Lecture 2 Flashcards
(35 cards)
What is a leukocyte?
Nucleated cells of the blood; white blood cells. When you centrifuge anticoagulated blood, they sediment on top of the packed red cells, forming the “buffy coat.”
Mononuclear cells
Leukocytes whose nucleus has a smooth outline; monocytes (immature, becoming mature macrophages in the tissues/phagocytes/can present to t-cells), and lymphocytes (large nucleus inside/T-Cell/B-cell). In tissues it’s sometimes hard to tell the difference between macrophages and lymphocytes, hence the blanket term “mononuclear.”
Polymorphonuclear cells
Cells whose nucleus is lobulated, also called granulocytes because they have (usually) rather prominent cytoplasmic granules. They are:
Eosinophils; Basophils (closely related to tissue mast cells); and Neutrophils.
Plasma cell
a B-cell that is activated and spits out an antibody
Granuloctyes
Also called polymorphonuclear cells; have cytoplasmic granules
Monocyte
mononuclear;
phagocytic cell
can also present to T-cells (so that would be part of specific)
-can become macrophages
Lymphocyte
Mononuclear; large nucleus; -T-cell and -B-cell
neutrophil
polymorphonuclear; first responders/puss
Eesonophils
polymorphonuclear; look like “sunglasses”; parasites, allergy, asthma
Basophils
polymorphonuclear; two nuclei and granules (that are full of histamine)
Mast cells
Like a basophil (granules with histamine); however basophils are in blood and mast cells are in tissue
serum
plasma without fibrinogens
main central lymph organs
Central organs are ones in which lymphocytes develop: the bone marrow and the thymus. (In mammalian embryos, bone marrow function is first found in the yolk sac and then in the liver.)
Peripheral lymph organs
In the peripheral organs, mature cells are organized to trap and respond to foreign invaders:
these organs include lymph nodes, spleen, Peyer’s patches and mesenteric lymph nodes of the gut, tonsils and adenoids. MALT/GALT
At any moment many lymphocytes are found in the blood and lymph, too, but most are in the peripheral lymphoid organs.
Antigen
a substance which can be recognized by the immune system.
An antigen frequently is also an immunogen, which is an antigen in a form which can give rise to an immune response, that is, which can immunize.
An antigen can also be a toleragen (no immune response)
epitope
The part of the antigen that we see and can ID as foreign (a good antigen an antigen repeated over and over). Can also be called an antigenic determinant
How to antigens activate lymphocytes?
immediate: neutrophils, monocytes–> macrophages and phagocotize; maybe we stop here or keep going…
if we keep going, dendritic cells (the bridge between);
the DC presents antigen: DC excretes cytokines (activate other parts of the immune system)
then goes to lymph node and present antigen to B and T cells
Define toleragen
tolerogen is antigen delivered in a form, or by a route, which does not give rise to an immune response, and which furthermore prevents an immune response to subsequently administered immunogen which has the same antigenic determinants—to be discussed later.
Describe the pattern of lymphocyte recirculation
a lymphocyte in the blood encounters the cells lining certain postcapillary venules in the peripheral lymphoid tissues, especially lymph nodes.
These endothelial cells are unusual⎯not flat as is the usual case, but high and cuboidal.
Recirculating lymphocytes may bind to and pass between the endothelial cells into the lymph node, where they may stay, or move eventually into the lymph which drains from that lymph node to the next in the chain. Lymph works its way into the largest lymph channels such as the thoracic duct near the heart; from there it is emptied into the venous blood and the circulatory loop can start over again.
Thus there are two lymphocyte circulations, blood and lymphatic, in which lymphocytes cross from blood to lymph at the nodes, and from lymph back to blood at the heart.
What are the specialized features of lymph node blood vessel endothelium that permit recirculation.
Unusual endothelial cells in post-capillary venules in the peripheral lymphoid tissues (e.g. lymph nodes); they are not flat—the lymphocytes can bind to them and pass in between them into the lymph node—eventually if it goes into the lymph it will be dumped into the venous blood.
Discuss lymphocyte activation by antigen with respect to: receptor binding, proliferation, differentiation.
(RECEPTOR BINDING)
Each lymphocyte has receptors for antigen; (thousands on each cell); all are identical so that each cell has just a single specificity, different from nearly all the others.
T cell receptors are composed of alpha and beta chains;
B cell receptors are samples of the antibodies that the cell will eventually secrete.
The part of an antigen that fits into the receptor is the antigenic determinant or epitope. To activate the T or B cell several conditions must be met: the fit between receptor and the antigen it sees must be good (specific) enough, several nearby receptors must be simultaneously bound by antigen, and other cell surface molecules must be involved too (accessory interactions or costimulation).
Discuss lymphocyte activation by antigen with respect to: receptor binding, proliferation, differentiation.
(PROLIFERATION)
Once the cell is correctly activated it begins to proliferate. Lymphocytes can divide as fast as every 6 hours, so in just a few days you have thousands of cells specific for the antigen that got the process started.
Discuss lymphocyte activation by antigen with respect to: receptor binding, proliferation, differentiation.
(DIFFERENTIATION)
These cells also differentiate: into effectors that do the job (B cell blasts and plasma cells that release antibodies into the blood; helper T cells that pour out cytokines; killer T cells that induce their targets to die) and into memory cells that recirculate efficiently and are very easily triggered by another exposure to antigen.
Humoral (antibody) vs. cell mediated immunity
Lymphocytes involved:
nature of the molecules they release:
types of inflammatory cells they preferentially involve:
Lymphocytes involved:
cell-mediated involves T-cells; can’t transfer person to person (they see antigen on antigen presenting cell) and can kill
humoral involves B-cells; plasma cells, secrete antibodies
nature of the molecules they release:
types of inflammatory cells they preferentially involve:
