Immunosuppressants Flashcards
what is autograft?
cells from the same person are put back on them in another location
what is allograft?
cells or tissue from a donor and giving them to another person to use
what is xenograft?
taking human tumour cells and putting them in mice (or another species)
what are the 3 stages of graft (organ) rejection?
hyperacute - in minutes
aute - 7-21 days
chronic - 3 months
what can cause organ rejection?
tissue have certain memories, and when they are placed in another individual and the tissues mesh but are not completely compatible, a reaction can occur
what is the major target for anti-rejection drugs?
T cell and B cell activation/clonal expansion, cytokine production, antibody action
what is the process that leads to organ rejection?
foreign organ proteins bind to antigens on macrophages
stimulate T cell response
T cells help mediate B cell response by releasing cytokines(make antibodies)
antibodies mediate antibody response (neutralization, opsonization, phagocytosis), leading to organ rejection
describe the process of antibody formation
1) antigen binds to antigen receptor on activated B cell
2) proliferation occurs
3) further proliferation and differentiation into two types of cells
4) plasma cells mediate antibody response
5) memory cells contain antibody memory aspect and knows if youve been exposed to the allergen before
what are anti-rejection drugs
drugs that act on the induction phase (B cell activation via T cells and proliferation) of immune response or that target the effector phase of immune response (differentiation/synthesis of B cells leading to tissue injury)
what are two categories of anti-rejection drugs targeting induction phase? give examples for each
inhibitors of interleukin-2 production (cyclosporine, tacrolimus)
inhibitor of cytokine gene expression (glucocorticoids)
both IL and cytokines are major factors that help activate B and T cells
what is cyclosporine?
a fat soluble cyclic peptide with 11 amino acids derived from fungus Tolypocladium inflatum and is used in the treatment of organ transplant (kidney, heart, bone marrow)
what is a benefit of cyclosporine?
low doses can be used in autoimmune diseases such as RA
What is the moa for cyclosporine?
cyclosporine binds to cytosolic protein cyclophilin (immunophilin) and form a complex which inhibits calcineurin/NF-AT activation and blocks IL-2 gene transcription - decr. T cell activation
briefly describe the PK for cyclosporine
Oral or IV admin oral admin has slow and incomplete absorption metabolism occurs in both GI and liver t1/2 = 24h concentrated in peripheral tissue
what are some side effects of cyclosporine?
nephrotoxicity** hypertension increased risk of infection liver dysfunction others: hyperglycemia, anorexia, lethargy, hirsutism, tremor, paraesthesia, gum hypertrophy, GI upset
what are some drug interactions with cyclosporine? which inhibits its metabolism and which induce it?
inhibit: CCBs antifungals - ketoconazole, fluconazole antibacterial agents - erythromycin, clarithromycin grapefruit juice induce: anticonvulsants - phenytoin antituberculosis agents - isoniazid, rifampin
what is tacrolimus?
a macrolide antibiotic produced by Streptomyces tsukubaenis with an moa similar to cyclosporine and used to prevent organ transplant rejection
how does the moa of tacrolimus differ from cyclosporine?
it binds to immunophilin FK binding protien (FKBP) which inhibits calcineurin phosphatase - leading to decreased activation of transcription factor NF-AT and decreased IL-2 gene transcription
briefly describe the PK for tacrolimus
oral or IV admin
t1/2 = 9-12h
metabolized by the liver
toxic effects similar to cyclosporine
what are 5 categories of anti-rejection drugs targeting effector phase? give examples of each
1) inhibit action of IL-2 (sirolimus)
2) inhibitors of purine synthesis (myclophenolate mofetil, azathioprine)
3) alkylating cytotoxic agents (cyclophosphamide)
4) suppressor of immune response (glucocorticoids)
5) immunosuppressive antibodies (polyclonal or monoclonal antibodies)
what is sirolimus?
a new macrolide antibiotic derived from Streptomyces hygroscopicus
what is the moa for sirolimus?
binds to intracellular immunophilins but does NOT block IL-2 gene transcription
interferes with IL-2 signal transduction pathway in activated T cells resulting in deceased clonal proliferation of T cells and B cells
what is mycophenolate mofetil?
an agent that is converted to mycophenolic acid
selectively inhibits proliferation of both T and B lymphocytes and cytotoxic T cells
what is the moa for mycophenolate mofetil?
potent inhibitor of inosine 5’-monophosphate dehydrogenase, a crucial enzyme in purine synthesis
T cells and B cells are particularly dependent on this pathway for proliferation
briefly describe the PK for mycophenolate mofetil
oral admin (well absorbed)
Mg and Al impair absorption
metabolite mycophenolic acid and glucoronide conjugate undergo enterohepatic circulation
eliminated by kidney as inactive glucoronide
what does azathioprine do?
it is metabolized to 6-mercaptopurine which is a purine antimetabolite
interferes with purine synthesis (inhibits HGPRT enzyme, which catalyzes conversion of purine base to purine ribosyl monophosphate) and is cytotoxic in dividing cells
results in inhibition of clonal T and B cell proliferation
inhibits both cell mediated and antibody mediated immune reactions
what is a major side effect for azathioprine?
bone marrow depression
what is cyclophosphamide? how does it work?
a nitrogen mustard (alkylating agent)
inactive until metabolized by liver into active phosphoramide mustard
alkyl groups cross react with two DNA nucleophilic sites (intra/inter guanine) and inhibit DNA replication, leading to cell death