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NHL for Dummies

First of all, lymphoma is not a disease of the lymphatic system. It is a disease of lymphocytes, a form of white blood cells, which circulate throughout the body in the blood and lymphatic systems.

See below for a description of the lymphatic system:

The lymphatic system and the blood system together form the circulatory system and connect to every part of the body.

Blood cells originate in the bone marrow.

Lymphocytes are the "brain cells" of the immune system. They direct the actions of the other cells involved in fighting off diseases, cancers, etc. When faced with an invader, or simply a damaged cell, lymphocytes reproduce, quite rapidly, in fact, and activate the other parts of the immune system. When this occurs, these lymphocytes are called "reactive." When they've done their job, most of the newly born lymphocytes die an honorable death and things return to normal.

Sometimes, however, a good lymphocyte goes bad. It reproduces and keeps reproducing for no good reason. The newly born lymphocytes don't die an honorable death, but hang on and produce more bad lymphocytes. When this gets out of control, it is called "lymphoma."

There are many different times and places in the life cycle of a lymphocyte where things can go wrong. Depending on when and how the lymphocyte goes bad determine the particular type and grade of lymphoma. Just how wide spread the bad lymphocytes go determines the stage. If they hang around the local candy store (oops, I mean a single lymph node) then it is called stage one. If instead they rampage throughout the city (body), getting into all different kinds of places, then it might be called stage IV.

Even in lymphoma patients, most lymphocytes are good citizens, doing their job quietly, having kids when necessary, etc. The other kinds of white blood cells are also normal. It's just this one criminal family that's causing all the problems.

If this lymphoma mob is aggressive and keeps growing, then you can send out the cops (chemotherapy, radiation) to arrest (shoot on sight, actually) any lymphocyte acting aggressively. Unfortunately, any other cells that are growing quickly at the same time are subject to the same martial law. This is what causes side effects.

If the mob is indolent (lazy) they can't be identified as readily and the cops can't wipe all of them out. But they can do a good job of keeping them in check for many years.

Sometimes mobster lymphocytes sneak into the nursery (bone marrow) where newborn blood cells grow to maturity. This makes it easier for the mobsters evil kin to spread. (Bone marrow involvement)

Sometimes, with an aggressive mob, the cops just can't handle it. Then it's time to call out the military. They just kill everyone in the city (high dose chemotherapy.) Unfortunately this also wipes out the nursery. Fortunately, before they bomb the place, they save enough newborns (stem cells) to repopulate the nursery and go forth into the now empty city. If they can't get enough healthy babies from the city (the body) the powers that be find some other city (bone marrow donor) and take some of their baby cells to repopulate after the high-dose chemo. (This is called a stem cell rescue or bone marrow transplant.)

After this, the city is left with some damage, but often continues normally from then on.

I think I've confused myself enough at this point, so I'll quit for now. 

© 1999 Robert Scott Pallack

The Lymphatic System
The Lymphatic System is used to help to defend the body against invasion by disease causing agents. It includes a network of vessels that assists in circulating the body fluids. These vessels transport excess fluid away from the interstitial spaces and return it to the bloodstream.

Lymphatic Capillaries
Lymphatic Capillaries are microscopic, closed ended tubes. The extend into the spaces within most tissues, forming complex networks that parallel the networks of the blood capillaries. The walls of the lymphatic capillaries, like those of the blood capillaries, consists of a single layer of squamous epithelial cells. Fluids enter the lymphatic capillaries. Once the fluid does this a lymph is formed.

Lymphatic Vessels
The Lymphatic Vessels prevent backflow of lymph. They have specialized organs called lymph nodes. These nodes are vital in the defense against invasion of microorganisms.

Formation of a Lymph
When the osmotic pressure of the tissue rise, it interferes with the osmotic reabsorption of water by the blood capillaries. When the interstitial pressure increases the tissue fluid is forced into the lymphatic capillaries where it becomes a lymph. This lymph is responsible for transporting foreign particles to the lymph nodes.

Once a viral cell has entered the body the immune system is called on the help the body to fight against the viral cells destroying the T-cells. Usually a virus is embedded in the lipid bilayer of the plasma membrane.

T-Cells attack antigens or antigen-bearing agents directly, providing cell mediated immunity.

B-Cells produce antibodies that act against specific antigens, allowing for antibody-mediated immunity

Antibodies are composed of soluble proteins called immunoglobulins. Three most abundant types:IgG IgA Igm

The Thymus is a soft bilobed structure whose lobes are surrounded by connective tissue. It is located in front of the aorta and behind the upper part of the sternum. It can be subdivided into lobules which contain a large number of lymphocytes. The majority of these thymocytes remain inactive, but some develop into T-lymphocytes. They leave the thymus to provide for immunity. Also the thymus may secrete a hormone called thymosin which is believed to stimulate the activity of lymphocytes to migrate to other lymphatic tissues. This is the region where T-Cells are created.

The spleen resembles a large lymph node. It acts as a blood reservoir. Also the spleen contains numerous macrophages, which filter foreign particles and damaged red blood cells from the blood.