Download 7th Lecture

Survey
yes no Was this document useful for you?
   Thank you for your participation!

* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project

Document related concepts

Phagocyte wikipedia , lookup

Lymphopoiesis wikipedia , lookup

Hygiene hypothesis wikipedia , lookup

T cell wikipedia , lookup

DNA vaccination wikipedia , lookup

Immune system wikipedia , lookup

Molecular mimicry wikipedia , lookup

Adaptive immune system wikipedia , lookup

Cancer immunotherapy wikipedia , lookup

Immunosuppressive drug wikipedia , lookup

Innate immune system wikipedia , lookup

Adoptive cell transfer wikipedia , lookup

Polyclonal B cell response wikipedia , lookup

Psychoneuroimmunology wikipedia , lookup

Immunomics wikipedia , lookup

Transcript
PHL 633 Immunotoxicology
Seventh Lecture
By
Abdelkader Ashour, Ph.D.
Phone: 4677212
Email: [email protected]
Acquired Immune Responses, Cell mediated
 Macrophages and dendritic cells (including Langerhans cells in the skin) and
Kupffer cells in the liver, have an important role in the development of specific
immune responses to pathogens in that they process and present antigens to
T lymphocytes
 The T- cell antigen receptor (TCR) recognizes and binds proteolytically
processed short peptide fragments (antigens) bound to self major
histocompatibility complex (MHC) molecules on the surface of an APC
 There are two major classes of MHC molecules that present different types of
antigens to different types of T cells:
I. Class I MHC generally presents peptides derived from proteins produced
within the cell (e.g., viral or tumor antigens) and is recognized by CD8 T cells
II. Class II MHC generally present peptides derived from proteins taken up by the
cell and is recognized by CD4 T cells
 In addition to the TCR, other molecules contribute to activation of T cells either
by functioning as co-receptors that initiate nonspecific, co- stimulatory signal
transduction events or by increasing the avidity of the interaction with the
antigen-presenting cell
Acquired Immune Responses, Cell mediated
Acquired Immune Responses, Cell mediated
Acquired Immune Responses, Cell mediated
Acquired Immune Responses, Cell mediated
 Binding of antigen presented on MHC to a TCR is the major interaction that
must occur between APCs and T cells to initiate an acquired immune response
 Subsequent to this initial interaction, costimulatory molecules must be
engaged on both the T cells and APCs to sustain and direct the immune
response
 One of the best characterized interactions occur between CD28 on the T cells
and B7.1 (or CD80) on the APCs, which provide a more robust immune
response as measured by clonal expansion and cytokine production, such as
IL-2
 Other important interactions between cells include CD40–CD40 ligand (on
APC–T cell, respectively), which sustains clonal expansion and differentiation
of the T cells, and provides activation signals to the APC
 Other important interactions between cells include CD40–CD40 ligand (on
APC–T cell, respectively), which sustains clonal expansion and differentiation
of the T cells, and provides activation signals to the APC
Acquired Immune Responses, Cell mediated
Acquired Immune Responses, Cell mediated
Acquired Immune Responses, Cell mediated
Acquired Immune Responses, Cell mediated
 T cells that express CD8 mediate cell killing (CTL); whereas T cells that
express CD4 mediate helper functions through coordinated interactions with
other cells
 A recently described population of T cells, the T-regulatory cells, are a subset of
CD4+ T cells that express CD25 and the transcription factor Foxp3
 These cells act to suppress T-cell function and prevent uncontrolled immune
responses
 Mature T cells are found in the lymph nodes, spleen and peripheral blood
 Upon MHC plus antigen binding to the TCR, the mature T cell becomes
activated and, after proliferation, undergoes differentiation into either an
effector cell or a memory T cell
 Effector T-helper cells can subsequently differentiate into either a Th1 or a Th2
phenotype
 Th1 cells predominantly express IL-2 and IFN-γ and promote CMI and
delayed-type hypersensitivity (DTH)
 Th2 cells predominantly express IL-4, IL-5, IL-6, IL-10, and IL-13 and promote
humoral immune responses. Although the two populations are not mutually
exclusive, they do negatively regulate each other, such that a strong Th1
response suppresses a Th2 response and vice versa
Acquired Immune Responses, Cell mediated
Acquired Immune Responses, Cell mediated
Acquired Immune Responses, Cell mediated
Acquired Immune Responses, Cell mediated
Acquired Immune Responses, Cell mediated
Acquired Immune Responses, Cell mediated