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USMLE
Real Immuno 3
Question | Answer |
---|---|
B cells and T cells: Effect on Ig | B cells: Make it T cells: CD4+ cells Help B cells make it and release IFN-gamma to activate macrophages |
B cells and T cells: Method of killing | B cells: IgG opsonizes bacteria and viruses T cells: CD8+ T cells Directly kills virus-infected cells |
B cells and T cells: Allergy mechanism | B: Type I hypersensitivity, through IgE T: Type IV hypersensitivity |
B cells and T cells: Organ rejection speed | B: Fast, through antibodies T: Slow |
CD/MHC: What binds MHC II? | CD4 T-cell receptors |
What does MHC I pair with (allosteric interaction) | beta2-microglobulin |
CD/MHC: What binds MHC I? | CD8 T-cell receptors |
CD/MHC: What binds CD4 T-cell receptors? | MHC II on antigen presenting cells |
CD/MHC: What binds CD8 T-cell receptors? | MHC I on virus-infected cells |
Cytokine effects: Interleukin 1 | Big picture: Stimulates T & B cells, neutrophils, fibroblasts, & epithelial cells to grow, differentiate, synth specific products. Endogenous pyrogen. Upregulates adhesion molecules. Induces acute phase reactants. TNF-alpha synergist. |
What releases: Interleukin 1 | 1. Professional antigen-presenting cells (macrophages, monocytes, dendritic cells, and B cells) 2. Some non-professional antigen presenting cells (fibroblasts, endothelial cells, others) |
How does Interleukin 1 cause fever? | 1.Migrates to the circumventricular organs 2. Binds endothelial receptors 3. Receptors activate Phospholipase A2-COX2-PGE2 pathway 4. PGE2's presence in hypothalamus raises thermoregulatory set point and activates neuroendocrine determinants of fever |
What are the professional antigen presenting cells? | 1. Macrophages 2. B cells 3. Dendritic cells |
What is the CD3 complex? | Cluster of polypeptides associated with a T-cell receptor. It is important in signal transduction. |
How are Th cells activated? | 1. APC phagocytoses F.B. then presents antigen on MHC II 2. Signal 1: Th cell's TCR recognizes antigen. 3. Signal 2 (costimulatory): APC's B7 molecule stimulates Th cell's CD28 molecule. 4. Autocrine IL-2 stimulates Th cell to produce cytokines |
How are Tc cells activated? | 1. Virus-infected cell presents endogenously synthesized proteins on MHC I. 2. Signal 1: Tc cell's TCR recognizes antigen. 3. Signal 2: IL-2 released from Th cell activates T c cell to kill virus infected cell. |
Antibody structure/function: What are the components of the heavy chain? | Variable: VH Constant: CH1, CH2, CH3 |
Antibody structure/function: What are the components of the light chain? | Variable: VL Constant: CL |
What part of an antibody recognizes antigen? | Variable portion of Fab fragment |
What part of an antibody fixes complement? | Constant part of H chain of IgM and IgG |
Antibody structure/function, True or False: Light chain contributes to Fab | True |
Antibody structure/function, True or False: Heavy chain contributes to Fab | True |
Antibody structure/function, True or False: Light chain contributes to Fc | False |
Antibody structure/function, True or False: Heavy chain contributes to Fc | True |
What is the middle of the variable component of an antibody component chain called? | Hypervariable region |
Antibody structure/function: Where on an antibody is the hypervariable region? | The majority of the variable segments excluding the edges |
How are the four chains of an antibody connected? | Interchain disulfide bonds found: 1. between the two heavy chains on the Fc side of the hinge region 2. between corresponding light and heavy chains on the Fab side of the hinge region |
What disulfide bonds does an antibody have? | Interchain: Bonds between both heavy chains and between corresponding light and heavy chains Intrachain: On each segment |
Where on an antibody is the Amino terminal? | At the variable edges of the chains |
Where on an antibody is the carboxyl terminal? | At the constant edges of the heavy chains |
Antibody structure/function: What are the five Cs of Fc? | 1. Constant 2. Carboxy terminal 3. Complement binding (IgG and IgM only) 4. Carbohydrate side chains 5. Complement binding fragment |
3 main functions of the antibody | 1. Opsonization 2. Neutralization (prevents bacterial adherence) 3. Complement activation |
How is antibody diversity generated? | 1. Random recomb of VJ (light chain) or VDJ (heavy chain) genes. 2. Random combination of heavy chains with light chains 3. Somatic hypermutation 4. Addition of nucleotides to DNA during genetic recomb by terminal deoxynucleotidyl transferase |