Lymphocyte Traffic and Mucosal Immunity Flashcards
Lymphocyte movement in absence of inflammation or specific antigen responses
Naive lymphocytes circulate from generative lymphoid tissues through secondary lymphoid tissues via blood and lymph
How antigen migrates from site of infection to lymph node
Dendritic cells pick up antigen, then migrate from site of infection to lymph node
Where do naive B and T cells circulate?
Secondary lymphoid organs, such as lymph nodes
High endothelial venules (HEVs)
Specialized capillaries of lymphoid tissues where lymphocytes exchange from the blood
What do endothelial cells in HEVs lack?
Tight junctions: make it easier for lymphocytes to pass through
Only what type of immune cells exit the blood and enter the secondary lymphoid tissues through HEVs?
Lymphocytes
Migration into and out of lymph nodes: B and T cells
Enter via blood (HEV), leave via lymphatics
Migration into and out of lymph nodes: APCs and antigen
Enter and leave via lymphatics
Thoracic duct
Lymphatic system drains back into blood via thoracic duct and right lymphatic duct
What causes leukocytes to exit the blood?
Binding to vascular endothelial cells causes them to stop and exit blood at sites of inflammation
Leukocytes exiting blood: steps
- Rolling
- Integrin activation by chemokine
- Arrest/adhesion
- Transendothelial migration
Adhesion molecules
Bind to leukocytes to stop them and enable them to exit blood
Families are based on structure
Do immune cells use the same or different adhesion molecules to regulate their tissue migration?
Different, but overlapping
Vasodilation
Increase of net blood flow resulting in heat, redness, and swelling/edema
Transudate vs exudate
Transudate: fluid escaping the blood vessels during vasodilation
Exudate: extravascular fluid with high protein content, indicative of more severe inflammation
Difference between edema and pus
Edema: less localized or contained
Pus: localized accumulation of white blood cells
What happens during inflammation?
Cytokines promote adhesion molecule expression
5 signs of inflammation
Heat Redness Swelling Pain Loss of function
What will effector lymphocytes do that naive lymphocytes don’t?
Enter tissues
Neutrophils have short lifespans unless they do what?
Enter tissues during inflammation or storage in spleen, liver, or lungs
Neutrophil distribution in the absence of inflammation
Few neutrophils in peripheral tissues except for marginated pools in spleen, liver, and lungs
Does leukocyte migration across the vascular endothelial junction disrupt tight junctions?
No- leukocytes express proteins that interact with tight junction proteins
Lymphocyte homing
Effector and memory lymphocytes home to various tissues depending on which adhesion molecules and chemokine receptors they express
Mucins
Most mucosal tissues are covered with them
Highly glycosylated proteins
Block chemical insults
Trap bioactive molecules such as defensins and IgA
Cilia’s role in the lungs
Move mucus and particles up the respiratory tract where they can be swallowed and eliminated
Main mediator of mucosal immune system
IgA
Poly Ig receptor
Mediates transcytosis of IgA across epithelial lining
Reason why lung infections make it hard to breathe
When airways become inflamed, neutrophils and macrophages accumulate and block exchange of gases
Peyer’s patches
Take up antigen from gut and transport it into draining lymph nodes
M cells
Mucosal lining of gut: site of antigen entry
Immune cells in Peyer’s patches take up antigen that entered through M cells
Transportation of antigen through M cells
Transcytosis enables transport of antigen through M cells
Antigen is then delivered directly to APCs and lymphocytes of mucosal immune system
