculae?
reticular cells (type III collagen network); it provides the means for antigens to move across the node and produces factors important for organization of the node;
structural support for the capsule and trabeculae is provided by type I collagen
what comprises a germinal center? color? type of cells located here (6)?
it is a pale-looking central area in a follicle (outer cortex) that is also called a secondary follicle.
B cell activation is happening here but not complete maturation to plasma cells
It is composed primary of cells that are undergoing differentiation, proliferation, apoptosis and macrophages that are digesting those cells that are undergoing apoptosis
there are also non - APC dendritic cells in the germinal center; these are called follicular dendritic cells
what's going on in the deep cortex? (Parafollicular area)
This is where T cells are activated
APC's accumulate here (cannot be distinguished from reticular cells without special stain)
What are the two components of the medulla?
The sinuses and the cords
What do you see inside the sinuses?
reticular cells, immature plasma cells and lymphocytes
What can be found inside the cords?
veins (arteries are located in the trabeculae)
how is lymph flow altered to maximize presentation of antigens to lymphocytes?
lymph flow is baffled by reticular fiber network
flow is allowed to pass through tissue or through the sinuses
APCs carrying antigens are concentrated in the deep cortex, a denser area of the node
macrophages accumulate at the entrance and exit of the node (subcapsular sinus and medullary cords)
how do lymphocytes get into the node?
mostly through diapedesis through the blood vessels (esp. naive lymphocytes); specifically through the high endothelial venules (tall endothelial cells) in the post capillary venules (PCV)
some delivered through the afferent lymph vessel
where are the two main locations to find mucosal lymphoid tissue?
bronchial system and gut
tonsils, appendix and Peyer's patches in ileum