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What cells have CD4?
- CD4 - Helper T Cells
- CD8 - Cytotoxic Cells
What cells are effected by Natural Killer Cells and gd T lymphocytes?
By what mechanism?
- Tumor cells or virally-transformed cells
- Release perforins and fragmentins or cytokines
What defines an Antigen Presenting Cell?
- Must express MHC Class II
- Langerhans' cells in epidermis
- Reticular dendritic cells of spleen/lymph nodes
Define Antigen processing
Intracellular conversion of native proteins into peptides and loading onto MHC molecules
What presents endogenous antigens?
Where does antigen processing take place?
- MHC Class I
- Virally infected cells, tumor antigens
- Occurs in cytoplasm of infected/tumor cells
What presents exogenous antigens?
- MHC Class II
- Bacterial infection
What are the two types of cytokines and their associated responses?
- Pro-inflammatory - cellular immune response
- Anti-inflammatory - humoral immune response
Describe the mechanism of interferons
- Produced by virally infected cells
- Activate natural killer cells
What are lymph nodules?
- Unencapsulated lymphoid tissue
- MALT, GALT, BALT
What are the structural and functional differences between primary and secondary nodules (follicles)?
- Secondary nodules have pale Germinal Center, contains B-lymphoblasts (active proliferation)
- Primary nodules - densely packed small lymphocytes
What are Peyer's pathes and their associated structures?
- Unencapsulated lymph nodules in ileum
- Contain high endothelial venules (blood vessels)
- M (microfold) cells - endocytose antigens
1. Are tonsils encapsulated?
2. Describe the crypt structure of different tonsils
1. Yes - dense connective tissue capsule
- 2. Palatine tonsil - 10 to 20 deep crypts
- Pharyngeal tonsil (adenoid) - no crypts
- Lingual tonsil - single crypt
What are the function of lymph nodes?
Reaction to antigens presented to B lymphocytes by macrophages and follicular dentritic cells
Extensions of the capsule into the lymph tissue
What are the structural framework cells/fibers of lymph nodes?
Describe the path of lymph in a lymph node
- Afferent lymphatic capillaries -->
- Subcapsular sinuses -->
- Trabecular sinuses -->
- Medullary sinuses -->
- Efferent lymphatic vessel
Where do B cells differentiate?
Interfollicular spaces in the cortex of lymph nodes
Where are T Cells located in lymph nodes?
Deep dense paracortical area
Describe the splenic features:
1. White pulp
2. Periperal white pulp
3. Red pulp
4. Marginal zone
- 1. T-lymph in Periarteriolar lymphatic sheaths (PALS), B-lymph in nodules
- 2. B-cell area in white pulp
- 3. Splenic cords and sinusoids
- 4. Area between white and red pulp containing APCs
Does the thymus have germinal centers or nodules?
What tissue forms the thymus?
Endoderm - epithelial reticular tissue
What is thymic education and where does it take place?
- Maturation of lymphatic stem cells
What prevents foreign antigens from reaching the thymic cortex?
Blood-thymic barrier (type I cells)
What are the types of epithelioreticular cells?
- Type I - blood thymic barrier
- Type II - express MHC I/II
- Type III - express MHC I/II, cortex/medulla barrier
- Type IV - cortex/medulla barrier
- Type V - ?
- Type VI - for Hassel's corpuscles (produce thymic hormones)