title: Immunomodulatory effects of combination of pooled human gammaglobulin and rapamycin on cell proliferation and apoptosis in the mixed lymphocyte reaction.
abstract: BACKGROUND
  Multidrug immunosuppressive regimens benefit transplant recipients, reducing side effects and creating synergy between medications with different mechanisms of action. We have shown that pooled human gammaglobulin (intravenous immunoglobulin [IVIG]) inhibits the mixed lymphocyte reaction (MLR) and induces apoptosis primarily in B cells. Rapamycin (RAPA), a potent macrolide immunosuppressant, inhibits B- and T-cell proliferation through G1 cell-cycle blockade and purportedly induces apoptosis. Here we examined the possible synergistic effects of IVIG and RAPA on cell proliferation and apoptosis induction in the MLR.
  
  
  METHODS
  MLR was performed with IVIG (0.2-5 mg/mL), RAPA (0.02-40 ng/mL), alone or in combination. Cell proliferation was detected by H-thymidine incorporation, and apoptosis by Annexin V and terminal deoxynucleotide transferase-mediated dUTP nick-end labeling flow cytometry.
  
  
  RESULTS
  IVIG or RAPA inhibited cell proliferation in a dose-dependent manner. RAPA (0.02-40 ng/mL) in combination with IVIG (5 mg/mL) significantly augmented the inhibition compared with RAPA alone (70% vs. 34% at 0.2 ng/mL; 90% vs. 76% at 2 ng/mL). Apoptosis was significantly higher in IVIG-treated (5 mg/mL) CD19+ cells and less so in CD3+ cells. However, RAPA (0.2-40 ng/mL) neither induced apoptosis nor altered apoptosis induced by IVIG.
  
  
  CONCLUSIONS
  Combined RAPA and IVIG at subtherapeutic concentrations inhibits cell proliferation in the MLR. RAPA neither induces apoptosis nor augments apoptosis induced by IVIG in the MLR. Lower-concentration RAPA (0.2-2 ng/mL) in combination with IVIG (5 mg/mL) versus therapeutic levels (2-50 ng/mL and 10-40 mg/mL, respectively) could represent an effective immunomodulatory drug combination.
authors.affiliation: Transplant Immunology Laboratory, Ahmanson Pediatric Center, Steven Spielberg Pediatric Research Laboratories, Cedars-Sinai Medical Center/UCLA School of Medicine, 8700 Beverly Boulevard, Los Angeles, CA 90048, USA. Mieko.Toyoda@cshs.org
authors.forename: Mieko
authors.initials: M
authors.lastname: Toyoda
authors.forename: Anna
authors.initials: A
authors.lastname: Petrosyan
authors.forename: Andy
authors.initials: A
authors.lastname: Pao
authors.forename: Stanley C
authors.initials: SC
authors.lastname: Jordan
mesh_terms: D000328:Adult; D017209:Apoptosis / Q000187:drug effects*; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D006801:Humans; D007107:Immune System / Q000187:drug effects*; D016756:Immunoglobulins, Intravenous / Q000008:administration & dosage / Q000494:pharmacology*; D007166:Immunosuppressive Agents / Q000008:administration & dosage / Q000494:pharmacology*; D007959:Lymphocyte Culture Test, Mixed; D009000:Monocytes / Q000166:cytology / Q000187:drug effects* / Q000276:immunology / Q000502:physiology; D020123:Sirolimus / Q000008:administration & dosage / Q000494:pharmacology*
chemical_list: D016756:Immunoglobulins, Intravenous; D007166:Immunosuppressive Agents; D020123:Sirolimus