Helper T Cells and Their Response to Antigen Flashcards
(42 cards)
What are the four major populations of lymphocytes with antigen-binding receptors and their roles?
Helper T cells - regulate immune responses
Effector or cytotoxic T cells - destroy cells expressing endogenous antigens
Regulatory T cells - control everything
B cells - produce antibodies
Exogenous antigen is trapped and processed by _________ and other ______________ and then presented to ____________.
Exogenous antigen is trapped and processed by dendritic and other antigen-presenting cells and then presented to helper T cells.
If a helper T-cell receptor binds an antigen in the correct manner, the helper T cell is activated and initiates an immune response by ___________, _________, and _____________
If a helper T-cell receptor binds an antigen in the correct manner, the helper T cell is activated and initiates an immune response by secreting cytokines, dividing, and differentiating
Other antigen-responsive cell populations, the ________ and the ______________, cannot respond to antigens unless they are stimulated by helper T cells.
Other antigen-responsive cell populations, the B cells and the cytotoxic T cells, cannot respond to antigens unless they are stimulated by helper T cells.
Important proteins with multiple domains include the ____________________, the ____________________, and the _______________________.
Important proteins with multiple domains include the B cell antigen receptors (BCRs), the T cell antigen receptors (TCRs), and the MHC class I and II molecules.
The four key antigen receptors of the immune system are each constructed using ______________ as building blocks. Each binds antigen through the use of ___________. All are members of the __________________.
The four key antigen receptors of the immune system are each constructed using immunoglobulin domains as building blocks. Each binds antigen through the use of variable domains. All are members of the immunoglobulin superfamily.
The N-terminal of the TCR is called the…
variable domain
The C-terminal domain within the cytoplasm of the T cell is called the….
transmembrane domain
The paired chains are joined by a ____________ between their _____________________ to form a stable heterodimer.
The paired chains are joined by a disulfide bond between their constant domains to form a stable heterodimer.
What is the hypervariable or the complementary determining region (CDR)?
region with highly variable amino acid sequence
comes into contact with the antigen
The two antigen-binding chains of each TCR are associated with a cluster of signal transducing proteins called the
CD3 complex
The TCR β chain is linked to the _______ dimer, and the TCR α chain is linked to the ________ dimer
β chain - γ-ε (gamma, epsilon)
α chain - δ-ε (delta, epsilon)
About 80% of α/β TCRs use ____ dimers. The remaining 20% use _____ heterodimers.
About 80% of α/β TCRs use ζζ (zeta, zeta) dimers. The remaining 20% use ηζ (eta, zeta) heterodimers.
CD4, found only on ____________, binds ____________ molecules on _______________ cells.
CD4, found only on helper T cells, binds MHC class II molecules on antigen presenting cells.
CD8 is found only on ___________ and binds ___________ molecules on ______________ or ______________.
CD8 is found only on cytotoxic T cells and binds MHC class I molecules on virus-infected or abnormal cells.
______ and ______ enhance TCR signal transduction 100-fold when they cross-link to an MHC molecule on an antigen-presenting cell
CD4 and CD8 enhance TCR signal transduction 100-fold when they cross-link to an MHC molecule on an antigen-presenting cell
What is a ligand
a signal-triggering molecule binding to a site on a target protein
Induction of Th17 cells occurs by exposure to a cytokine mixture containing ________ and _________. Differentiation is promoted by _________ and maintained by _______. Th17 cells promote ___________.
Induction of Th17 cells occurs by exposure to a cytokine mixture containing TGF-β and IL-6. Differentiation is promoted by IL-21 and maintained by IL-23. Th17 cells promote inflammation.
Unlike conventional antigens that must bind within the grooves of both an MHC molecule and a TCR, ____________ directly link a TCR Vβdomain to an MHC class II molecule on the antigen-presenting cell.
superantigens
Superantigens (SAgs) are a class of antigens that cause ___________ activation of T-cells resulting in polyclonal T cell activation and massive ____________. SAgs are produced by some ____________ and _____________.
Superantigens (SAgs) are a class of antigens that cause non-specific activation of T-cells resulting in polyclonal T cell activation and massive cytokine release. SAgs are produced by some viruses and bacteria.
The differentiation of ______ cells is driven by IL-12 produced by antigen-presenting _____________ cells (DC1), macrophages (M1), and B cells plus co-stimulation by CD80.
The differentiation of Th1 cells is driven by IL-12 produced by antigen-presenting myeloid dendritic cells (DC1), macrophages (M1), and B cells plus co-stimulation by CD80.
Th1 cells promote _____________ immune responses such as the delayed hypersensitivity reaction and macrophage activation. They thus generate immunity to ___________ organisms such as mycobacteria and to viruses
Th1 cells promote cell-mediated immune responses such as the delayed hypersensitivity reaction and macrophage activation. They thus generate immunity to intracellular organisms such as mycobacteria and to viruses
Dendritic cells that do not secrete IL-12 promote __________ cell differentiation
Th2
Th2 cells respond optimally to antigen presented by_____________________ (______ cells) and macrophages, and less well to antigen presented by B cells
Th2 cells respond optimally to antigen presented by plasmacytoid dendritic cells (DC2 cells) and macrophages, and less well to antigen presented by B cells
