HEMATOPOIESIS III—IMMUNE SYSTEM & LYMPHOID ORGANS Flashcards
Name two general functions of the lymphoid system
- helps maintain fluid balance in the tissues of the body.
2. it has a major role in the defense against infection
function of lymphatic vessels
1) one way system to the heart
2) return of collected excess tissue fluid
3) return of leaked protein
How do lymph capillaries differ from blood capillaries?
- originate as pockets rather than continuous tubes -larger diameter with thinner walls
- flattened/IR outline in sectional view
- incomplete or absent basal lamina vessel walls= act as one-way mini valves allowing excess fluid, proteins, electrolytes, bacteria and viruses not to leave
- prominent ones located in most organs but absent in areas that lack blood supply (ie: cornea, bone marrow and CNS)
Two types of lymphatic collecting vessels
1) Superficial in subcutaneous layer deep to skin traveling with superficial veins (ie: areolar tissues of mucous membranes lining the digestive, respiratory, reproductive and urinary tracts)
2) Deep lymphatic vessels (larger) accompany deep arteries and veins to skeletal muscle, organs of the neck, limbs, trunk and walls of visceral organs.
Central Lymphoid Organs
thymus
bone marrow are involved in the production and early secretion of lymphocytes
What is autoimmunity?
is an immune reaction against self molecules
Peripheral Lymphoid Organs
lymph nodes and isolated cells found in the mucosa of the digestive system (tonsils, Peyer’s patches, appendix), the respiratory system, the reproductive system, and the urinary systems are collectively known as MALT (mucosa-associated lymphoid tissue) and considered a lymphoid organ.
What kind of immune response does the peripheral lymphoid organs elicit?
adaptive immune response
What is the significant of Waldeyer’s ring?
form a circle at the entrance of the gut and airway to initiate a immune response.
What are characteristics of Innate Response?
1) Pathogen specificity is broad and programmed in germline DNA
2) Macrophrages, neutrophils, eosinophils, and NK cells are directly involved with killing pathogens
3) Can lead to autoinflammation diseases
What are the two types of immune responses?
Innate (natural) repsonse and Adaptive Response
Antigen
molecule that is recognized by the cells of the immune system and may elicit a response.
Examples: May be soluble molecules (proteins, polysaccharides, and nucleoproteins) or molecules belonging to whole cells (bacteria, protozoa, tumor cells, or virus-infected cells).
Which response is the most primitive, responds to general classes of molecules?
Innate (natural)
Characteristics of adaptive repsonse:
Antigens Memory Cells Cell T Humoral- Antibodies Can recognize proteins, bacteria, tumor cells, virus-infected cells
Memory Cells
increase the speed and vigor of subsequent response
Ex: vaccinations work by inducing memory cell production
What is the adaptive immune response dependent on?
lymphocytic recognition of antigens
Which is the faster immune response?
innate
What is autoimmune disease a result of:
adaptive immune responses to self-antigens.
Two mechanisms of auto immune response
1) Cell T 2) Humoral
antibodies belong to which family?
antibodies = immuninoglobulin (Ig) family & combine with a specific antigen
Two types of antibodies
Free- circulate in plasma, leave vessels to tissues or present in the secretion of some epithelia
Not free- integral membrane proteinson the surface of lymphocytes
What is the role of T cells?
primarily in charge of eliminating the antigen. Directly kill infected cells or activate macrophages
What runs the humoral response?
antibodies
What do B lymphocytes differentiate into?
plasma cells
What do plasma cells secrete?
antibodies
Immunocompetent cell
cell involved in the immune response that is fully mature and functional. Performs its role by recognizing and responding to antigens
What are functions of the APC?
1) Determines the fate of T cells
2) Promotes cellular or humoral immunity
3) Enhance or suppress response to antigen
Name the development and maturation sites for B lymphocytes
1) develop from CFU-L stem cells (lymphoid colony forming unit - common lymphoid progenitor) in the bone marrow
2) DNA rearrangement and somatic mutation to generate alleles for antibody diversity
3) non responding cell or unfunctioning antigens are eliminated
4) leave the bone marrow &circulate via lymph and blood
5) develop peripheral tolerance – additional receptor editing or cell elimination to reduce autoreactivity
6) maturation and travel to secondary lymphoid tissues, e.g., lymph node
Name the development and maturation sites for T lymphocytes
1) develop from CFU-L progenitor cells in the thymus
2) DNA rearrangements & somatic mutations (antigen diversity)
3) circulate among secondary lymphatic tissues
4) proliferate and differentiate into one of several effector or memory cell types in response to its specific antigen in a complex with an antigen-presenting cell.
What are functions of plasma cells?
Secrete antibodies:
1) Block the activity of an antigen
2) Mark the antigen for phagocytosis
3) Activate the complement system which directly kills some bacteria and activates cells of the innate immune system
what are the Primary/Central lymphoid tissues and its function?
bone marrow & thymus
-sites of antigen-independent lymphocyte generation and differentiation (bone marrow for B cells and thymus / bone marrow for T cells).
Oppositive of immunocompotent cell and some examples?
immunodeficient or immunocompromised = newborns, AIDs patient, or transplant patient
Antigen-Presenting Cell (APC)
form complexes with T cells that include a peptide from the specific antigen recognized by the T cell as well as several cell surface proteins
What are characteristics of peripheral lymphoid tissue?
tissues in which antigen-dependent, adaptive immune responses are initiated and the lymphatic vessels that connect them to other tissues and the blood stream.
Peripheral lymphoid tissues include:
lymph follicles (nodules), lymph nodes, the spleen, and lymphatic vessels
Examples of confluent nodules, partially and fully encapsulated nodules.
Peyer’s Patches / appendix –> confluent
Tonsils –> confluent, partially encapsulated
Spleen / lymph nodes –> fully encapsulated
Lymphoid nodules are collectively known as
MALT
What are functions of a lymph node?
1) Filters lymph; all lymph passes through at least one lymph node before entering blood stream
2) Removes foreign substances, microorganisms, cancer cells from lymph
what does MALT stand for and the different types:
MALT: Mucosa-Associated Lymphoid Tissue (GALT- gut; BALT; bronchus; CALT; conjunctiva)
Function of the spleen
1) Filters blood to remove damaged, worn-out cells (lymph nodes filter lymph; spleen filters blood)
2) Activates immune responses to substances and microbes in the blood
Functions of lymph vessels
1) Connects parts of lymph system to the blood and vasculature
2) Carries fluid and lymphocytes from lymph nodes to veins
3) Carries fluid and antigen-bearing cells from most tissues to lymph nodes
4) Connects chains of lymph nodes
5) Critical for maintaining balanced tissue fluid flow 6) Destruction of Erythrocytes: Macrophages in the splenic cords engulf and digest the erythrocytes that frequently fragment in the extracellular space.
Afferent lymphatic vessels
drain lymph INTO the lymph node; pass through the capsule of lymph node; several located on each node
Follicular Cortex (Outer Cortex)
B CELL ZONE–>Superficial cortex; contains many primary and secondary germ lymphatic nodules containing B-cells
Parafollicular Cortex (paracortex)
T-CELL ZONE –>location of T-lymphocytes and APC
Medulla
contains B and T cells: central portion of the lymph node; location of medullary cords and medullary sinus
Cortical Sinuses
lymph passes through cortical sinuses after enter via afferent vessel; dendritic cells and macrophages present to phagocytize lymph content
Medullary cords
macrophage rich area; contains plasma cells that secreted enriched antibodies
collect lymph that has filtered through cortex; Drains into efferent lymphatic vessels
Name a place where antigen and antigen-specific lymphocytes have a high probability of crossing paths to initiate an immune response
Lymph Nodes
Efferent lymphatic vessels
drain lymph OUT of lymph node; located at the hilum; can drain into circulatory system or another lymph node
Identify T and B cell-rich zones in the lymph node cortex
Outer=B-cells
Deep and Inner =T-cells
Red pulp
-Composed of splenic cords and sinusoids (RBCs)
-Macrophages - engulf damaged cells or foreign
Plasma cells for antibodies
ALL blood cells
White pulp
lymphoid tissue –>
-PALS (which consists mostly of Tcells)- central artery and the peripheral white pulp (consisting mostly of Bcells). The nodule is surrounded by marginal zone sinuses= APC trafficking
What is the Largest secondary lymphoid organ?
Spleen
Splenic sinusoids
separate the splenic cords. Elongated endothelial cells line the sinusoids of the spleen with the long axes parallel to the long axes of the sinusoids.
Main function of the thymus
T-cell maturation (“education” – they learn how to differentiate self from non self) – most active before puberty then the thymus begins to atrophy into adulthood
NO B cells; NO follicles
medulla
T cells!
Epithelial reticular cell stroma
fewer lymphoid cells, contains Hassal’s corpuscles
Hassal’s corpuscle
in the medulla; composed of concentric circles of epithelial –> aid in T-cell maturation
Medullary Sinuses-
provide network through medullary sinus that lymph must pass through in medulla before reaching the efferent lymphatic vessel
Splenic cords
contain a network of reticular cells and is supported by reticular fibers. They contain T and B lymphocytes, macrophages, plasma cells and many blood cells (erythrocytes, platelets, and granulocytes).
Components of the thymus:
Blood thymus barrier, cortex, medulla, Hassal’s corpuscle
blood thymus barrier
barrier that regulates what substances can get into the thymus—prevents immature T-cells from coming into contact with foreign antigens too early
cortex
composed of lymphoid cells
red pulp contains?
platelets, granulocytes, RBCs, plasma
white pulp contains?
lymphocytes and T cells
