Immune System and Lymphoid Tissue Flashcards
It is more of a functional system ; provides defense or immunity against infectious agents ranging from viruses to multicellular parasites
Immune System
Immune System is composed of various cells called?
White Blood Cells and Antigen Presenting Cells
Where does cells in the Immune System usually concentrate?
Lymphoid Organs
2 divisions of Immune System
- Innate Immunity
- Adaptive Immunity
It is the pre-existing nonspecific defenses
Innate Immunity
Innate Immunity is composed of:
- Physical barriers
- Chemical defenses
- Various secretory substances
- Phagocytes
The main effector of our innate immune system
Phagocytes
Acquired gradually by exposure to microorganisms, is more specific, slower to respond
Adaptive Immunity
determines the microbe or invader and then presents it to the lymphocytes to mount a more specific attack
Antigen Presenting Cells (APCs)
involves the cytotoxic elimination, via the CD8 or the cytotoxic lymphocyte
Cellular response
this molecule is recognized by cells of the adaptive immune system and typically elicits a response from these cells
Antigen
It is an antigenic determinants
Epitopes
It is secreted by plasma cells
Antigen
These are able to bind specifically and neutralize certain viral particles and bacterial toxins
Antibodies
Antibodies are also known as:
Immunoglobulins
Five major classes of immonoglobulins
IgG, IgA, IgM, IgE and IgD
What does the bodies triggers in vaccination
Antibodies
The bonding of Fc portion promotes
Complement activation
Opsonization
NK (natural killer) cell activation
Facilitates the enhanced phagocytosis
Opsonization
What does the binding of antigen-binding site of an antibody with antigen causes?
Neutralization
Agglutination
Precipitation
Antibody covers biologically active portion of microbe or toxin
Neutralization
Antibody cross-links cells, such as bacteria, forming a “clump”
Agglutination
Antibody cross-links circulating particles, such as toxins, forming and insoluble antigen-antibody complex
Precipitation
group of molecules that attacks the membrane of a microbe and cause cell lysis
Complement fixation
antibodies coats the bacterium and make it more appealing to the phagocytes for eating
Opsonization
releases perforin and granzymes
NK Cells
substances that creates holes unto
bacterium, but most likely into virus-infected cells
perforin and granzymes
Cells of Adaptive Immunity
Antigen and Lymphocytes
Lymphocytes aredivid ed into:
B lymphocytes and T lymphocytes
T lymphocyte is further subdivided into:
Helper T Cells and Cytotoxic T Cells
These cells are denoted by the presence of the
CD4 protein ; assist in the immune responses by
producing cytokines that promote the differentiation of our B cells unto plasma cells ; activate macrophages to become phagocytic ; activate cytotoxic T lymphocytes
Helper T Cells
These cells are denoted by the presence of
CD8 protein ; represents what is called the cell
mediated immunity ; they directly attack tumor
cells
Cytotoxic T Cells
These cells has neither CD4 or CD8 ; more
on the inhibition of the specific immune
responses ; monitoring peripheral tolerance
Regulatory T Cells
important in the development of the T
lymphocytes in the thymus
Regulatory T Cells
groups of cells, tissues, and organs that monitor body surfaces and internal fluid compartments and
react to the presence of potentially harmful
substances
Lymphoid Organs
The definitive cell type
Lymphocytes
Lymphoid organs are divided into:
Primary Lymphoid Organs
Secondary Lymphoid Organs
Lymphoid organs are divided into:
Primary Lymphoid Organs
Secondary Lymphoid Organs
Thymus and Bone Marrow
Primary Lymphoid Organs
Lymph nodes, Spleen and Diffuse lymphoid tissue
Secondary Lymphoid Organs
It is usually what is called the gastric associated lymphoid tissue (GALT), found in the digestive tract
Diffuse lymphoid tissue
lymphoid tissue found in the pulmonary tract
Bronchi associated lymphoid tissue
primary or central lymphoid organ in which T cells
are produced
Thymus
bilobed structure in the mediastinum of the
sternum ; originates from the embryo’s third pair of
pharyngeal pouches
Thymus
Its main function is the induction of central tolerance
Thymus
It is when the thymus shrinks as the person ages
Involution
Outer portion of the parenchyma ; Darkly basophilic ; Contains an extensive population of T
lymphoblasts
Cortex
it refers to young lymphocytes
Thymocytes
an active thymus is packed with small, highly basophilic lymphoblasts that proliferate as well as undergo positive and negative selection in that region
Cortical Zone
It has something to do with acquiring CD4 or CD8 receptor
Positive and negative selection
there is also the elimination of T cells that would react to self-antigen ; if they react to self-antigen, they will be induced to undergo apoptosis
Positive and negative selection
Meshwork of unusual thymic epithelial cells that supports lymphoblast in the cortical zone
Cytoreticulum
Inner portion of the parenchyma ; Contains mostly large lymphocytes ; Thymic or Hassall’s corpuscles
Medulla
considered to be the potent source of the cytokine which is necessary for the differentiation and maturation of the T lymphocytes
Hassall’s corpuscles
They provide a framework for the developing T
cells
Epithelioreticular cells
6 types of epithelioreticular cells
Type I, II, III, IV, V, and VI
function as a barrier that isolates developing T cells from the connective tissue of the organ
Type I
express MHC I and MHC II molecules,
which are involved in thymic cell education
Type II
functional barrier; possess MHC I
and MHC II molecules
Type III
with type III cells, they create the
barrier at the corticomedullary junction (the
separation between the cortex and medulla)
Type IV
provide the cellular framework of the
medulla and to compartmentalize groups of
lymphocytes
Type V
form the most characteristic feature of the thymic medulla, the thymic (Hassall’s) corpuscles
Type IV
this protects the developing lymphocytes in the thymus from the exposure to antigens
Blood-Thymus Barrier
has an efferent lymph vessel but no
afferent
Blood-Thymus Barrier
mucosa-associated lymphatic tissue (MALT)
Diffuse Lymphatic Tissue
Discrete concentrations of lymphocytes
contained in a meshwork of reticular cells
Lymphatic nodules
Where does most of the lymphocytes activate with the use of antigen presentation which includes MALT, lymph nodes and spleen
Lymphatic nodules
lymphatic nodule consisting
chiefly of small lymphocytes
Primary Nodule
It has germinal center
Secondary Nodule
contains large immature lymphocytes (lymphoblasts and plasmablasts) ; a morphologic indication of
lymphatic tissue response to antigen
Germinal Center
Large, irregular masses of lymphoid tissue in
the mucosa of the posterior oral cavity and
nasopharynx where their cells encounter
antigens entering the mouth and nose
Tonsils
deep invaginations in which
the epithelial lining is densely infiltrated with
lymphocytes and other leukocytes
Tonsillar Crypts
3 Types of Tonsils
Palatine
Lingual
Pharyngeal Tonsils
continuous with esophagus;
stratified squamous epithelium
Palatine
near the oral cavity ; covered by
stratified squamous epithelium ; lack distinct
capsules
Lingual
near the oropharynx ; pseudostratified ciliated columnar epithelium ; has a thin underlying capsule, lacks crypts
Pharyngeal Tonsils
Located in the ileum (large intestine) ; Consist of numerous aggregations of lymphatic nodules containing T and B lymphocytes
Peyer patches
A short, small diameter projection from the
cecum ; Lamina propria is heavily infiltrated with
lymphocytes and contains numerous
lymphatic nodules
Vermiform appendix
bean-shaped, encapsulated structures
distributed throughout the body along the lymphatic
vessels
Lymph Nodes
constitute a series of in-line filters of lymph
that defend against the spread of microorganisms
and tumor cells
Lymph Nodes
It is present within lymphoid nodules
FDCs (follicular dendritic cells)
most abundant cells of lymph nodes
lymphocytes of all types, plasma cells, dendritic
cells, macrophages, and other APCs (antigen
presenting cells)
Two types of lymphatic vessels serve the lymph
node
Afferent Lymphatic Vessels
Efferent Lymphatic Vessels
Convey lymph toward the node and enter it at
various points on the convex surface of the
capsule
Afferent Lymphatic Vessels
Convey lymph away from the node and leave
at the hilum
Efferent Lymphatic Vessels
Composed of dense connective tissue that
surrounds the node
Capsule
Also composed of dense connective tissue,
which extend from the capsule into the
substance of the node, forming a gross
framework
Trabeculae
Composed of reticular cells and reticular fibers that form a fine supporting meshwork throughout the remainder of the organ ; Dominates the lymph node
Reticular tissue
Forms the outer portion of the node except at
the hilum
Cortex
Components of Cortex
Subcapsular Sinus
Lymphoid Nodules
Receives lymph from the afferent lymphatics ; Lined by a very thin, discontinuous endothelium penetrated by reticulin fibers and processes of dendritic cells
Subcapsular Sinus
Spherical or oval aggregates of lymphocytes ; Formed largely by helper T lymphocyte and proliferating B lymphoblasts
Lymphoid Nodules
Without germinal center
Primary Nodule
With germinal center
Secondary Nodule
the sites within the lymph nodes where the mature B cells would proliferate, differentiate, and mutate their antibody genes
Germinal centers
Inner part of the lymph node
Medulla
Components of medulla
Medullary Cords
Medullary Sinuses
Branched cordlike masses of lymphoid tissue
extending from the paracortex ; Contain T and B lymphocytes and many
plasma cells
Medullary Cords
Dilated spaces lined by discontinuous
endothelium that separate the medullary
cords
Medullary Sinuses
about the size of a clenched fist ; largest lymphatic organ ; located in the upper left quadrant of the
abdominal cavity and has a rich blood supply
Spleen
only lymphoid organ involved in filtration of blood ; main site of old erythrocyte destruction ; a production site of antibodies and activated
lymphocytes
Spleen
restricted to the smaller areas;
usually surrounding the central arterioles
White Pulp
occupies most of the parenchyma
Red Pulp
Consists of a thick accumulation of
lymphocytes surrounding an artery
White Pulp
branch of the splenic artery
Central artery
compose of lymphocytes that aggregate
around the central artery
Periarterial lymphatic sheath (PALS)
Contains large numbers of red blood cells that
it filters and degrades
Red Pulp
Components of Red Pulp
Splenic Cords (of Billroth)
Splenic Sinusoids
Separated by the sinusoids ; Reticular tissue rich in macrophages and
lymphocytes
Splenic Cords (of Billroth)
Allows RBC to pass through if it still has its usual
discord shape
Splenic Sinusoids
elongated endothelial cells lining these
sinusoids, oriented parallel to the blood flow
and sparsely wrapped in reticular fibers and
highly discontinuous basal lamina
Stave Cells
