T cells

Question 1

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

Answer 1

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

Question 2

Lymphoid system includes?

Answer 2

– Lymphatic vessels
– Secondary lymphoid organs
– Primary lymphoid organs

Question 3

Lymphatic vessels do what?

Answer 3

– 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

Question 4

Primary lymphoid organs are?

Answer 4

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

Question 5

Secondary lymphoid organs are?

Answer 5

– 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

Question 6

During lymphocyte development, B and T cells

acquire ability to?

Answer 6

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

Question 7

Antigen (Antibody generator): compound that elicits an

adaptive immune response. Can be bound by?

Answer 7

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

Question 8

Cellular immunity is Mediated by T cells

Answer 8

– 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

Question 9

T lymphocytes derive from the?

Answer 9

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

Question 10

T lymphocyte development

Answer 10

– 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)

Question 11

T lymphocyte clonal expansion

Answer 11

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

Question 12

T Lymphocyte characteristics include

Answer 12

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

Question 13

Strategy of Adaptive Immune Response

Answer 13

3 types of APCs:

1. DC
2. Macrophage
3. B cell