Immunity Flashcards
composed of lymphatic vessels that trans- port interstitial fluid (as lymph) back to the blood circulation
lymphatic system
Primary lymphoid organs
bone marrow and thymus
where B and T lymphocytes are formed
bone marrow and thymus
secondary lymphoid organs
lymph nodes, MALT, and spleen
Haemophilus influenzae and Streptococcus pneumoniae, avoid phagocytosis by granulocytes and macrophages of ___ by covering their cell walls with a “capsule” of polysaccharide
innate immunity
Growth and differentiation factors for leukocyte progenitor cells in bone marrow
GM-CSF, M-CSF
Stimulation of inflammation and fever
TNF-α, TGF-β, IL-1
Stimulation of growth in T lymphocytes and NK cells
IL-12
Growth factors for T helper cells and B lymphocytes
IL-2, IL-4
Eosinophil proliferation, differentiation, and activation
IL-5
Activation of macrophages
Interferon-γ, IL-4
Inhibition of macrophages and specific adaptive immune responses
IL-10
Antiviral activity
Interferon-α, interferon-β
Chemokine for neutrophils and T lymphocytes
IL-8
- monomer
- 75% - 85%
- fetal circulation in pregnant women
- Activates phagocytosis, neutralizes antigens
IgG
- pentamer
- 5%-10%
- B lymphocyte surface (as a monomer)
- First antibody produced in initial immune response; activates complement
IgM
- dimer with J chain and secretory component
- 10%-15%
- secretions (saliva, milk, tears, etc)
- Protects mucosae
lgA
- monomer
- 0.001%
- Surface of B lymphocytes
- Antigen receptor triggering initial B cell activation
lgD
- monomer
- 0.002%
- Bound to the surface of mast cells and basophils
- Destroys parasitic worms and participates in allergies
lgE
Antibody covers biologically active portion of microbe or toxin.
neutralization
Antibody cross-links cells (eg, bacteria), forming a “clump.”
agglutination
Antibody cross-links circulating particles (eg, toxins), forming an insoluble antigen-antibody complex
precipitation
Fc region of antibody binds complement proteins; complement is activated.
complement fixation
Fc region of antibody binds to receptors of phagocytic cells, triggering phagocytosis.
opsonization
Fc region of antibody binds to an NK cell, triggering release of cytotoxic chemicals.
activation of NK cells
- 100% T lymphocytes
- 0% B lumphocytes
thymus
- 10% T lymphocytes
- 90% B lumphocytes
bone marrow
- 45% T lymphocytes
- 55% B lumphocytes
spleen
- 60% T lymphocytes
- 40% B lumphocytes
lymph nodes
- 70% T lymphocytes
- 30% B lumphocytes
blood
- Tissue grafts and organ transplants are classified as ___ when the donor and the host are the same individual
- burn patient for whom skin is moved from an undamaged to the damaged body region
autografts
involving identical twins
isografts
involve two related or unrelated individuals, consist of cells with MHC class I molecules and contain dendritic cells with MHC class II molecules
Homografts (or allografts)
inhibit the activation of cytotoxic T cells
cyclosporins
CD4 binds with MHC class II molecule of APC; TCR interacts with antigen within MHC class II molecule.
first stimulation
Helper T lymphocyte releases IL-2, which stimulates the helper T lymphocyte.
seconf stimulation
CD8 binds with MHC class I molecule of various cells; TCR interacts with abnormal antigen within MHC class I molecule.
first stimulation
IL-2 released from activated helper T lymphocyte stimulates the cytotoxic
T lymphocyte.
second stimulation
Failure of the third (and fourth) pharyngeal pouches to develop normally in the embryo
DiGeorge syndrome
Lacking many or all thymic epithelial cells, such individuals cannot produce T lymphocytes properly and have severely depressed cell-mediated immunity
thymic hypoplasia
Free antigen binds to BCR; B lymphocyte engulfs, processes, and presents antigen to activated helper
T lymphocyte.
first stimulation B lymphocyte
IL-4 released from activated helper T lymphocyte stimulates B lymphocyte.
second stimulation B lymphocyte
a bilobed organ located in the superior mediastinum, is most prominent and active before puberty, undergoing gradual shrinkage (involution) and loss of activity in adults.
thymus
- survival dependent on ability to bind to MHC molecule
- occurs in the cortex and allows survival only of T cells with functional TCRs recognizing MHC class I and class II molecules
positive selection
- Survival dependent on not recognizing self-antigen
- occurs in the medulla and allows survival only of T cells that do not tightly bind self-antigens presented on dendritic cells there
negative selection
located in the posterior lateral walls of the oral cavity
palatine tonsils
situated along the surface of the posterior third of the tongue
lingual tonsils
- single medial mass situated in the posterior wall of the nasopharynx
- covered by ciliated pseudostratified columnar epithelium
pharyngeal tonsil
Hypertrophied regions of pharyngeal tonsils resulting from chronic inflammation are called
adenoids
- Inflammation of the tonsils
- more common in children than adults
tonsillitis
- Chronic inflammation of the pharyngeal lymphoid tissue and tonsils of children often produces hyperplasia and enlargement of the tonsils to form
- obstruct the eustachian tube and lead to middle ear infections
adenoids
encapsulated structure filled with lymphocytes, a condition
lymphadenopathy
- Enlargement of the spleen
- The splenic capsule is relatively thin, and an enlarged spleen is susceptible to traumatic rupture, a potentially life-threatening occurrence due to loss of blood into the abdominal cavity
splenomegaly
surgical removal of the spleen
splenectomy
Thymus: distinctly present
MALT: absent
Lymph Nodes: present
Spleen: absent
cortex/medulla
Thymus: absent
MALT: present
Lymph Nodes: present (in cortex only)
Spleen: present (in white pulp only)
lymphoid nodules
Thymus: no afferents; few efferents in septa
MALT: no afferents; efferents present
Lymph Nodes: Afferents at capsule, emptying into subcapsular sinus; efferent at hilum
Spleen: No afferents; efferents in trabeculae
lymphatic vessels
Hassall (thymic) corpuscles in medulla; epithelial- reticular cells in cortex and medulla
thymus
crypts lined by surface mucosa in tonsils; epithelial M cells in mucosa over Peyer patches
malt
Thin paracortical region between cortex and medulla, with high endothelial venules (HEV); medullary cords and sinuses
lymph nodes
Minor white pulp component, with central arterioles; major red pulp component, with many sinusoids
spleen
present from birth and involves leukocytes (mainly granulocytes) and proteins such as defensins, complement, lysozyme, and interferons
innate immunity
develops more slowly and is based on antigen presentation to lymphocytes
adaptive immunity
Immune cells communicate with one another and regulate one another’s activities via polypeptide hormones called
cytokines
regions of macro molecules, usually proteins, that are recognized by lymphocytes to elicit a specific immune response
against them
antigens
immunoglobulins produced by plasma cells after a progenitor B cell is activated by a specific antigen and rearranges its
immunoglobulin genes so that the antibody matches the antigen
antibodies
surfaces of all nucleated cells bear fragments of their constituent
proteins on ___ molecules
MHC class I
Lymphocytes originate in the
primary lymphoid organs
bone marrow for
B lymphocytes
thymus for
T lymphocytes
B cells produce antibodies for
humoral immunity
T cells function in
cell-mediated immunity
bind antigen along with another surface protein designated by a CD (“cluster of differentiation”) numbering system
t cells develop receptors (TCR)
CD4+ T helper cells; CD8+ cytotoxic T cells; CD4+CD25+ regulatory T cells; and γδ T cells
classes of T cells
IgM or IgD antibodies on the cell surface that bind specific antigens whenever they contact them
b-cell receptors (BCR)
B and T cells are often activated, proliferate, and begin to function in the
secondary lymphoid organs
secondary lymphoid organs
lymph nodes, all MALT, and the spleen
a FDC-activated B cell proliferates clonally to produce temporarily a large ___ (or follicle), which develops a pale germinal center
lymphoid nodule
cells produced there disperse as plasma cells, various T cells, and B and T memory cells that respond and proliferate quickly if their specific antigen reappears
lymphoid nodules
attach in the thymus to a cytoreticulum composed of interconnected TECs
t lymphoblasts or thymocytes
producing functional T cells that do not bind to proteins of the host
central immune tolerance
occurs throughout the body when specific immune reactions are suppressed by regulatory T cells that also originate largely in the thymic medulla
peripheral immune tolerance
Regulatory T cells form in the thymus upon interacting with dendritic cells presenting self-antigens in a process promoted by cytokines from thymic epithelial cell (TEC) aggregates called ___
Hassall corpuscles
found in the mucosa of most tracts but is concentrated in the palatine, lingual and pharyngeal tonsils, Peyer patches, and the appendix
MALT
completely encapsulated and occur along the lymphatic vessels; each has several afferent lymphatics and one efferent lymphatic.
lymph nodes
A lymph node has three functional but not physically separate compartments
cotex, paracortex, medulla
Most lymphocytes enter at the ___ of the lymph node via HEVs located there only; most lymphocytes in this region are T helper cells
paracortex
The medulla has ___ containing reticular fibers with many plasma cells, macrophages, and other leukocytes
medullary cords
- large lymphoid organ without a cortex/medulla structure
- two intermingled but functionally different regions: white pulp and red pulp
spleen
- 20% of the spleen
- secondary lymphoid tissue associated with small central arterioles that are also enclosed by PALS of T cells
white pulp
filters blood, removes defective erythrocytes, and recycles hemoglobin iron, consists of splenic cords with macro- phages and blood cells of all kinds and splenic sinusoids
red pulp
lined by unusual endothelial cells called stave cells
splenic sinusoids
elongated and aligned parallel to the blood flow, with open slits between the cells
stave cells
Blood flow in red pulp is either a ___, moving from capillaries into the venous sinusoids
closed circulation
capillaries opening directly into the splenic cords
open circulation
- Blood filtration in the open circulation involves interaction with splenic cord ___
- remove old, swollen RBCs unable to slip between stave cells to reenter the venous blood flow
macrophages
Which function is carried out by all lymphoid tissues and organs?
Production of lymphocytes
Which structure is partly encapsulated and covered by nonkeratinized stratified squamous epithelium?
Palatine tonsil
Which cell type gives rise to both memory and effector cells and is primarily associated with humoral immunity?
B lymphocyte
Recycling of iron and heme, the major complex containing iron, occurs most actively in which lymphoid organ(s)/tissue(s)?
Spleen
Which description is true of all secondary (peripheral) lymphoid organs?
Contain lymphoid nodules
Which structure would be most heavily labeled by an immunohistochemical method targeting the CD8 surface antigen?
Paracortex
A baby is born with a cleft palate and a condition called DiGeorge syndrome, which involves failure of third and fourth pharyngeal pouch derivatives to develop properly. The palate defect is corrected surgically, but regarding the pharyngeal pouch defect the parents are advised that the growing child may expect which of the following health problems?
Conditions related to autoimmunity
Many immune-related cellular activities are often impaired in aged patients. Which lymphoid organ(s) normally develop less functionality and increasing amounts of adipose tissue with age?
thymus
A 12-year-old girl of African descent presents with anemia and a large percentage of her peripheral erythrocytes appear sickle-shaped. Genetic testing reveals homozygosity for sickle cell disease. In which of the following sites will the abnormal RBCs be removed from the circulation?
Splenic cords (of Billroth)
A 6-year-old boy is brought to the clinic where his mother reports that he was bitten by a neighbor’s dog two days earlier. The child’s right hand is lacerated between the thumb and index finger and this area is inflamed but healing. The doctor’s examination reveals small but pain- less swellings beneath the skin inside the right elbow and arm pit and he explains to the mother that these are active lymph nodes enlarged in response to the infection in the hand. What has produced the swelling?
Formation of germinal centers for B-cell proliferation in each
node’s cortex
