3. OVERVIEW OF LYMPHOCYTE DEVELOPMENT
The maturation of B and T lymphocytes involves a series of
events that occur in the generative lymphoid organs. These
events include the following:
1. The commitment of progenitor cells to the B cell or T cell
lineage.
2. Proliferation of progenitors and immature committed cells at
specific early stages of development, providing a large pool of
cells that can generate useful lymphocytes.
3. The sequential and ordered rearrangement of antigen
receptor genes and the expression of antigen receptor proteins.
4. OVERVIEW OF LYMPHOCYTE DEVELOPMENT (cont.)
4. Selection events that preserve cells that have produced
correct antigen receptor proteins and eliminate potentially
dangerous cells that strongly recognize self antigens. These
checkpoints during development ensure that lymphocytes that
express functional receptors with useful specificities will mature
and enter the peripheral immune system.
5. Differentiation of B and T cells into functionally and
phenotypically distinct subpopulations. B cells develop into
follicular, marginal zone, and B-1 B cells, and T cells develop into
CD4+ and CD8+ T lymphocytes and γδ T cells. This
differentiation into distinct classes provides the specialization that
is an important characteristic of the adaptive immune system.
5. Development of B cells
B cells develop in the bone marrow and migrate to peripheral lymphoid organs,
where they can be activated by antigens.
6. Development of T cells
T cells undergo development in the thymus and migrate to the peripheral lymphoid
organs, where they are activated by foreign antigens.
21. Contributions of different mechanisms to the
generation of diversity in Ig and TCR genes
The rearrangement of antigen receptor genes is the key event in lymphocyte
development that is responsible for the generation of a diverse repertoire.
45. Antibody production
• Polyclonal antibodies - antisera
immunization
antibody purification
• Hybridomas and monoclonal antibodies
antibody designe and production
humanization
large scale fermentation
47. Characteristics of polyclonal
antibodies
• Blood serum (mixture of different antibodies
with altered isotype and idiotype and
affinity)
• Characterised by avidity
• Standard (during the bench)
50. Characteristics of monoclonal
antibodies
• Produced by genetic engineering
• Specific for single epitope exclusively
• Uniform antibodies with the same isotype and
idiotype
• Characterized by chemical affinity
• Standard by the continuous cell line
56. Antibodies for medical application
• Antibodies developed for therapeutic use
– Polyclonal antisera
– Monoclonal antibodies
• Antibodies for in vitro laboratory diagnostics
• Antibodies for in vivo diagnostic imaging
57.
58.
59.
60.
61. New production greenhouse facilities are also available to ………… through a
collaboration with the University of Arkansas at Fayetteville. These plant growth
facilities will support cGMP compliant growth of transgenic plants for the
expression of monoclonal antibodies in plants.
72. In the cases of local immune responses the
immune reaction develops in the place of the
antigen administration (in the external and/or
internal body surface) and remains locally.
Different connections are existing between the
systemic and local immunity.
External skin surface (“dry body
surface” is apr. 1.7 - 1.8 m2) and the
internal mucosal surface, (“wet body
surface” is apr. 400 m2).
75. Skin associated immune system (SIS or
SALT)
Special structural elements:
• Antigen presenting cells (Langerhans cells, veiled
cells, monocytes, tissue macrophages)
• Effector cells (gamma-delta T cells, alpha-beta T
cells, B cells, NK cells, granulocytes, mast cells),
• Keratinocytes (cytokine production).
The co-operation between keratinocytes and T cells
is similar to the thymus epithelia and thymocyte co-
operations.
90. Functions of immunoglobulins
Monofunctional character (specific antigen
recognition and binding) before the antigen
administration.
Polyfunctional character after the antigen
administration during the effector functions
(agglutination, precipitation, complement fixation,
opsonization, immunocomplex formation,
neutralisation, FcR binding, signal transduction).
Elimination of pathogens before an infection.
91. Immunoglobulin mediated basic mechanisms
against pathogens
1. Neutralisation: defence against
infections, blocking toxic molecules
2. Opsonisation: covering pathogens,
enhancing Fc receptor mediated
phagocytosis
3. Complement activation: C3b
opsonisation and bacteriolysis
4. Antibody Dependent Cell-mediated
Cytotoxicity (ADCC)
94. Antigen-antibody reactions
• neutralization of the antigen
• activation of the complement classical
pathway
• immunocomplex formation and activation
of the phagocytic functions
• antibody derived cell mediated cytotoxicity
(ADCC)
95. Neutralizing antibodies block bacterial adhesion
to host cells
IgA blocks adhesion to mucosal surface
Opsonisation with IgG increases the phagocytosis,
with IgG and/or IgM activates the complement causing lysis
Antibody-mediated agglutination blocks the penetration of pathogen
98. Antibodies neutralize viruses
Antibody inhibits adhesion of pathogen to the host cells blocking
infection:
-Influenza viruses adhere to the sialic acid residues of cell membrane
glycoproteins
-Rhinovirus adhere to the ICAM-1
-Epstein-Barr virus adhere to the complement receptor type 2
115. Model of CTL induced target cell apoptosis
Soluble effectors: perforins and granzymes
Membrane-bound effectors: Fas ligand (FAS-L)
CD95L
CD95
116. T cells
• 5 % of the T cells,
• Intraepidermal lymphocytes: CD4- and CD8-
• Intraepithelial lyphocytes: CD8+
• Produced in embryonic life, no recirculation,
• Limited, tissue specific TcR diversity specialization to respond
to certain antigens
• Ligand recognition: - non-MHC-retricted, but antigen specific
• Antigens: viral proteins, surface heat-shock proteins (produced in
inflammatory responses) bacterial lipids, phosphatids
• Function: eliminate damaged cells and microbial invaders
117. Natural killer cells (NK)
• 5-12% of lymphocytes = LGL cells
• TcR- CD3-, CD4-, CD8+/-, CD2+, CD16+
(FcRIII) CD56+,
• They secrete cytokines: INF immune
regulation (Th1)
• NK-cell receptors:
• Killer inhibitory receptors (KIR): recognize
normal self MHC-I molecules
• Killer activatory receptors (KAR): recognize
aberrant glycosylation on tumor or virus
infected cell surface
Function: early response
to infection with certain
viruses, intracellular bacteria
and tumor cells
123. Basic Immunology
Lecture 19th - 20th
Suppression of the immune response
Cellular and molecular mechanisms participate in
suppression of the immune response
124. Balance in the immune regulation
ACTIVATION SUPPRESSION
125. What is the suppression?
• Suppression is a general biological function.
• Immunosuppression is a reduction of the
activation or efficacy of the immune system.
• Some portions of the immune system itself
have immunosuppressive effects on other
parts of the immune system.
126. Regulators involved in the
suppression
• Antigen is the main regulator: withdraw the antigen
stop the Ig production and proliferation of T and B
lymphocytes
• Cytokine mediated T-cell regulation: Th1/Th2 balance
• APCs: T-cell co-stimulation – CD28/CTLA-4
• Regulatory T cells (natural and induced Treg)
• Antigen/immune complex: BcR+co-receptors
• Anti-idiotype antibody-mediated regulation
127. Basic regulation of the immune
response by cytokines
• General effects of cytokines: enhancing and
blocking of cell proliferation, migration, Ig
secretion, etc.
• Regulation of the CD4 T cell differentiation
(Th0, Th1, Th2, Th17) by the pattern of cytokines
The antigen-MHC-lymphokine regulations not
cover the total feedback mechanisms, other
pathways are necessary (network hypothesis).
128. Suppression in cellular level
• APC/macrophage suppression
• T cell suppression
• B cell suppression
129. APC/macrophage suppression
Activated macrophages produce different
inhibitory agents:
• large amount of incorporated thymidine from
the cells phagocyted and digested previously,
complement factors, polyamine oxidase
enzyme (PAO), interferon, cyclic AMP,
prostaglandins inhibit the proliferation.
• PD-1 (CD279) blocks the T cells (check point
inhibition)
130. T cell suppression
• Blocking through CTLA-4 (CD152) expressed by
activated T cells
• Th1 and Th2 cross regulations
• CD4/CD25+ regulatory T cells and other T-cell
subsets – NKT cells
• Different T cells functionally can suppress T and
B functions, but no specific Ts marker known
chemically!
137. Role of cytokines in the induction of
regulatory T cell (induced Treg)
iDC
iDC
DC1 DC2
Th1 Th2
Treg
Parasite,
allergen
LPS, virus RNA,
bacterial DNA
IL-12
IL-10 TGFβ
IL-4
INF
no
differentiation
IL-4IL-10 and TGFβ
Cellular immunity,
inflammation, IgG2
Humoral immunity
IgG1, IgE
Immunregulation,
Tolerance, IgA
iDC=immature DC
138. Thymus
CD4+CD8+
Periphery
Treg
CD4+ CD25+ CTLA-4+ FoxP3+
„natural” Treg
T naive
CD25-
Treg Teff
CD4+ CD25-CTLA-4+
FoxP3/-
induced Treg
effector T cell
Natural and induced regulatory T cell
(Treg) development
141. B cell suppression
• Antibody excess blocks the further activation
• Ig coated antigen inhibits the following B cell
activation through the low affinity FcγR II
(CD32) transmitted blocking signals (ITIM)
143. B cell inhibition by FcγRII (CD32)
• Antibody excess:
inhibition of B-cell
activation.
• Ig-coated antigen:
induces inhibition
via low-affinity
FcγR-II (ITIM)
receptors
Failure: autoimmune
diseases
144. Suppression by immunoglobulins
• The affinity maturation results in the formation of large amounts
of mutated immunoglobulins representing new structures
capable of inducing humoral immune response. The unique
antigenic determinants (idiotops) will elicit the generation of
antibodies against these structures within the V-regions of ag-
specific antibodies named “anti-idiotype antibodies”.
• Anti-isotype antibodies: the appearance of non-IgM (especially
IgG) isotype antibodies (so called „Rheuma factors”) will induce a
transient increase of antibodies against their constant regions
(IgM anti-IgG) contribute to the regulation of possible effector
mechanisms of humoral immune response.
147. Functions of the anti-idiotype network
• Suppression of B and T cells
• Functional memory formation
• Biological mimicry (insulin – anti-insulin – anti-
anti-insulin)
148.
149. • Suppression is a basic biological function.
• The whole immune machinery participate in the
suppressor functions, not a unique cell subset is
responsible for it.
• Several regulatory mechanisms are controlling
the immune response forming a regulatory
network which includes the suppression as a
basic immune function as well.
What is the suppression?