UWorld step 1 immunology Question Id: 18706

The card doesn't explain to you why and how mycophenolate does this, making it harder to recall and use the information when you need it.

Question explanation quoted:
"Mycophenolate is an immunosuppression drug used to prevent organ transplant rejection. lt functions via the inhibition of inosine 5'-monophosphate
dehydrogenase (IMPDH), an enzyme in the de novo purine synthesis pathway. The utility of mycophenolate as an immunosuppressant is aided by its relatively
specific suppression of lymphocyte proliferation compared with other hematopoietic cell lines (eg, neutrophils, erythrocytes). This relative lymphocyte specificity is
driven by 2 factors:
1.Activated lymphocytes have a nearly absent purine salvage pathway and therefore are mostly dependent on de novo purine synthesis. Other hematopoietic cell lines have a more robust purine salvage pathway and can better compensate for inhibition of the de novo pathway.
2.There are 2 subtypes of the llleDH enzyme: Lymphocytes primarily contain type 2 IMPDH, whereas other cell lines contain a greater proportion of type 1.
Mycophenolate binds to and inhibits type 2 IMPDH with a higher affinity than type 1.

Common adverse effects of mycophenolate include lymphopenia and gastrointestinal disturbances (eg, diarrhea).

(Choice A) Azathioprine produces active metabolites that inhibit an enzyme in the de novo purine synthesis pathway and also act as false nucleotides that
incorporate into and disrupt DNA and RNA. Both the de novo and salvage purine synthesis pathways are disrupted, resulting in relatively nonspecific hematopoietic
suppression.
(Choice C) Prednisone and other glucocorticoids inhibit NF—kB to decrease the transcription of lL—2 and many other cytokines. These drugs have wide-ranging
effects that suppress the function of all leukocyte cell lines.
(Choice D) Sirolimus inhibits the mammalian target of rapamycin (mTOR) to interrupt lL—2 signal transduction and provide relatively specific lymphocyte suppression.
(Choice E) Tacrolimus and cyclosporine inhibit calcineurin to block transcription of lL—2. These drugs provide relatively specific lymphocyte suppression and are the
mainstay of therapy for preventing organ transplant rejection.

Educational objective:
Mycophenolate is an immunosuppression drug that inhibits inosine 5'—monophosphate dehydrogenase in the de novo purine synthesis pathway. It provides relatively
specific suppression of lymphocyte proliferation, largely because activated lymphocytes lack an established purine salvage pathway that is present in other
hematopoietic cell lines."

Resubmit and reword so that change is not verbatim from UWorld