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Flashcards in T cells Deck (13):

The Lymphoid System is a Collection of tissues and organs designed to?

bring B and T cells in contact with antigens
– To mount appropriate response, immune cells must
encounter antigen


Lymphoid system includes?

– Lymphatic vessels
– Secondary lymphoid organs
– Primary lymphoid organs


Lymphatic vessels do what?

– Carry lymph to body tissues
* Lymph formed through actions of the circulatory system
– Lymph travels through vessels to LNs
* Material is removed (cells, proteins)
– Fluid portion empties back into blood stream


Primary lymphoid organs are?

– Bone marrow and thymus are primary lymphoid
* Location where stem cells mature into naïve T or B
– B cells mature in bone marrow
– T cells mature in thymus
* Once mature, lymphocytes leave primary lymphoid organs and migrate to secondary lymphoid organs


Secondary lymphoid organs are?

– Sites where lymphocytes gather to encounter antigen
* Lymph nodes
* Spleen
* Tonsils
* Adenoids
* Appendix
* MALT; Peyer’s patches
– Organs situate strategically
* Allows for initiation of immune response from nearly any
place in body


During lymphocyte development, B and T cells
acquire ability to?

recognize distinct epitopes
– T cells go through this process in the thymus
– T cells must recognize a peptide in the context of th MHC molecule


Antigen (Antibody generator): compound that elicits an
adaptive immune response. Can be bound by?

specific BCR (antibody) or TCR
* TCR antigens are peptides held by MHC
* The epitope is the part of antigen that the TCR (or BCR/antibody) binds to


Cellular immunity is Mediated by T cells

– T cell receptors allow antigen recognition
– Divided into 2 subsets
1) Cytotoxic T cells = CD8+ = TC cells
-Kill target host cells
2) Helper T cells = CD4+ = TH cells
-Th1, Th2, Th17 are specialized subsets
-Support and direct B cells, T cells and macrophages


T lymphocytes derive from the?

bone marrow hematopoietic stem cells, but mature in the thymus.


T lymphocyte development

– 98-99% of T cells in the thymus die
– 2 keys to survival:
1. TCR must not be self-reactive (negative selection)
2. TCR must recognize host MHC (positive selection)


T lymphocyte clonal expansion

Clonal Expansion = proliferation of cell
– 2 signals required, both delivered by activated DC:
1. MHC:peptide recognition by TCR
2. Co-stimulation from DCs
– Cell surface proteins get expressed only once DC has TLR stimulation


T Lymphocyte characteristics include

1) Naïve
* Have antigen receptor but have not encountered antigen
2) Activated
* Able to proliferate
* Have bound antigen
3) Effectors
* Descendants of activated lymphocytes
* Able to produce specific cytokines
* Now can act as TC or TH cells
4) Memory lymphocytes
* Long-lived descendants of activated lymphocytes
*Memory cells responsible for speed and effectiveness of secondary response
– Remembers antigen upon subsequent exposure


Strategy of Adaptive Immune Response

3 types of APCs:
1. DC
2. Macrophage
3. B cell