Ch 14: Immune System / Lymphoid Tissues & Q Bank Flashcards
BASIC IMMUNITY
2 types:
Innate immunity is present from birth and involves leukocytes (mainly granulocytes), and proteins such as defensins, complement, lysozyme, and interferons; adaptive immunity develops more slowly and is based on antigen presentation to lymphocytes.
BASIC IMMUNOLOGY
Immune cells communicate with one another by….
and regulate one another’s activities via polypeptide hormones called cytokines.
BASIC IMMUNOLOGY
What are Antigens?
They are the regions of macromolecules, usually proteins, that are recognized by lymphocytes to elicit a specific immune response against them.
BASIC IMMUNOLOGY
Antibodies are immunoglobulins produced by plasma cells after a progenitor B cell is activated by….
a specific antigen and rearranges its immunoglobulin genes so the antibody matches the antigen.
BASIC IMMUNOLOGY
Surfaces of all nucleated cells bear fragments of their constituent proteins and placed on…
on major histocompatibility complex (MHC) class I molecules.
BASIC IMMUNOLOGY
Only antigen-presenting cells (APCs), mostly derived from monocytes, also present…
fragments of endocytosed foreign (usually from microorganisms) proteins on surface MHC class II molecules.
LYMPHOCYTE ORIGINS AND DIFFERENTIATION
There are 2 kinds:
Where do they originate from?
Lymphocytes originate in the primary lymphoid organs: bone marrow for B lymphocytes and the thymus for T lymphocytes.
Lymphocyte Origins and Differentiation
While B cells produce antibodies for humoral immunity
T cells function in cell-mediated immunity.
Lymphocyte Origins and Differentiation
How do T Cells work?
T cells develop receptors (TCRs), usually containing α and β chains, that bind antigen along with another surface protein designated by a CD (“cluster of differentiation”) numbering system.
Lymphocyte Origins and Differentiation
There 4 class’s of T cells
List them:
- CD4+ T helper cells;
- CD8+ cytotoxic T cells;
- CD4+CD25+ regulatory T cells;
- and γδ T cells, which have those TCR chains and are mainly in epithelia.
Lymphocyte Origins and Differentiation
B-cell receptors (BCRs) are IgM or IgD antibodies on the cell surface that
bind specific antigens whenever they contact them.
Lymphocyte Origins and Differentiation
B and T cells are often activated, proliferate, and begin to function in the secondary lymphoid organs: Which are:
- the lymph nodes,
- all mucosa-associated lymphoid tissue (MALT),
- and the spleen.
Lymphocyte Origins and Differentiation
In these organs, lymphocytes are distributed within a meshwork of reticulin produced by
fibroblastic reticular cells,
and most APCs are dendritic cells with many processes.
Lymphocyte Origins and Differentiation
In secondary lymphoid tissues, BCRs bind antigen not
presented in MHC class II molecules of another cell, which are the follicular dendritic cell (FDC).
Lymphocyte Origins and Differentiation
With cytokines from helper T cells, a FDC-activated B cell proliferates clonally to
produce temporarily a large lymphoid nodule (or follicle), which develops a pale germinal center.
Lymphocyte Origins and Differentiation
From lymphoid nodules cells produced, there dispersed as plasma cells, various T cells, and B and T memory cells that…
respond and proliferate quickly if their specific antigen reappears.
Thymus
T lymphoblasts, or thymocytes, attach in the thymus to a
cytoreticulum composed of interconnected thymic epithelial cells (TECs).
Thymus
The thymic epithelial cells (TECs) also secrete many cytokines, and compartmentalize the thymus into a cortex and a medulla, and
in the cortex, surround blood vessels in the blood-thymus barrier.
Thymus:
Developing T cells with nonfunctional TCRs are detected and removed in the thymic cortex by
a process of positive selection; cells with functional TCRs move into the thymic medulla.
Thymus
In the thymic medulla, T cells whose TCRs bind strongly to “self-proteins,” including proteins of many nonthymus cell types made by thymic epithelial cells expressing the Airegene,
are induced to undergo apoptosis there in a process of negative selection.
Thymus
This two-stage thymic selection leads to central immune tolerance, that
produces functional T cells that do not bind to proteins of the host.
Thymus
Peripheral immune tolerance occurs throughout the body when….
specific immune reactions are suppressed by regulatory T cells that also originate largely in the thymic medulla.
Thymus:
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 only in the thymic medulla.
Mucosa-Associated Lymphoid Tissue (MALT)
MALT is found in the mucosa of most tracts but is concentrated most in
the palatine, lingual and pharyngeal tonsils, Peyer patches, and the appendix.
Mucosa-Associated Lymphoid Tissue (MALT)
Unlike MALT, lymph nodes are completely encapsulated and occur
along the lymphatic vessels; each has several afferent lymphatics and one efferent lymphatic.
Lymph Nodes
Each lymph node filters lymph and provides a site for B-cell activation and
differentiation to antibody-secreting plasma cells.
Lymph Nodes
A lymph node has three functional but not physically separate compartments:
an outer cortex,
a underlying paracortex,
and an inner medulla adjacent to the hilum and efferent lymphatic.
Lymph Nodes
Lymphatics enter at the cortex of a node,
where B cells encounter antigens, and then
proliferate into lymphoid nodules, and then
move into the deeper regions of the lymph node.
Lymph Nodes
Most lymphocytes enter at the paracortex of the lymph node via high endothelial venules (HEVs) located there only;
most lymphocytes in this region are T helper cells.
Lymph Nodes
The medulla has medullary cords containing reticular fibers with many plasma cells, macrophages, and other leukocytes; between the cords are
lymph-filled medullary sinuses that converge at the efferent lymphatic.
Spleen
The spleen is a large lymphoid organ without a cortex/medulla structure;
instead, it has
two intermingled but functionally different regions:
white pulp and red pulp.
Spleen
White pulp, only 20% of the spleen,
is secondary lymphoid tissue associated with
small central arterioles that are also enclosed by
periarteriolar lymphoid sheaths (PALS) of T cells.
Spleen
Red pulp, which filters blood, removes defective erythrocytes, and recycles hemoglobin iron, consists of
splenic cords with macrophages and blood cells of all kinds and splenic sinusoids.
Spleen
Red Pulp has Splenic cords and Splenic Sinusoids: which are lined by unusual endothelial cells called
stave cells that are elongated and aligned parallel to the blood flow, with open slits between the cells.
Spleen
Blood flow in red pulp is either a closed circulation, moving from capillaries into the venous sinusoids, or
an open circulation, with capillaries opening directly into the splenic cords.
Spleen
Blood filtration in the open circulation involves interaction with splenic cord macrophages that remove….
old, swollen RBCs unable to slip between stave cells to reenter the venous blood flow.
Q Bank 1 - 3
- Which function is carried out by all lymphoid tissues and organs?
d. Production of lymphocytes - Which structure is partly encapsulated and covered by nonkeratinized stratified squamous epithelium?
c. Palatine tonsil - Which cell type gives rise to both memory and effector cells and is primarily associated with humoral immunity?
a. B lymphocyte
Q Bank 4 -6
- Recycling of iron and heme, the major complex containing iron, occurs most actively in which lymphoid organ(s)/tissue(s)?
d. Spleen - Which description is true of all secondary (peripheral) lymphoid organs?
e. Contain lymphoid nodules
- Which structure would be most heavily labeled by an immunohistochemical method targeting the CD8 surface antigen?
b. Paracortex
Q bank 7
- 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?
e. Conditions related to autoimmunity
Qbank 8
- 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?
c. Thymus
Q bank 9
- A 12-year-old African-American girl 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?
e. Splenic cords (of Billroth)
Q bank 10
- A 6-year-old boy is brought to the clinic where his mother reports that 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 painless 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?
b. Formation of germinal centers for B-cell proliferation in each node’s cortex
