IMM 334 IMM 335

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IMM 334 / IMM 335 Lecture Outlines M. Julius
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IMMUNOLOGY 334/335
Julius Lecture I (i) Lymphocyte production
homeostasis (ii) Immunoglobulin allotype
congenics do "T" or "B" cells make
antibody? (iii) The Clonal Selection Theory
versus Instructionalism -antigen receptor
expression -clonal distribution of antigen
receptors -precursor product relationship (iv)
"Affinity maturation" of the humoral immune
response -cross reactivity -activation
threshold/receptor occupancy -effect of antigen
concentration Ag -somatic
mutation (v) Antigen recognition by T
cells -the role of Antigen Presenting Cells
(APC) -activation of antigen specific precursor
"t" gives rise to effector "T" -cytotoxic or
"killer" T cells.....an assay for
death (vi) MHC restricted T cell
function -the generic experiment........."self"
antigen -"self" MHC.........another
congenic experiment
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Julius Lecture II (i) Characterization of MHC
restricted function -isolation of Ag/MHC
specific T cells......."The Pan" -the "F1"
experiment clonal distribution of T cell
receptor (TcR) (ii) Mapping of T cell
specificity -a closer look at the
MHC -recombinant inbred strains (iii) Alloreact
ivity -the problem of graft rejection -T
cells versus B cells -T cell cross
reactivity H-2dx H-2by (iv) Selection of
the T cell Repertoire -schematic notation for
T cell development and selection (v) The
Radiation Chimera -definition and
construction -P1?F1 chimera Balb/c ?(Balb/c x
C57Bl/6)F1 H-2d ?H-2d/b -negative
selection of "anti-self" T cells -positive
selection of the "self-restricted" T cell
repertoire (this discussion incorporates a
"white lie" which we shall reconsider) -clonal
distribution of T cell restriction specificities
in the P1?F1 chimera derived from a "Pan"
experiment
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Julius Lecture III (i) F1?P1Chimera (Balb/c x
C57Bl/6)F1?Balb/c H-2d/b?H-2d -loss of
restriction specificity -the thymic epithelium
is required for "positive" selection -MHC
expressed by stem cells can mediate "negative"
selection (ii) Role of the Thymic Epithelium
in Positive Selection -thymectomized recipients
for the production of "athymic" radiation
chimeras -"ectopic" thymus grafts versus
"orthotopic" thymus (iii) The Role of APC in the
Periphery selection versus expansion -return
to the P1?F1 chimera and the use of a virus as
antigen -rescue of P2 restricted T cell
function requires P2 expressing APC in the
periphery (iv) Immune Response (IR) Genes
"holes" in the T cell repertoire - genes
encoding MHC and TcR lack of specificity and/or
lack of positive selection -"high" and
"low" responders -F1 (high x low) high
responder........return to the "pan" -low
??(low x high) chimera -generation of the
available peripheral T cell repertoire is
dependent on MHC expressed in the thymus
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Julius Lecture III (continued) (v) The TcR/CD3
Complex -elements of the CD3 complex regulate
TcR expression -elements of the CD3 complex
regulate TcR function -signalling and the
concept of "second messengers" (vi) CD4 and
CD8 -adhesion molecules for MHC class I and
MHC class II -expression correlates with TcR
specificity (NOT FUNCTION!) i.e. CD4-MHC
class II and CD8-MHC class I -multiple receptor
interactions mediate T cell activation- the role
of CD4 and CD8 as "co-receptors" -the
protein tyrosine kinase p56Lck
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• Julius Lecture III (continued)
• RULES WHEN THINKING ABOUT CHIMERAS
• MHC of stem cells used to reconstitute the host
  will be the MHC expressed by daughter T cells, B
  cells, and APCs.
• MHC of intra-thymic stem cells and developing T
  cells will "negatively" select those T cells
  expressing self-reactive (self MHC) TcR (T cell
  receptor for antigen)
• MHC expressed on the thymic epithelium will
  "negatively" select those T cells expressing
  self-reactive TcR which are not deleted by donor
  stem cells compare F1?P1 and P1?F1chimeras
• MHC expressed on the thymic epithelium will
  "positively" select those T cells expressing TcR
  able to recognize antigen in the context of
  self-MHC. Positive selection will thus determine
  the available T cell repertoire in the periphery
  of the animal N.B. remember the low
  responder?high responder (F1)chimera
• MHC expressed by APC in the periphery of the
  animal will determine whether a T cell will be
  activated and expanded see (i)

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Julius Lecture IV (i) Intra-thymic T cell
development -TcR specificity sets the stage
(i.e. MHC class I or MHC class II) -double
positive thymocytes are precursors of single
positive (CD4 or CD8) thymocytes -positive
selection results in down regulated expression of
either CD4 or CD8 -two models of T cell
development (ii) T Cell Dependent Humoral
Responses T-B Collaboration -the players a T
cell clone and splenic B cells with contained
APCs -the "plaque forming cell" (PFC)
assay -separation of T and B cell
specificities hapten-carrier -the requirement
for linked recognition (LR) - notion of the
"antigen bridge" -given that th?TH requires an
MHC restricted interaction with APC, is the
TH?B interaction also MHC restricted? -the
answer is YES......reassessment of the
requirement for LR ? the antigen specific LTP B
cell indirectly acquires antigen for which the
TH is specific, and MUST express the MHC which
restricts TH function
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Julius Lecture IV continued (iii) "Non-Specific"
Ig The Bystander B cell Response -"background"
Ig secreting cells in non-deliberately
immunized animals -T-dependent and
T-independent immune responses -conversion of
a T-dependent to a T-independent response
using a T- independent carrier -demonstration
that induction of "non-specific" Ig production
is T-dependent -demonstration that the
induction of "non-specific" Ig does not require
LR -demonstration that the lack of requirement
for LR correlates with the lack of requirement
for MHC restricted TH?B interaction -B cells
giving rise to "non-specific" Ig are not
contained within the population of LTP DNP
specific B cells???????? -what is happening to
DNP specific B cells in LTP animals?
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Julius Lecture V (i) The State of B cell
Activation susceptibility to lymphokines -B
cell separation into high buoyant density
(resting) and low buoyant density (activated)
subsets on discontinuous density gradients
density? -requirement for an MHC restricted
TH-B interaction depends on the state of B
cell activation (ii) Cytokine function does not
require cell contact -the bystander B cell
response revisited -conversion of a B cell
response from that which requires LR and an
MHC restricted interaction with TH, to one
which requires neither -derivation of antigen
specific B cells from long term primed and
boosted animals (iii) Lymphokines and
Cytokines soluble mediators of cell activation
and differentiation -an "autocrine" loop for T
cell growth and differentiation -th-APC contact
induced expression of high affinity receptors
for IL-2 (IL-2R) on ensuing TH and IL-1
production by APC -if affinity of th-APC
interaction is sufficiently high, ensuing TH
will also express receptors for IL-1
(IL-1R) -TH consumption of APC derived IL-1
potentiates the production of IL-2 by TH -TH
produce and utilize their own growth factor, i.e.
autocrine growth loop -activated T cells
produce IL-4 and IL-5 as well as IL-2 -IL-4
induces de novo transcription and translation of
MHC class II of B cells and thus potentiates
MHC class II restricted TH-B interaction -IL-5
supports differentiation of resting B cells, and
in combination with IL-2 supports the growth
and differentiation of activated B cells
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• Julius Lecture V continued
• (iv) Does TcR-MHC Class II interaction provide
  the B cell with critical activation signals CD40
  and gp39
• The preparation of a monoclonal antibody (mAb)
• RULES WHEN THINKING ABOUT TH-B COLLABORATION
• Can th be activated? This always requires an MHC
  restricted interaction
• with APC
• Are APC expressing the appropriate MHC present,
  and is antigen for th present?
• (ii) Activated TH produce lymphokines, the
  function of which are not MHC restricted.
• (iii) Check the state of activation of the B
  cells present resting high ?B cells are
  refractile to lymphokine mediated growth
  activated low ? B cells are sensitive to
  lymphokine mediated growth and differentiation.
• (iv) High ? B cells require an MHC restricted
  TH-B interaction and thus LR low ??B cells
  require neither.