VETS2006 Lecture Notes - Lecture 10: Cytotoxic T Cell, Lymph Node, Immunoglobulin Class Switching
Dealing with an invader
Dealing with an invasion
- If a iader gets past the iate iue sste, the it eouters the adaptie
immune system.
- The invading antigens are transported from the site of infection to regional lymphoid tissues
- This transport is commonly conducted by dendritic cells, but may also occur in tissue
macrophages, or as naked antigen.
- B cells and T cells in the lymphoid tissue scan the arriving antigens for their cognate antigen.
- Antigen-specific T cells are activated by antigen-presenting cells, and then activate antigen-
specific B cells
- The activated B and T cells undergo clonal proliferation, producing huge numbers of cells
with the same antigen binding specificity and causing the lymphoid follicles to enlarge and
the lymph node to swell.
- Antigen-specific B cells and T cells continue to interact, migrating back and forward in the
periphery of T-cell and B-cell rich areas of the lymphoid tissue.
- During this period, helper T cells stimulate B cells to undergo affinity maturation, isotype
switching and career choice (to become plasma cells)
- Proliferating B cells are fragile and require on-going activation from helper T cells to survive.
The B cells with the highest affinity for antigen receive most stimulation, the rest undergo
apoptosis.
- The activated antigen-specific B and T cells must now be sent to the site of infection or to
central lymphoid tissues to mount a full-scale response.
- The B cells that become plasma cells move to the medulla of the lymph node, the spleen or
the bone marrow to commence antibody production.
- The T cells move to regions of infection/inflammation or to other lymphoid tissues (i.e.
Places where they are most needed to help B cells and cytotoxic T cells)
- How did the lymphocytes find their cognate antigen, and how do the activated cells now
know where to go?
Lymphocyte Circulation
- Lymphocytes (esp. T cells) are continually travelling through blood and lymph to various
lymphoid organs
- Individual lymphocytes make a complete circuit ~1-2 times per day.
- This process gives lymphocytes the maximum chance that they will meet their cognate
antigen.
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- Naive lymphocytes have a different circulation pattern to activated cells. They patrol widely
throughout the body, entering numerous lymphoid organs and other tissues.
- In contrast, activated lymphocytes have a more restricted route, homing into particular sites
in the body.
- These different trafficking patterns result from the expression of different adhesion
oleules o the T ells’ surfae.
- These adhesion molecules bind to receptors on edothelial cels in particular lymphoid organs
or in inflamed tissues.
- Activated T cells therefore move to regions of infection/inflammation or to particular
lymphoid organs (i.e. Places where they are most needed)
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
If a(cid:374) i(cid:374)(cid:448)ader (cid:862)gets past(cid:863) the i(cid:374)(cid:374)ate i(cid:373)(cid:373)u(cid:374)e s(cid:455)ste(cid:373), the(cid:374) it e(cid:374)(cid:272)ou(cid:374)ters the adapti(cid:448)e immune system. The invading antigens are transported from the site of infection to regional lymphoid tissues. This transport is commonly conducted by dendritic cells, but may also occur in tissue macrophages, or as naked antigen. B cells and t cells in the lymphoid tissue scan the arriving antigens for their cognate antigen. Antigen-specific t cells are activated by antigen-presenting cells, and then activate antigen- specific b cells. The activated b and t cells undergo clonal proliferation, producing huge numbers of cells with the same antigen binding specificity and causing the lymphoid follicles to enlarge and the lymph node to swell. Antigen-specific b cells and t cells continue to interact, migrating back and forward in the periphery of t-cell and b-cell rich areas of the lymphoid tissue.
