Clearance of mobilized porcine peripheral blood progenitor cells is delayed by depletion of the phagocytic reticuloendothelial system in baboons

Murali Basker, Ian P J Alwayn, Leo Buhler, David Harper, Sonny Abraham, Huw S Kruger Gray, Holly DeAngelis, Michel Awwad, Julian Down, Robert Rieben, Mary E. White-Scharf, David H. Sachs, Aron Thall, David K C Cooper

Research output: Contribution to journalArticle

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Abstract

Introduction. Attempts to achieve immunological tolerance to porcine tissues in nonhuman primates through establishment of mixed hematopoietic chimerism are hindered by the rapid clearance of mobilized porcine leukocytes, containing progenitor cells (pPBPCs), from the circulation. Eighteen hours after infusing 1-2 ×1010 pPBPC/kg into baboons that had been depleted of circulating anti-αGal and complement, these cells are almost undetectable by flow cytometry. The aim of the present study was to identify mechanisms that contribute to rapid clearance of pPBPCs in the baboon. This was achieved by depleting, or blocking the Fc-receptors of, cells of the phagocytic reticuloendothelial system (RES) using medronate liposomes (MLs) or intravenous immunoglobulin (IVIg), respectively. Methods. Baboons (preliminary studies, n=4) were used in a dose-finding and toxicity study to assess the effect of MLs on macrophage depletion in vivo. In another study, baboons (n=9) received a nonmyeloablative conditioning regimen (NMCR) aimed at inducing immunological tolerance, including splenectomy, whole body irradiation (300 cGy) or cyclophosphamide (80 mg/kg), thymic irradiation (700 cGy), T-cell depletion, complement depletion with cobra venom factor, mycophenolate mofetil, anti-CD154 monoclonal antibody, and multiple extracorporeal immunoadsorptions of anti-αGal antibodies. The baboons were divided into three groups: Group 1 (n=5) NMCR+pPBPC transplantation; Group 2 (n=2) NMCR+ML+pPBPC transplantation; and Group 3 (n=2) NMCR+IVIg+pPBPC transplantation. Detection of pig cells in the blood was assessed by fluorescence-activated cell sorter and polymerase chain reaction (PCR). Results. Preliminary studies: ML effectively depleted macrophages from the circulation in a dosedependent manner. Group 1: On average, 14% pig cells were detected 2 hr postinfusion of 1 × 1010 pPBPC/kg. After 18 hr, there were generally less than 1.5% pig cells detectable. Group 2: Substantially higher levels of pig cell chimerism (55-78%) were detected 2 hr postinfusion, even when a smaller number (0.5-1 × 1010/kg) of pPBPCs had been infused, and these levels were better sustained 18 hr later (10-52%). Group 3: In one baboon, 4.4% pig cells were detected 2 hr after infusion of 1 × 1010 pPBPC/kg. After 18 hr, however, 7.4% pig cells were detected. A second baboon died 2 hr after infusion of 4 × 1010 pPBPC/kg, with a total white blood cell count of 90,000, of which 70% were pig cells. No differences in microchimerism could be detected between the groups as determined by PCR. Conclusions. This is the first study to report an efficient decrease of phagocytic function by depletion of macrophages with MLs in a large-animal model. Depletion of macrophages with MLs led to initial higher chimerism and prolonged the survival of circulating pig cells in baboons. Blockade of macrophage function with IVIg had a more modest effect. Cells of the RES, therefore, play a major role in clearing pPBPCs from the circulation in baboons. Depletion or blockade of the RES may contribute to achieving mixed hematopoietic chimerism and induction of tolerance to a discordant xenograft.

Original languageEnglish (US)
Pages (from-to)1278-1285
Number of pages8
JournalTransplantation
Volume72
Issue number7
StatePublished - Oct 15 2001
Externally publishedYes

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Mononuclear Phagocyte System
Papio
Blood Cells
Swine
Stem Cells
Chimerism
Liposomes
Macrophages
Intravenous Immunoglobulins
Transplantation
Mycophenolic Acid
Polymerase Chain Reaction
Fc Receptors
Whole-Body Irradiation
Splenectomy
Phagocytes
Leukocyte Count
Heterografts
Cyclophosphamide
Primates

ASJC Scopus subject areas

  • Transplantation
  • Immunology

Cite this

Clearance of mobilized porcine peripheral blood progenitor cells is delayed by depletion of the phagocytic reticuloendothelial system in baboons. / Basker, Murali; Alwayn, Ian P J; Buhler, Leo; Harper, David; Abraham, Sonny; Kruger Gray, Huw S; DeAngelis, Holly; Awwad, Michel; Down, Julian; Rieben, Robert; White-Scharf, Mary E.; Sachs, David H.; Thall, Aron; Cooper, David K C.

In: Transplantation, Vol. 72, No. 7, 15.10.2001, p. 1278-1285.

Research output: Contribution to journalArticle

Basker, M, Alwayn, IPJ, Buhler, L, Harper, D, Abraham, S, Kruger Gray, HS, DeAngelis, H, Awwad, M, Down, J, Rieben, R, White-Scharf, ME, Sachs, DH, Thall, A & Cooper, DKC 2001, 'Clearance of mobilized porcine peripheral blood progenitor cells is delayed by depletion of the phagocytic reticuloendothelial system in baboons', Transplantation, vol. 72, no. 7, pp. 1278-1285.
Basker, Murali ; Alwayn, Ian P J ; Buhler, Leo ; Harper, David ; Abraham, Sonny ; Kruger Gray, Huw S ; DeAngelis, Holly ; Awwad, Michel ; Down, Julian ; Rieben, Robert ; White-Scharf, Mary E. ; Sachs, David H. ; Thall, Aron ; Cooper, David K C. / Clearance of mobilized porcine peripheral blood progenitor cells is delayed by depletion of the phagocytic reticuloendothelial system in baboons. In: Transplantation. 2001 ; Vol. 72, No. 7. pp. 1278-1285.
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abstract = "Introduction. Attempts to achieve immunological tolerance to porcine tissues in nonhuman primates through establishment of mixed hematopoietic chimerism are hindered by the rapid clearance of mobilized porcine leukocytes, containing progenitor cells (pPBPCs), from the circulation. Eighteen hours after infusing 1-2 ×1010 pPBPC/kg into baboons that had been depleted of circulating anti-αGal and complement, these cells are almost undetectable by flow cytometry. The aim of the present study was to identify mechanisms that contribute to rapid clearance of pPBPCs in the baboon. This was achieved by depleting, or blocking the Fc-receptors of, cells of the phagocytic reticuloendothelial system (RES) using medronate liposomes (MLs) or intravenous immunoglobulin (IVIg), respectively. Methods. Baboons (preliminary studies, n=4) were used in a dose-finding and toxicity study to assess the effect of MLs on macrophage depletion in vivo. In another study, baboons (n=9) received a nonmyeloablative conditioning regimen (NMCR) aimed at inducing immunological tolerance, including splenectomy, whole body irradiation (300 cGy) or cyclophosphamide (80 mg/kg), thymic irradiation (700 cGy), T-cell depletion, complement depletion with cobra venom factor, mycophenolate mofetil, anti-CD154 monoclonal antibody, and multiple extracorporeal immunoadsorptions of anti-αGal antibodies. The baboons were divided into three groups: Group 1 (n=5) NMCR+pPBPC transplantation; Group 2 (n=2) NMCR+ML+pPBPC transplantation; and Group 3 (n=2) NMCR+IVIg+pPBPC transplantation. Detection of pig cells in the blood was assessed by fluorescence-activated cell sorter and polymerase chain reaction (PCR). Results. Preliminary studies: ML effectively depleted macrophages from the circulation in a dosedependent manner. Group 1: On average, 14{\%} pig cells were detected 2 hr postinfusion of 1 × 1010 pPBPC/kg. After 18 hr, there were generally less than 1.5{\%} pig cells detectable. Group 2: Substantially higher levels of pig cell chimerism (55-78{\%}) were detected 2 hr postinfusion, even when a smaller number (0.5-1 × 1010/kg) of pPBPCs had been infused, and these levels were better sustained 18 hr later (10-52{\%}). Group 3: In one baboon, 4.4{\%} pig cells were detected 2 hr after infusion of 1 × 1010 pPBPC/kg. After 18 hr, however, 7.4{\%} pig cells were detected. A second baboon died 2 hr after infusion of 4 × 1010 pPBPC/kg, with a total white blood cell count of 90,000, of which 70{\%} were pig cells. No differences in microchimerism could be detected between the groups as determined by PCR. Conclusions. This is the first study to report an efficient decrease of phagocytic function by depletion of macrophages with MLs in a large-animal model. Depletion of macrophages with MLs led to initial higher chimerism and prolonged the survival of circulating pig cells in baboons. Blockade of macrophage function with IVIg had a more modest effect. Cells of the RES, therefore, play a major role in clearing pPBPCs from the circulation in baboons. Depletion or blockade of the RES may contribute to achieving mixed hematopoietic chimerism and induction of tolerance to a discordant xenograft.",
author = "Murali Basker and Alwayn, {Ian P J} and Leo Buhler and David Harper and Sonny Abraham and {Kruger Gray}, {Huw S} and Holly DeAngelis and Michel Awwad and Julian Down and Robert Rieben and White-Scharf, {Mary E.} and Sachs, {David H.} and Aron Thall and Cooper, {David K C}",
year = "2001",
month = "10",
day = "15",
language = "English (US)",
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pages = "1278--1285",
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TY - JOUR

T1 - Clearance of mobilized porcine peripheral blood progenitor cells is delayed by depletion of the phagocytic reticuloendothelial system in baboons

AU - Basker, Murali

AU - Alwayn, Ian P J

AU - Buhler, Leo

AU - Harper, David

AU - Abraham, Sonny

AU - Kruger Gray, Huw S

AU - DeAngelis, Holly

AU - Awwad, Michel

AU - Down, Julian

AU - Rieben, Robert

AU - White-Scharf, Mary E.

AU - Sachs, David H.

AU - Thall, Aron

AU - Cooper, David K C

PY - 2001/10/15

Y1 - 2001/10/15

N2 - Introduction. Attempts to achieve immunological tolerance to porcine tissues in nonhuman primates through establishment of mixed hematopoietic chimerism are hindered by the rapid clearance of mobilized porcine leukocytes, containing progenitor cells (pPBPCs), from the circulation. Eighteen hours after infusing 1-2 ×1010 pPBPC/kg into baboons that had been depleted of circulating anti-αGal and complement, these cells are almost undetectable by flow cytometry. The aim of the present study was to identify mechanisms that contribute to rapid clearance of pPBPCs in the baboon. This was achieved by depleting, or blocking the Fc-receptors of, cells of the phagocytic reticuloendothelial system (RES) using medronate liposomes (MLs) or intravenous immunoglobulin (IVIg), respectively. Methods. Baboons (preliminary studies, n=4) were used in a dose-finding and toxicity study to assess the effect of MLs on macrophage depletion in vivo. In another study, baboons (n=9) received a nonmyeloablative conditioning regimen (NMCR) aimed at inducing immunological tolerance, including splenectomy, whole body irradiation (300 cGy) or cyclophosphamide (80 mg/kg), thymic irradiation (700 cGy), T-cell depletion, complement depletion with cobra venom factor, mycophenolate mofetil, anti-CD154 monoclonal antibody, and multiple extracorporeal immunoadsorptions of anti-αGal antibodies. The baboons were divided into three groups: Group 1 (n=5) NMCR+pPBPC transplantation; Group 2 (n=2) NMCR+ML+pPBPC transplantation; and Group 3 (n=2) NMCR+IVIg+pPBPC transplantation. Detection of pig cells in the blood was assessed by fluorescence-activated cell sorter and polymerase chain reaction (PCR). Results. Preliminary studies: ML effectively depleted macrophages from the circulation in a dosedependent manner. Group 1: On average, 14% pig cells were detected 2 hr postinfusion of 1 × 1010 pPBPC/kg. After 18 hr, there were generally less than 1.5% pig cells detectable. Group 2: Substantially higher levels of pig cell chimerism (55-78%) were detected 2 hr postinfusion, even when a smaller number (0.5-1 × 1010/kg) of pPBPCs had been infused, and these levels were better sustained 18 hr later (10-52%). Group 3: In one baboon, 4.4% pig cells were detected 2 hr after infusion of 1 × 1010 pPBPC/kg. After 18 hr, however, 7.4% pig cells were detected. A second baboon died 2 hr after infusion of 4 × 1010 pPBPC/kg, with a total white blood cell count of 90,000, of which 70% were pig cells. No differences in microchimerism could be detected between the groups as determined by PCR. Conclusions. This is the first study to report an efficient decrease of phagocytic function by depletion of macrophages with MLs in a large-animal model. Depletion of macrophages with MLs led to initial higher chimerism and prolonged the survival of circulating pig cells in baboons. Blockade of macrophage function with IVIg had a more modest effect. Cells of the RES, therefore, play a major role in clearing pPBPCs from the circulation in baboons. Depletion or blockade of the RES may contribute to achieving mixed hematopoietic chimerism and induction of tolerance to a discordant xenograft.

AB - Introduction. Attempts to achieve immunological tolerance to porcine tissues in nonhuman primates through establishment of mixed hematopoietic chimerism are hindered by the rapid clearance of mobilized porcine leukocytes, containing progenitor cells (pPBPCs), from the circulation. Eighteen hours after infusing 1-2 ×1010 pPBPC/kg into baboons that had been depleted of circulating anti-αGal and complement, these cells are almost undetectable by flow cytometry. The aim of the present study was to identify mechanisms that contribute to rapid clearance of pPBPCs in the baboon. This was achieved by depleting, or blocking the Fc-receptors of, cells of the phagocytic reticuloendothelial system (RES) using medronate liposomes (MLs) or intravenous immunoglobulin (IVIg), respectively. Methods. Baboons (preliminary studies, n=4) were used in a dose-finding and toxicity study to assess the effect of MLs on macrophage depletion in vivo. In another study, baboons (n=9) received a nonmyeloablative conditioning regimen (NMCR) aimed at inducing immunological tolerance, including splenectomy, whole body irradiation (300 cGy) or cyclophosphamide (80 mg/kg), thymic irradiation (700 cGy), T-cell depletion, complement depletion with cobra venom factor, mycophenolate mofetil, anti-CD154 monoclonal antibody, and multiple extracorporeal immunoadsorptions of anti-αGal antibodies. The baboons were divided into three groups: Group 1 (n=5) NMCR+pPBPC transplantation; Group 2 (n=2) NMCR+ML+pPBPC transplantation; and Group 3 (n=2) NMCR+IVIg+pPBPC transplantation. Detection of pig cells in the blood was assessed by fluorescence-activated cell sorter and polymerase chain reaction (PCR). Results. Preliminary studies: ML effectively depleted macrophages from the circulation in a dosedependent manner. Group 1: On average, 14% pig cells were detected 2 hr postinfusion of 1 × 1010 pPBPC/kg. After 18 hr, there were generally less than 1.5% pig cells detectable. Group 2: Substantially higher levels of pig cell chimerism (55-78%) were detected 2 hr postinfusion, even when a smaller number (0.5-1 × 1010/kg) of pPBPCs had been infused, and these levels were better sustained 18 hr later (10-52%). Group 3: In one baboon, 4.4% pig cells were detected 2 hr after infusion of 1 × 1010 pPBPC/kg. After 18 hr, however, 7.4% pig cells were detected. A second baboon died 2 hr after infusion of 4 × 1010 pPBPC/kg, with a total white blood cell count of 90,000, of which 70% were pig cells. No differences in microchimerism could be detected between the groups as determined by PCR. Conclusions. This is the first study to report an efficient decrease of phagocytic function by depletion of macrophages with MLs in a large-animal model. Depletion of macrophages with MLs led to initial higher chimerism and prolonged the survival of circulating pig cells in baboons. Blockade of macrophage function with IVIg had a more modest effect. Cells of the RES, therefore, play a major role in clearing pPBPCs from the circulation in baboons. Depletion or blockade of the RES may contribute to achieving mixed hematopoietic chimerism and induction of tolerance to a discordant xenograft.

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