January 24 Notes

Immunology, January 24, 2008

I. Lymphoid tissues
a. Primary- tissues where lymphocytes are initially made and where they differentiate
Ex. bone marrow (b-cells) and Thymus (t-cells)
b. Secondary- where antigens are specifically introduced to B- and T- cells
Ex. lymph nodes, spleen, mucosal-associated lymphoid tissues (MALT)
i. chemokines- signalling molecules that help/lead to differentiation of "normal" tissue to secondary lymphoid
* secreted by immune cells
c. Tertiary- ectopic secondary lymphoid tissue created due to chemokines secreted by active immune cells
* found in tissues with chronic inflammation
d. Lymphatic vessels-
*afferent- flows from the tissues towards the lymph nodes
* efferent- flows from lymph nodes (and other secondary tissues) to the bloodstream.
II. Secondary lymphoid tissues
a. Lymph nodes
*Immature dendritic cells
-not exposed to antigens
*Mature dendritic cells
-presenting antigens on surface
-came into contact w/ antigen in blood stream
-Migrated to lymph nodes through lymph vessels
(See Fig 1-19 pg 15 for lymph node diagram)
i. Dendritic cells- myeloid lineage
-antigen-presenting for T-cells
ii. Follicular dendritic cells
-antigen-presenting cells for B-cells
-Not of same lineage of any other immune cell (not from hemapoetic stem cell)
b. Spleen
-filters ALL blood
-Recycles damaged or old RBCs
-Introduction of B-cells and T-cells to antigens
i. Red pulp
*marginal zone macrophages
*metallophilic macrophages
-process iron and heme from recycled RBCs
*marginal zone B-cells
-rapid antibody response against bloode-borne bacteria
ii. White pulp
*lymphoid tissue part of the spleen
*germinal centers
-rapid proliferation of B-cells
c. Mucosa-associated lymphoid tissues (MALT)
i. Peyer’s patches
*secondary lymphoid tissue in small intestine
*gut is exposed to LOTS of antigens
1. M-cells: specialized gut epithelial cells that sort of behave like macrophages
*ingest antigens, pass across cytoplasm without digesting, "hand off" to dendritic cells on other side
III. Course of an immune response to: Guinea Worm
a. Exposure- ingestion
i. Barriers to infection: mucus, acid, enzymes, and epithelial
b. Innate immune responses
i. macrophages- engulf
ii. eosinophils- uses antimicrobial chemicals
iii. cytokines- inflammation
iv. dendritic cells- engulf and present antigens of the guinea worm
c. Activation and differentiation of T-cells: only recognize proteins presented on MHC II receptors on dendritic cells
**T cells differentiate into mature T-cells and undergoes clonal expansion
d. Activation and differentiation of B-cells: interact with T-helper cells presenting antigens of guinea worm
** B cells undergo clonal expansion and differentiation
e. Death of lymphocytes- over 99% of those that participate in response die!
* couple of days after pathogen clearance
* Immune response amplify themselves- secrete molecules to attract more
* Death is important so immune response doesn't lead to death of the host/infected person
f. Resting memory cells-small minority of lymphocytes enter quiescent stage (not dividing)
* can live in this state for at least 60 years
* plasma cells- secreting low levels of those specific antibodies
-level decreases over time/years
Medical application: Antibody Titer testing-1. take blood sample.
2. run ELISA to determine concentration of antibody against particular antigen
* too low= booster vaccines
TB Test-Looks for cell mediated immunity (T-cell recognition of intracellular pathogen components presented on MHC-I)…inject TB antigen which recruits the CD8+ T cells which have been in the quiescent stage.

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