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Micro lecture 11
| Question | Answer |
|---|---|
| The antigen-antibody interaction is specified by what region of the antibody? | The variable region. |
| The effector function of the antibody is specified by what region? | The constant region. |
| What's the DNA rearrangement for the light chain? | V-J joining. |
| What's the DNA rearrangement for the heavy chain? | V-D-J joining. |
| Further DNA rearrangement in the heavy chain results in what? | Class switching. This leads to a new constant region, which leads to a new effector function of the antibody. |
| Each B cell has it's own _________ light and heavy chains. This leads to particular antigen recognition specificity. | Unique (or particular) |
| When is a naive B cell activated? | When it encounters an antigen that is recognized by BCR. |
| What does activation of a B cell lead to? | Proliferation (clonal expansion) of the B cell. |
| What happens during clonal expansion? | 1. Antibody class switching 2. Affinity maturation 3. B cell turns into antibody-secreting plasma cells 4. Development of memory B cells |
| What can antibodies recognize? | soluble and membrane bound antigens; proteins/peptides, small molecules, nucleic acids, etc. |
| Different classes of antibody have different _________ _________. | Effector functions. |
| T-cells have 2 chains, a and B, each with a single ________ ________ and a single ________ ________. | variable region; constant region |
| A naive T-cell is activated when it comes in contact with an antigen that is recognized by ___. | TCR |
| What does TCR recognize? | only peptide antigens; only antigens that are presented by MHC I or II molecules. |
| Single chain plus a B2-microglobulin chain; expressed on virtually all nucleated cells; presents peptide antigen from the endogenous pathway; presents peptide antigen to CD8+ T-cells | MHC Class I |
| 2 chains; expressed on APCs (dendritic cells, macrophages, B cells); presents peptide antigen from the exogenous pathway; presents peptide antigen to CD4+ T-cells | MHC Class II |
| CD | Cluster of Differentiation; Cell surface molecules that can be used to identify leukocytes of different lineages or different stages of differentiation. |
| What are the steps of T-cell maturation? | Pro T-cell; Double negative (CD4- CD8-); TCR rearrangement (B); Double positive (CD4+ CD8+); TCR rearrangement (a); Split to single positives CD4+ and CD8+; leave the Thymus as naive T-cells |
| T-cells are "trained" as they travel to the thymus in 3 ways. How? | Positive selection; Lack of positive selection; Negative selection. |
| Positive selection (T-cells) | Recognition of peptide-MHC complex on thymic epithelial cell leads to rescue from apoptosis and conversion to a single positive. |
| Lack of positive selection (T-cells) | Failure to recognize peptide-MHC complex on thymic epithelial cell leads to apoptosis. |
| Negative selection (T-cells) | Recognition of peptide-MHC complex on thymic antigen-presenting cell leads to apoptosis. |
| What are the 2 signals to activate T-cells? | 1. TCR engages in antigen + self MHC 2. Co-stimulation by CD28 (on T cell) and B7 (on APC) |
| What does T-cell activation induce? | IL-2 and IL-2 receptor production. |
| What does IL-2 do? | Leads to cell proliferation. |
| What is the result of IL-2 induced cell proliferation? | Production of effector and memory cells. |
| Effector and Memory T-cells require only ______ ___ to activate, unlike regular T-cells. | Signal 1. |
| What do Dendritic Cells (DCs) do in nonlymphoid organs? | Immature DCs serve as sentinels that capture antigens by phagocytosis, endocytosis, and pinocytosis. |
| The DCs mature into ______ and migrate to the secondary lymphoid system where they present antigen to T-cells on MHC class II and I. | APCs |
| What do DCs do in lymphoid organs? | Receive antigens from lymph, blood, or immigrant DCs, relaying antigen from the periphery to T cells. |
| Naive cells recirculate through the ____ _____ _____ to up their chances of meeting an antigen. | secondary lymphoid tissues. |
| Memory/mature cells can go _______. | anywhere |
| When a DC meets a naive T-cell, what happens? | Activates T-cell, causes clonal expansion and differentiation of T-cells into effector T-cells. |
| When a macrophage meets an effector T-cell, what happens? | The effector T-cell is activated, the macrophage is activated. |
| When a B-cell meets an effector T-cell, what happens? | Activates effector T-cell, activates B-cell, produces antibodies. |
| What's the effector function of CD8+ T cells? | Kill the target cell. Targets: virus infected cells, altered self cells, other intracellular pathogens. |
| What's the effector function of CD4+ T cells? | Get help, promote an adaptive response or increase response potency. Targets: extracellular pathogens, foreign particles, toxins, etc. |
| CD8+ (a CTL) uses _________ and _________ to kill cells. | perforin; granzymes |
| What is a CTL? | Cytotoxic T Lymphocyte; they kill target cells. Targets: Virus-infected cells, organ transplants, cancer cells, normal cells in some autoimmune diseases |
| What is Fas/FasL killing? | Activation of Fas activates the apoptotic pathway. |
| CD4+ T cells produce cytokines that... | 1. Stimulate CTL differentiation 2. Activate macrophages 3. Stimulate B-cell proliferation, affinity maturation, and differentiation into memory B-cells. |
| CD4+ T cell subclasses are distinguished by the ___________ they produce. | cytokines |
| TH1 | Developed in response to IL-2 and IFNγ; Secretes IFNγ and other cytokines to stimulate macrophages; activate CD8+ T cells and NK cells. |
| TH2 | Develop in response to IL-4; Help B cells respond to T-dependent antigens by secretion of antibodies; Secrete IL-4, IL-5, directing B-cell class-switching to IgG or IgE. |
| TH17 | used against fungi and extracellular bacilli |
| Treg | inhibits T-cells to prevent autoimmunity |
| Bring antigens and APCs from peripheral tissue to the lymph node | afferent lymph nodes |
| cortex (lymph node structure) | mostly B cells, macrophages, follicular dendritic cells |
| paracortex | T cells and DCs for antigen presentation |
| Medulla | antigen-secreting plasma cells |
| T-cells ______ B-cells | help |
| Cytokines provided by T-cell help guide what? | isotope switching in B cells |
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