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