Transcript Document

Cellular and Molecular Immunology:
Peripheral B and T cell differentiation
Christoph Mueller; Institute of Pathology
[email protected]
• General principles:
- functional subsets
- plasticity vs. stability of phenotype
• Molecular basis of lymphocyte differentiation:
transcription factors
• Soluble factors and cognate interactions involved in
the differentiation of lymphoid cells
• Experimental approaches to study B/T cell differentiation
• Consequences of impaired T and B cell differentiation
RAG-1, 2
•
RAG1 and RAG2 (“Recombination Activation Genes”)
are essential for the rearrangement of the Ig and TCR
genes
•
Mice deficient for either RAG1 and/or RAG2 are
deficient for both T and B cells (but may still have some
NK cells)
•
to prevent the later generation of autoreactive T and B
cells, the expression of these two genes needs to be
tightly regulated
Regulation of T cell receptor gene rearrangement
Experimental approach for determining
the regulation of RAG gene expression
Experimental set-up
Mouse, transgenic for TCRab, recognizing the LCMV peptide
gp33 in the context of H-2 Db
- In a C57BL/6 (H-2b) genetic background: positive selection of
TCRab tg T cells, tg TCRab expressed on thymocytes)
- In a BALB/c (H-2d) background (no positive selection of TCRab
tg T cells; no tg TCRab expressed on thymocytes)
Working hypothesis: recognition of a MHC/Ag complex via a positively selecting
TCRab down-regulates RAG expression in the differentiating T cells, and thus,
terminates TCRab rearrangements
Cortex
Medulla
In situ hybridisation for the detection of RAG-1 mRNA
Thymus, wild type mouse (C57Bl/6 mouse)
Medulla
Cortex
Murine Thymus, TCRab tg mouse with a positively selecting
MHC haplotype: transcription of RAG1 gene is suppressed
Cortex
Medulla
Murine Thymus, TCRab tg mouse with a non - selecting MHC
haplotype: transcription of RAG1 gene is still active in the cortex
CD8 T cell differentiation
Functional Heterogeneity of
CD4 T Lymphocytes
naive CD4 T Cell
Th1
Th0
ThO: IL2, IL3, IL4, IL5, IL6, IL9, IL10, IFN
Th1: IL2, IFN , TNFalymphotoxin
Th2: IL4, IL5, IL6, IL9, IL10
Th2
Naïve
CD4
IL 4
IL 12
IFN 
Th 2
Th 1
Grogan & Locksley Curr Opinion Immunol 14: 366-72; 2002
Leprosy
• Chronic - progressive infectious disease, affecting the
skin, peripheral nerves and occasionally the respiratory
tract
• Infectious agent: Mycobacterium leprae
• Globally, approx. 10-20 million patients infected,
endemic in tropical areas (e.g. Southeast Asia; India,
South America, Subsaharan Africa)
Leprosy: Prevalence
Leprosy:
different clinical forms of the disease
Lepromatous Leprosy:
• Multiple, nodular lesions of the skin, in particular, of the
face (”lion face").
• Persistent bacteriemia, foamy cell-like lesions with
numerous M. leprae present
Tuberculoid Leprosy:
• Singular, small macular lesions of the skin.
• Peripheral nerves (e.g. N. ulnaris, peronealis, N.
auricularis) are often affected
sensory neuropathy.
• Granuloma are frequent (with only low numbers of
M. leprae present)
Immunological Spectrum of Leprosy
naïve CD4 T cells
Th1
Th0
Th2
cellular
immunity
humoral
immunity
Tuberculoid leprosy
Lepromatous leprosy
Granuloma formation
Persistence of M. leprae
Tissue damage may ensue
Disfiguring disorder
Lepromatous
leprosy
Tuberkuloid
leprosy
Type IV Hypersensitivity reactions
Fig. 5-11
Kumar 6th edition
Pathogens may influence the resulting adaptive immune response
Science 302: 993-4; 2003
Figure 1 Stimulating the Th1 or Th2 response. In both pathways, dendritic cells internalize the
pathogen. They present its antigens to T cells, which recognize antigens through their T-cell receptors
(TCR). a, Organisms such as intracellular bacteria or viruses are recognized by the Toll-like
receptors on dendritic cells; the resulting signals induce the secretion of interleukin-12 (IL-12) and
differentiation of CD4 T cells into the Th1 lineage that produces gamma interferon (IFN-). b, How
dendritic cells recognize larger pathogens, such as parasitic worms, is not known. But the end result
is differentiation of Th2 effector cells regulated by T-cell-produced interleukin-4 (IL-4).
Information1, 2 on the link between dendritic cells and T cells suggests that the former express
different Notch ligands — Delta or Jagged — under different conditions. Jagged is specifically
induced by stimuli known to induce Th2 differentiation. Notch signals (Notch-IC) can induce
transcription of IL-4 through direct binding of RBPJ to the IL-4 promoter1
Nature 430, 150 - 151 (08 July 2004)
# Publications per Year (PubMed)
Publications on Suppressor T cells and
Regulatory T cells
300
Suppressor T cells
250
Regulatory T cells
200
150
100
50
0
Rregulatory T cell subsets
Natural regulatory T cells express the cell-surface marker CD25 and the
transcriptional repressor FOXP3 (forkhead box P3). These cells mature and migrate
from the thymus and constitute 5–10% of peripheral T cells in normal mice. Other
populations of antigen-specific regulatory T cells can be induced from naive
CD4+CD25- or CD8+CD25- T cells in the periphery under the influence of semimature dendritic cells, interleukin-10 (IL-10), transforming growth factor- (TGF-) and
possibly interferon- (IFN-). The inducible populations of regulatory T cells include
distinct subtypes of CD4+ T cell: T regulatory 1 (TR1) cells, which secrete high levels
of IL-10, no IL-4 and no or low levels of IFN-; and T helper 3 (TH3) cells, which
secrete high levels of TGF-. Although CD8+ T cells are normally associated with
cytotoxic T-lymphocyte function and IFN- production, these cells or a subtype of
these cells can secrete IL-10 and have been called CD8+ regulatory T cells.
Mechanism(s) of suppression.
Various molecular and cellular
events have been described to
explain how Treg can suppress
immune responses. They
include: IL-2 gene expression
inhibition, modulation of
costimulatory molecules on APCs
and interaction of LAG3 with
MHC class II molecules (a),
immunosuppressive cytokine
secretion (b), induction of
tryptophan catabolism through
CTLA-4 (c) and cytotoxicity (d).
However, none of those
mechanisms can explain all
aspects of suppression. It is
probable that various
combinations of several
mechanisms are operating,
depending on the milieu and the
type of immune responses. It is
also possible that there might be
a single key mechanism that has
not been found yet (e).
Abbreviations: APC, antigen
presenting cell; TCR, T cell
receptor.
CD4 T cell differentiation (for beginners)
CD4 T cell differentiation (for specialists)
(Keiji Hirota, Bruno Martin and Marc Veldhoen, 2010):
B cells ….
CD4 T-Zelle
CD40L
2.Signal:
Quervernetzung der
Ig durch Antigen oder
Aktivierung durch CD40L
T-Zell-Hilfe
durch Zytokine
CD40
1. Signal:
Bindung des Antigen
an Ig
2. Signal
kein
2. Signal
naive B - Zelle
B-Gedächtniszelle
a
B-Zellen (CD19)
b
Mantelzone
T-Zellen (CD3)
c
d
„dark zone“
„light zone“
FDZ
(CD21)
e
Mantelzone
proliferierende Zellen
(Ki-67)
f
Keimzentrum
Mantelzone
Plasmazellen k l
Makrophagen
(CD68)
Keimzentrum
Program of my next lectures:
•
Molecular mechanisms of immune tolerance
•
Central tolerance induction in the B cell and T cell
compartment
•
Immune tolerance in the periphery
•
Immunopathology vs. Autoimmunity
•
Immune tolerance vs. Immune privilege vs. Immune
ignorance