IMM2022 Study Guide - Final Guide: Innate Lymphoid Cell, Adaptive Immune System, Bone Marrow
12 May 2018
School
Department
Course
Professor
Glossary
Term
Definition
Innate immunity
Protection against infection that relies on mechanisms that exist before
infection, are capable of a rapid response to microbes, and react in
essentially the same way to repeated infections. The innate immune
system includes epithelial barriers, phagocytic cells (neutrophils,
macrophages), NK cells and other innate lymphoid cells, the complement
system, and cytokines, largely made by dendritic cells and mononuclear
phagocytes, that regulate and coordinate many activities of the cells of
innate immunity.
Adaptive immunity
The form of immunity that is mediated by lymphocytes and stimulated by
exposure to infectious agents. In contrast to innate immunity, adaptive
immunity is characterized by exquisite specificity for distinct macro-
molecules and by memory, which is the ability to respond more vigorously
to repeated exposure to the same microbe.
Haematopoietic
stem cell
An undifferentiated bone marrow cell that divides continuously and gives
rise to additional stem cells and cells of multiple different lineages. A
haematopoietic stem cell in the bone marrow will give rise to cells of the
lymphoid, myeloid, and erythrocytic lineage
Plasma
Component of blood (55% of blood volume) hold blood cells in suspension
Sera (serum)
The cell-free fluid that remains when blood or plasma forms a clot. Blood
antibodies are found in the serum fraction
Lymphoid lineage
Includes T cells, B cells and NKC
Myeloid lineage
Includes monocytes, macrophages, neutrophils, basophils, eosinophils,
erythrocytes, dendritic cells and platelets
Granulocyte
White blood cells with secretory granules in its cytoplasm eg an eosinophil
or basophil
Macrophage
A tissue based phagocyte that plays roles in innate and adaptive immune
responses. Macrophages are activated by microbial products sucj as
endotoxin and by T cell cytokines such as INF-y. activated macrophages
phagocytose and kill microorganisms, secrete pro-inflammatory cytokines
and present antigens to helper T cells.
Dendritic cell
Bone marrow derived cells found in epithelial and lymphoid tissues that
are morphologically characterised by thin membranous projections.
Classical dendritic cells function as innate sentinel cells and become APCs
for naïve T-cells upon activation of adaptive immune responses to protein
antigen.
Immature (resting) classical dendritic cells are important for induction of
tolerance to self-antigens.
Primary lymphoid
organs
Where lymphocytes are formed an mature
They provide an environment for stem cells to divide and mature into T
and B cells
Red bone marrow
The thymus
Secondary lymphoid
organs
(peripheral lymphoid organs)
Lymph nodes
The spleen
Maintain mature naïve lymphocytes and initiate an adaptive immune
response, the peripheral lymphoid are the sites of lymphocyte activation
by antigens
Activation leads to clonal expansion and affinity maturation
Lymphatics
A system of blood vessels throughout the body that collects the tissue
fluid called lymph, originally derived from the blood, and it returns
through the thoracic duct to the systemic circulation. Lymph nodes are
interspersed along these vessels and trap and retain antigens present in
the lymph.
Bone marrow
The tissue within the central cavity of bone that is the site of generation of
all circulating blood cells in adults, including immature lymphocytes, and
the site of B cell maturation
Thymus
A bilobed organ situated in the anterior mediastinum that is the site of
maturation of T cells from bone marrow derives precursor.
Primary lymphoid organ
Spleen
A secondary lymphoid organ
Major site of adaptive immunity responses to blood-borne antigens
The red pulp – active macrophages that ingest opsonized antigens and
damaged RBC
The white pulp – contains lymphocytes and lymphoid follicles where B
cells are activated
Mucosal immune
system
(MALT= mucosal
immunity)
Responds to microbes that enter the body through the mucosal surfaces
(GI tract, respiratory tract), also maintains tolerance to commensal
organisms that live on the outside of the mucosal epithelium
Composed of organizes mucosa associated lymphoid tissues, such as
peyers patches, as well as diffusely distributed cells within the lamina
propria
T cell zone
In the spleen
Peritubular lymphoid sheath
B cell zone
In the spleen
Follicle
Germinal centre
Specialised structures in lymphoid organs that develop during T-
dependent humoral immune responses, where extensive B cell
proliferation, isotype switching, somatic mutation, affinity maturation,
memory B cell generation, and induction of long-lived plasma cells take
place.
In lymphoid follicles in spleen, lymph nodes, and mucosal lymphoid tissue
Lymph node
Small, nodular, encapsulated lymphocyte-rich organs situated along
lymphatic channels throughout the body where adaptive immune
responses to lymph-borne antigens are initiated. Regulated the
interactions of B cells, T cells, DC and antigens to maximise the induction
of protective immune responses.
PAMPS
Pathogen associated molecular patterns
Structures produces by microorganisms but not mammalian (host) cells,
which are recognised by and stimulate the innate immune system. Eg
bacterial lipopolysaccharide and viral dsRNA
DAMPS
Danger associated molecular patterns
Endogenous molecules that are produces by or released from damages
and dying cells that bind to pattern recognition receptors and stimulate
innate immune responses
Eg extracellular ATP
TLRs
A family of pattern recognition receptors of the innate immune system
that are expressed on the surface and in endosomes of many cell types
and that recognise microbial structures, such as viral RNA, and transduce
signals that lead to the expression of inflammatory and antiviral genes
Lysosome
A membrane bound, acidic organelle abundant in phagocytic cells that
contains proteolytic enzymes that degrade proteins derived both from the
extracellular environment and from within the cell. Lysosomes are
involved and from within the cell. Lysosomes are involved in the class 2
MHC pathway of antigen processing
Phagosome
A membrane bound intracellular vesicle that contains microbes or
particulate material from the extracellular environment. Phagosomes are
formed during the process of phagocytosis. They fuse with other vesicular
structures such as lysosomes, leading to enzymatic degradation of the
ingested material
Phagolysosome
Is a cytoplasmic body formed by the fusion of a phagosome with a
lysosome in a process that occurs in phagocytosis
NK cells cytokines
Innate cells
Kill microbe0infected cells by direct lytic mechanisms and by secreting
IFN-y
Chemokines
Stimulate leukocyte chemotaxis, regulate the migration of leukocytes
from the blood to tissues by activating leukocyte integrins, and maintain
the spatial organization of different subsets of lymphocytes and APCs in
lymphoid organs
Il-2
Regulates activity of leukocytes
IL-4
Th0 Th2 cells
Integrin
Mediate adhesion of cells to other cells or to ECM
Important in T cell interactions with APCs
Migration of leukocytes from blood to tissues
LFA-1 and VLA-4 are integrins
Selectin
Mediate adhesion of leukocytes to endothelial cells
Complement system
Serum and cell surface proteins that interact with one another and with
other molecules of the immune system to generate important effectors of
innate and adaptive immune responses
Classical antigen-antibody complexes
Alternative microbial surfaces
Lectin plasma lectins binding to microbes
Generate inflammation and opsonins
All three lead to MAC complex
C3 convertase
Multiprotein enzyme complex in the complement activation. Cleaves C3
which gives rise to C3a and C3b
Membrane attack
complex
A lytic complex of the terminal components of the complement cascade
including multiple copies of C9, which forms in the membranes of target
cells. The MAC causes lethal ionic and osmotic changes in cells.
Affinity
The strength of binding between a single binding site on a molecule and a
ligand eg antibody to antigen
Avidity
Sum of affinity – overall strength of interaction between two molecules
such as antibodies and antigens
Humoral immunity
A type of adaptive immune response mediated by antibodies produced by
B lymphocytes
Principle defence mechanism against extracellular microbes and their
toxins
Antigen presenting
cells
A cell that displays peptide fragments of protein antigens, in association
with MHC molecules, on its surface and activated antigen-specific T cells.
Document Summary
Protection against infection that relies on mechanisms that exist before infection, are capable of a rapid response to microbes, and react in essentially the same way to repeated infections. The form of immunity that is mediated by lymphocytes and stimulated by exposure to infectious agents. In contrast to innate immunity, adaptive immunity is characterized by exquisite specificity for distinct macro- molecules and by memory, which is the ability to respond more vigorously to repeated exposure to the same microbe. An undifferentiated bone marrow cell that divides continuously and gives rise to additional stem cells and cells of multiple different lineages. A haematopoietic stem cell in the bone marrow will give rise to cells of the lymphoid, myeloid, and erythrocytic lineage. Component of blood (55% of blood volume) hold blood cells in suspension. The cell-free fluid that remains when blood or plasma forms a clot. Blood antibodies are found in the serum fraction.
