Approval Sheet CD4+ T cell affinity in autoimmunity and viral infection 公开
Sabatino Jr., Joseph (2010)
Abstract
CD4+ T cell affinity in autoimmunity and viral infection
By Joseph J. Sabatino, Jr.
Cellular immunity is mediated by engagement of the T
cell receptor (TCR) with specific
peptide:MHC (pMHC) antigen leading to the induction of T cell
effector functions. The
affinity of the TCR for antigen is believed to be a critical
determinant for antigen-
specificity. The existing models of clonal selection and affinity
maturation posit that the
highest affinity T cells dominate in a polyclonal T cell response.
However, the minimal
affinity required for T cell activation is unknown, therefore it is
unclear to what extent
low affinity T cells contribute to polyclonal T cell responses.
Moreover, although it is
postulated that T cells specific for self- and foreign-antigens
differ in their respective
affinities due to tolerance, it is unclear whether this is in fact
the case. The answers to
these vital questions have been hindered by the lack of sensitive
techniques for the
measure of individual T cells that comprise a polyclonal
antigen-specific T cell
population. Using a highly sensitive two-dimensional (2D) binding
assay, the affinities
of CD4+ T cells specific for central nervous system (CNS)-derived
antigen and a viral-
antigen were compared. These studies revealed that the autoreactive
CD4+ T cells were
overall of lower affinity than those specific for viral-antigen,
underlying their differences
in detection by pMHC II tetramers. Remarkably, the majority of CD4+
T cells in CNS
autoimmune disease were cross-reactive for myelin- and
neuronal-antigens, yet were
primarily of low affinity. However, an extensive degree of T cell
affinity diversity was
observed in all polyclonal CD4+ T cell responses, suggesting that a
range of low to high
antigen-specific T cells is a hallmark of cellular immunity. These
findings indicate that
polyclonal CD4+ T cell responses are larger than previously
believed and challenge the
existing paradigms of T cell affinity in immunity. T cell affinity
may therefore play a
crucial role in the initiation, duration, and modulation of
polyclonal T cell responses,
which may critically alter the outcome and treatment of
autoimmunity and infection.
Table of Contents
Table of Contents
Chapter 1
:
Introduction……………………………………………………………….1-25
Figure 1.1: Alteration of TCR or MHC contact residues distinguishes
altered peptide
ligands and MHC variant
peptides…………………………………...…………………..26
Figure 1.2: MOG35-55-induced EAE disease
course……………………………...............27
Table 1.1: Comparison of TCR:pMHC kinetics to other
receptor-ligand
interactions……………………………………………………………………………….28
Table 1.2: Summary of commonly used EAE
models…………………………………...29
Table 1.3: Summary of altered peptide ligand therapies in
EAE………………………..30
Table 1.4: Summary of MHC variant peptide therapies in
EAE………………...............31
Chapter 2: Loss of IFNγ enables the expansion of
autoreactive CD4+ T cells to induce
EAE by a non-encephalitogenic myelin variant
antigen……………………………..32-49
Figure 2.1: IFNγ -/- and IFNγR -/- mice develop
significant EAE following 45D
immunization…………………………………………………………………………….50
Figure 2.2: 45D induces significant lymphocyte infiltration in the
CNS of IFNγ -/- and
IFNγR -/-
mice…………………………………………………………………………...51
Figure 2.3: MOG tetramer-positive CD4+ T cells are found in the CNS
of 45D-
immunized IFNγ -/- and IFNγR -/-
mice………………………………………………...52
Figure 2.4: Splenocytes from 45D-immunized IFNγ -/- and
IFNγR -/- mice proliferate
significantly in response to MOG
35-55…………………………………………………53
Figure 2.5: Loss of IFNγ increases absolute numbers of
MOG:I-Ab tetramer positive
CD4+ T cells in the
periphery…………………………………………………………....54
Figure 2.6: CD4+ T cells from 45D-immunized IFNγ -/- and
IFNγR -/- mice do not
demonstrate an enhanced IL-17-secreting
phenotype…………………………………...55
Table 2.1: EAE incidence, average severity and day of onset in
wild-type, IFNγ -/- and
IFNγR -/- mice immunized with MOG or
45D………………………………………….56
Chapter 3: High prevalence of low affinity peptide:MHC II
tetramer-negative effectors
during polyclonal CD4+ T cell
responses……………………………………………57-70
Figure 3.1: Tetramer versus 2D detection of polyclonal MOG35-55 and
GP61-80 CD4+ T
cells…………………………………………………………………………………...71-72
Figure 3.2: TCR levels of MOG35-55 and GP61-80 CD4+ T
cells…………………………73
Figure 3.3: Kinetics of maximal adhesion frequency ( Pa) of
polyclonal CD4+ T
cells………………………………………………………………………………………74
Figure 3.4: 2D affinity and antigen-specificity of
tetramer-positive and tetramer-negative
CD4+ T
cells………………………………………………………………………….75-76
Figure 3.5: Sorting of CD4+ T cells by tetramer
binding………………..........................77
Figure 3.6: Dominance of pro-inflammatory low affinity
myelin-reactive CD4+ T cells
during
EAE………………………………………………………………………………78
Figure 3.7: Low affinity viral-specific CD4+ T cells contribute
significant effector
responses during LCMV
infection……………………………………………………….79
Chapter 4: Low affinity cross-reactive myelin- and
neuronal-antigen-specific CD4+ T
cells predominate during CNS
autoimmunity………………………………………..80-96
Figure 4.1: Functional cross-reactivity of 2D2 TCR transgenic and
polyclonal CD4+ T
cells………………………………………………………………………………………97
Figure 4.2: pMHC II tetramer detection of MOG35-55 and
NF-M15-35-specific CD4+ T
cells……………………………………………………………………………………....98
Figure 4.3: MOG and NF-M tetramer co-staining of polyclonal CD4+
T
cells………………………………………………………………………………………99
Figure 4.4: 2D binding analysis of 2D2 and polyclonal MOG35-55 and
NF-M15-35 CD4+ T
cells……………………………………………………………………………………..100
Figure 4.5: pMHC II tetramer and functional reactivity of MOG35-55
and NF-M15-35 CD4+
T cells in the CNS during
EAE…………………………………………………………101
Figure 4.6: High frequency of low affinity MOG and NF-M
cross-reactive CD4+ T cells
in the CNS during peak
EAE…………………………………………………………...102
Figure 4.7: Effect of sequential MOG:IAb and NF-M:IAb binding on
the adhesion
frequency of CD4+ T
cells…………………………………………………...................103
Figure 4.8: Stimulation of MOG35-55 CD4+ T cells in vitro
increases cross-reactivity to
NF-M…………………………………………………………………………………...104
Chapter 5:
Discussion…………………………………………………………….105-115
Figure 5.1: Proposed model of the consequences of polyclonal T cell
affinity diversity in
polyclonal immune
responses…………………………………………………………..116
References…………………………………………………………………………117-139
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