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USMLE
Real Immuno 1
Question | Answer |
---|---|
Lymph drainage: What does the right lymphatic duct drain? | Right arm and right half of head |
Lymph drainage: What does the thoracic duct drain? | Everything except for the right arm and the right half of head |
Splenic sinusoids: What are they? | Long, vascular channels in red pulp with fenestrated "barrel hoop" basement membrane and macrophages nearby. Adjacent to splenic cords and contain blood. |
How can the spleen be distinguished from a lymph node on histologic section? | Spleens have no subscapsular sinus and no cortex or medulla. They have white pulp and red pulp. |
What does the white pulp of the spleen contain? | 1. Lymphoid follicles with germinal centers (mostly B cells). Can see aggregation of dark basophilic lymphocytic nuclei. 2. Characteristic central arterioles. Surrounded by a Periarterial lymphatic sheath (PALS) which is a collection of T-lymphocytes |
Where is the red pulp of the spleen located? | Around and between the lymphatic nodules of the white pulp |
Splenic cords: What are they? | Structures containing macrophages, plasma cells, lymphocytes, and few RBCs. Separated from each other by splenic sinusoids. |
Thymus: Function | Site of T-cell differentiation and maturation (T cells differentiate in the Thymus. B cells differentiate in the Bone marrow) |
Thymus: Embryological origin | Epithelium of 3rd branchial pouches |
Lymphocytes: Embryological origin | Mesenchyme |
Thymus: What does the cortex contain and what does it look like? | The lobules resemble lymphatic nodules except they are angular, not round. Contains: 1. Densely packed (dark) immature T cells. 2. Large epithelial reticular cells which appear as holes within the cortical cells. |
Thymus: What does the medulla contain and what does it look like? | Pale Contains: Thymic (Hassall's) corpuscles which have a lamellated or whorled appearance due to degenerating epithelial reticular cells. |
What percentage of T cells which enter thymus survive? | 2% |
What is positive selection of T cells? | Selects for T cells able to interact w/MCH. Must bind MHC/self antigen complex w/adequate affinity. Binding MHC too weakly triggers apoptosis signal |
Where do positive and negative selection of T-cells occur in the thymus? | At the corticomedullary junction |
What is negative selection of T cells? | MCH/self antigen presented again. Selects against T-cells that react to strongly to the self-antigen. Binding self too tightly triggers apoptosis signal. |
Innate immunity vs adaptive immunity: How are receptors that recognize pathogens encoded? | Innate: Germline encoded Adaptive: Undergo VDJ recombination during development |
Innate immunity vs adaptive immunity: How fast is response to pathogens? | Innate: Always fast, no memory response. Adaptive: Slow on 1st exposure but memory response is faster and more robust. |
Innate immunity or adaptive immunity: Neutrophils | Innate immunity |
Innate immunity or adaptive immunity: Macrophages | Innate immunity |
Innate immunity or adaptive immunity: Dendritic cells | Innate immunity |
Innate immunity or adaptive immunity: Complement | Innate immunity |
Innate immunity or adaptive immunity: T cells | Adaptive immunity |
Innate immunity or adaptive immunity: B cells | Adaptive immunity |
Innate immunity or adaptive immunity: Circulating antibody | Adaptive immunity |