63611
| Question | Answer |
| key difference between IgM and IgG with regards to antigen affinity | IgM- many units but weaker affinity. IgG 2 antigens but stronger affinity |
| fas-mediated apoptosis by CTLs | after initial encounter with virus infected cells, CTLs then upregulate FasL which gives an additional weapon |
| perforin inducted apoptosis by CTLs | 1. CTL meets virus infected cell. 2. the large cytolytic granules move toward point of membrane contact. 3. On fusion, granules release perforin, creating pores. 4. Proteases cleave cellular proteins and apoptosis begins |
| CTLs are able to induce programmed cell death (apoptosis) of virus infected cells - 2 pathways | 1. perforin induced apoptosis. 2. Fas mediated apoptosis |
| cytotoxic T cells (CTLs) | 1. express CD8 which binds to MHC-1. 2. generated with help of Th1 cells. |
| how do B cells respond to a repeated challenge? | fast production of IgG antibodies |
| affinity maturation | 1. occurs after class switch. 2. somatic mutations in V regions create variations. 3. better matches differentiate into plasma cells |
| what determines which class the B cell will switch to? | cytokines produced by the helper T cells |
| B cells expressing IgM and IgD are then able to be stimulated by helper T cells and undergo | class switching |
| shortly after antigen exposure and production of IgM, B cells then produce | IgM + IgD |
| naive B lymphocytes respond to first antigen challenge by | synthesis of low affinity IgM antibodies |
| where does antigen dependent clonal selection occur? | in the peripheral lymphoid tissue |
| where does antigen independent clonal selection occur? | bone marrow by gene rearrangement |
| define secondary response | any subsequent encounter with antigen |
| define primary response | first encounter with antigen |
| what is the role of dendritic cells in adaptive immunity? | link innate to adaptive by presenting to T cells |
| primary antibody responses | Naïve B cells, Lag phase, IgM->IgG , Low levels of IgG, Low affinity Ab |
| secondary antibody responses | Memory B cells, No lag phase, IggG, High levels of IgG, High affinity Ab |
| Secreted specific antibodies can: | a) neutralise the antigen by preventing adherance b) opsonise the bacteria -promoting phagocytosis C) activate complement |
| Secretory IgA | Two IgA molecules: are linked by a J (joining) chain; have a SC (secretory component) attached |
| Naïve B lymphocytes respond to the first challenge with the antigen by: | by a synthesis of low affinity IgM antibodies after a log phase. This is followed by affinity maturation and class switch to IgG antibodies |
| Affinity maturation is provided by: | somatic hypermutation in immunoglobulin genes |
| B lymphocytes respond to the repeated challenge with the same antigen by: | a fast production of high affinity IgG antibodies |
| T cell cytotoxicity is mediated by: | Fas/FasL pathway and perforin/granzyme release |
| APC and CD4+ T helper cells provide assistance for: | both effector adaptive responses: antibody production and target cell killing. |
| T cell maturation is regulated by | B cells |
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