CHAPTER 5: THE IMMUNE RESPONSE SYSTEM (LYMPHOID SYSTEM) Flashcards
(111 cards)
1
Q
ORGANS OF IMMUNE RESPONSE: LYMPHOID SYSTEM
Divided into two:
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Primary and Secondary lymphoid organs
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Q
: Main producers of lymphocytes (B cells and T cells)
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Primary
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: Site of maturation and site where lymphocytes can perform their main functions.
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Secondary
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Q
Provide appropriate microenvironments or the development and maturation of lymphocytes
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PRIMARY LYMPHOID ORGANS
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Q
PRIMARY LYMPHOID ORGANS
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Bone marrow and thymus
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Q
Largest tissue of the body (adult: 1300 to 1500g)
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Bone Marrow
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Q
Primary source of pluripotent stem cells that give rise to all hematopoietic stem cells (HSC)
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Bone Marrow
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Q
Common myeloid progenitor gives rise to
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erythrocytes, platelets, basophil, eosinophil, and granulocytes
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Q
Common lymphoid progenitor gives rise to
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B and T cells
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Q
Major organ for B cell maturation (“B” cells = “B”one marrow) gives rise to the precursor cells of the
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thymic lymphocytes
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Q
Bone Marrow
Functions:
Produce large numbers of (?), each with unique (?) such that, overall, there is sufficient B cells diversity to recognize millions of microbial antigens in the environment.
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B cells
antigen receptors (antibodies)
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Q
Eliminate B cells with antigen receptors having
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high affinity for self-molecules
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Q
Bone Marrow Center for
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antigen-independent lymphopoiesis
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Q
B cells in bone marrow are
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naïve B cells
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Q
means there is no prior interaction with an antigen
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Naïve
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Maturity of B cells is not dependent of
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antigen interaction
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Q
= T cells (Most abundant)
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• 61-89%
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= NK cells
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• 22%
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= B cells
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• 10-20%
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Q
Flat bilobed organ above the heart
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Thymus
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Q
Thymus
Weighs and average of (?) at birth, reaches about (?) at puberty, and then gradually atrophies.
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30 g
35 g
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Q
Although the thymus diminishes in size, it is still capable of producing (?) until atleast the (?) of life.
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T lymphocytes
fifth or sixth decade
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Q
Thymus
Each Lobe surrounded by a (?) and divided into (?).
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capsule
lobules
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Q
Each lobule:
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Outer cortex
Inner medulla
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densely packed with immature T cells: thymocytes
Outer cortex
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immature T cells
thymocytes
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- lymphocyte precursors with acquired surface membrane antigens.
Thymocytes
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Thymocytes-
(?) are acquired as the (?) travel from the (?) over aperiod of (?).
Surface antigens
lymphocytes
cortex to the medulla
2 to 3 weeks
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: sparsely populated with thymocytes
Inner medulla
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Progenitors of T cells appear in the fetus as early as (?)
8 weeks in the gestational period
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Essential to acquisition of immunocompetence by the time the infant is born.
Progenitors of T cells
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Site of T-cell development and maturation through rearrangement of gene segments that encode (?)
T cell receptor
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Progenitor cells that migrate to the thymus proliferate and differentiate under the influence of the
humoral factor-thymosin
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Trap antigen from defined tissues or vascular spaces and are sites where mature lymphocytes can interact effectively with the antigen
SECONDARY LYMPHOID ORGANS
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SECONDARY LYMPHOID ORGANS
Tonsils, spleen (entry through circulation), lymph nodes (Lymphatics and skin), Peyer’s patches, appendix, and mucosa-associated lymphoid tissue (MALT).
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potential sites for contact with foreign antigen
SECONDARY LYMPHOID ORGANS
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increase the probability of an immune response
SECONDARY LYMPHOID ORGANS
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are located along lymphatic ducts
Lymph nodes
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serve as central collecting points for lymph fluid from adjacent tissues
Lymph nodes
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arises from passage of fluids and low molecular- weight solutes out of blood vessel walls and into the interstitial spaces between cell
Lymph fluid
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Some of this interstitial fluid returns to the bloodstream through (?), but a portion flow through the (?) and is eventually collected in thin-walled vessels known as (?)
venules
tissues
lymphatic vessels
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are especially numerous near joints and where the arms and legs join the body
Lymph nodes
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Nodes range in size from (?) to about (?) in diameter
1 mm
25 mm
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Filtration is a main function of these organs.
Lymph Nodes
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The lymph fluid flows slowly through spaces called (?), which are lined with (?), creating an ideal location for phagocytosis to take place.
sinuses
macrophages
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Lymph Nodes
The tissue is organized into an (?).
outer cortex, a paracortex, and an inner medulla
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Layers of Lymph Node
Cortex
Paracortex
Inner Medulla
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Lymph Node Cells:
Macrophages, most of B cells, follicular dendritic cells
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The outermost layer
Cortex
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Contains macrophages and aggregations of B cells (Mature resting/Naïve) in primary follicles similar to those found in the spleen.
Primary Follicles
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Specialized cells called follicular dendritic cells are also located here.
Primary Follicles
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Found only in lymphoid follicles
follicular dendritic cells
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have long cytoplasmic processes that radiate out like tentacles
follicular dendritic cells
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These cells exhibit a large number of receptors for antibody and complement
follicular dendritic cells
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help to capture antigen to present to T and B cells
follicular dendritic cells
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Consist of antigen-stimulated proliferating B cells.
Secondary Follicles
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The interior of a secondary follicle is known as the (?), because it is here that (?) of the B cells takes place.
germinal center
blast transformation
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→ B cell will further develop to plasma cells which will produce memory T cell
Blast transformation
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which actively secrete antibody
Plasma cells
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which are just a step away from forming plasma cells
memory cells
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Secondary Follicles
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Primary Follicles
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Paracortex Cells:
Most T cells
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Space between cortex/follicles and medulla
Paracortex
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are mainly localized in the paracortex
T lymphocytes
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T lymphocytes are in close proximity to antigen-presenting cells called
interdigitating cells
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Inner Medulla Cells:
mostly macrophages, numerous plasma cells
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The medulla is less densely populated but contains some (?)
T cells (in addition to B cells), macrophages, and numerous plasma cells
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(?) are removed as the fluid travels across the node from (?). The transit time through a lymph node is approximately (?)
Particulate antigens
cortex to medulla
18 hours
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If contact with antigen takes place, lymphocyte traffic shuts down due to the proliferation of activated cells.
Inner Medulla
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Accumulation of lymphocytes and other cells causes the lymph nodes to become enlarged, a condition known as lymphadenopathy.
Inner Medulla
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Recirculation of expanded numbers of lymphocytes then occurs
Inner Medulla
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Largest secondary lymphoid organ
Spleen
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Spleen
having a length of approximately (?) and weighing (?) in the adult
12 cm
150 g
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It is located in the upper-left quadrant of the abdomen, just below the diaphragm and surrounded by a thin connective tissue capsule.
Spleen
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The organ can be characterized as a large discriminating filter
Spleen
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removes old and damaged cells and foreign antigens from the blood
Spleen
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Each day, an adult’s blood volume passes through the spleen approximately (?)
four (4) times
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can constantly survey for infectious agents or other foreign matter
lymphocytes and macrophages
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Splenectomy: Increases risk of infection with
encapsulated bacteria and severe malaria
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Splenic tissue can be divided into two main types:
red pulp and white pulp
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Red Pulp Cells:
Platelets, RBCs, WBCs
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Makes up more than one-half of the total volume
Red Pulp
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Its function is to destroy old red blood cells through splenic culling.
Red Pulp
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Blood flows from the arterioles into the red pulp and then exits by way of the splenic vein
Red Pulp
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Comprises approximately 20 percent of the total weight of the spleen and contains the lymphoid tissue, which is arranged around arterioles in a periarteriolar lymphoid sheath
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Lymphocytes enter and leave this area by means of the many capillary branches that connect to the arterioles.
White Pulp
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This sheath contains mainly T cells.
PALS
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Attached to the sheath are primary follicles, which contain B cells that are not yet stimulated by antigen.
Follicular Area
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Surrounding the PALS ; containing dendritic cells that trap antigen.
Marginal Zone
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Marginal Zones
MACs, CD4 T cells (T helper cells), B cells
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50% of lymphoid tissue in human body is located in the lining/mucosa of major tracts
Mucosal Associated Lymphoid Tissue (MALT)
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found in the gastrointestinal, respiratory, and urogenital tracts
Mucosal Associated Lymphoid Tissue (MALT)
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Here macrophages and lymphocytes are localized at some of the main ports of entry for foreign organisms.
Mucosal Associated Lymphoid Tissue (MALT)
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(?) represent a specialized type of MALT and are located at the (?) of the intestinal tract.
Peyer’s patches
lower ileum
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Types of MALT
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Nasal
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throat and nasal passages: and, tonsils
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Gut; Peyer’s patches:
GALT
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specialized epithelium antigen presenting cells and intraepithelial lymphocytes.
GALT
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Liver
GALT
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Features immunoglobulin A (IgA) production and involves a unique pattern of lymphocyte recirculation.
GALT
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Important for the development of tolerance to ingested antigen
GALT
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Bronchus
BALT
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lymphoid aggregates and follicles along main bronchi
BALT
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It is mainly associated with IgA production in response to inhaled antigens
BALT
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The epidermis contains a number of intraepidermal lymphocytes.
Cutaneous Associated Lymphoid Tissue (CALT)
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Most of these are T cells, which are uniquely positioned to combat any antigens that enter through the skin.
Cutaneous Associated Lymphoid Tissue (CALT)
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This association of lymphocytes is known as the cutaneousassociated lymphoid tissue.
Cutaneous Associated Lymphoid Tissue (CALT)
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Found in the mucous membrane lining of the oral and pharyngeal cavities
Tonsils and Appendix
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Function: to respond to pathogens entering the respiratory and alimentary tracts
Tonsils and Appendix
