February 8th, 2010
is this correct?: rituxan KILLS off the lymphocytes that produce antibodies whereas immunosuppressive drugs merely SUPPRESS lymphocyte activity to prevent production of antibodies.
also, is the steroid prednisone considered an immunosuppressive drug?
Rituxan is a type of immunosuppressive drug; these drugs have a lot of different ways they suppress the immune system. Rituxan’s specific mechanism of action is to bind to the CD20 receptor on B-lymphocytes which eventually leads to the cell’s death. So Rituxan is targeted to B-cells (a type of lymphocyte)–and yes, it does kill off the lymphocytes that produce antibodies.
Here is more detailed information from Lexi-comp online:
Rituximab is a monoclonal antibody directed against the CD20 antigen on B-lymphocytes. CD20 regulates cell cycle initiation; and, possibly, functions as a calcium channel. Rituximab binds to the antigen on the cell surface, activating complement-dependent B-cell cytotoxicity; and to human Fc receptors, mediating cell killing through an antibody-dependent cellular toxicity. B-cells are believed to play a role in the development and progression of rheumatoid arthritis. Signs and symptoms of RA are reduced by targeting B-cells and the progression of structural damage is delayed.
Prednisone is considered an immunosuppressive drug; it actually belongs to a class of drugs called corticosteroids, and the way these drugs work their many effects is by suppressing the immune system.
Here is more detailed information on this from Lexi-comp:
prednisone decreases inflammation by suppression of migration of polymorphonuclear leukocytes and reversal of increased capillary permeability; suppresses the immune system by reducing activity and volume of the lymphatic system; suppresses adrenal function at high doses. Antitumor effects may be related to inhibition of glucose transport, phosphorylation, or induction of cell death in immature lymphocytes.
Actually, in reading this (last sentence specifically)–it looks like they’re saying predinsone may actually have some cytotoxic (cell-killing) activity–I didn’t know that.
More than likely, if you’re talking about a immunosuppressive drug, it generally does just suppress the immune system, and doesn’t kill off anything. For example, another monoclonal antibody (like rituximab) is basiliximab; this one works in this way: "Chimeric (murine/human) monoclonal antibody which blocks the alpha-chain of the interleukin-2 (IL-2) receptor complex; this receptor is expressed on activated T lymphocytes and is a critical pathway for activating cell-mediated allograft rejection."
That’s from Lexi-comp of course because I didn’t quite remember how it worked off-hand. But as you can see, this one blocks interleukin-2 which is part of the pathway that enhances the action of the immune system. By blocking this, the immune system is *suppressed*–thus the term "immunosuppressive drugs". Cellcept belongs to another class of drugs that are immunosuppressives (and not cytotoxic–just cytostatic). There are a great many ways immunosuppressive drugs work, those are just a few examples. Hope all this helped some!
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