Immunosuppression explained

I posted this in another section, General Questions/MGUS, in reply to blskat1. I’m repeating it here because I thought this might be of general interest.

I don’t know why I didn’t think about this before but I pulled out my textbook, [I]Immunology[/I] by Klaus Elgert. There are several pages on the topic of immunosuppression which I never studied before, probably more than either one of us care to know. I will try to summarize the important sections.

There are three methods:

[B]1. Physical methods[/B], i.e. removing the immune systems cells and tissues, surgery etc.
[B]2. Chemical methods[/B] (more about this below)
[B]3. Biological methods[/B] such as using antigen or antibodies. The exact mechanism of action for biological immunosuppressive agents is not thoroughly known. IVIG and Rituxan belong here (my comment)

[B]Chemical immunosuppressants[/B] can be placed in four main groups: corticosteroids, alkylating agents, anti-metabolites, and antibiotics.

[B]Steroids:[/B] in humans the immunosuppressive effects of steroids are poorly defined. [I]Cortisone[/I] for example mediates lysis of susceptible lymphocytes and anti-inflammatory actions. They cause the cell nucleus to disintegrate and cells to lose their cytoplasm. Unlike other immunosuppressants, they are effective whether or not cells are in their replicative cycle.

[B]Alkylating agents[/B]: these interfere with some basic metabolic processes needed for cell division, differentiation or protein synthesis. The main effect is on DNA synthesis by adding alkyl chemical groups to nucleic acids and proteins. They destroy lymphocytes and reduce proliferation. Well-known drugs are [I]Cyclophosphamide [/I](Cytoxin) and [I]Chlorambucil[/I].

[B]Anti-metabolic agents:[/B] they also interfere with basic metabolic processes[B],[/B] primarily inhibiting cell division. They function as antagonist of folic acid as well as purines or pyrimidines. All these are essential for DNA synthesis. They resemble natural molecules but lead to faulty cell metabolism. Of interest for us, of course, would be the inhibiting effect on T and B-cell proliferation.[I] Imuran[/I] would be one of these drugs.

[B]Antibiotic agents[/B]: some of them have immunosuppressive activity. One example is [I]Cyclosporin A[/I]. It differs from other immunosuppressive drugs because it is not lymphocytic and has selectivity. Its principal target is the Th(helper T) cell. It suppresses T-cell growth and differentiation without directly affecting antibody production or impair marrow function.