In vivo T cell depletion in miniature swine using the swine CD3 immunotoxin, pCD3-CRM9.
BACKGROUND
Partially inbred miniature swine developed in this laboratory provide a unique preclinical large animal model for studying transplant tolerance. The importance of in vivo T cell depletion for establishing stable mixed hematopoietic cell chimerism using a clinically relevant sublethal regimen has been well documented in murine studies (1). Until now, the lack of an effective in vivo T cell-depleting reagent in swine has limited the progress of studies involving hematopoietic cell transplants.


METHODS
The swine CD3 immunotoxin, pCD3-CRM9, was prepared by conjugating our porcine-specific CD3 monoclonal antibody 898H2-6-15 to the diphtheria toxin derivative, CRM9. The resultant immunotoxin was administered i.v. to several miniature swine at doses ranging from 0.15-0.2 mg/kg either in a single dose or two doses 2 days apart. T-cell depletion was monitored in the peripheral blood, mesenteric lymph node, and thymus by flow cytometric analysis and histological examination.


RESULTS
T cells were depleted to less than 1% of their pretreatment levels based on absolute numbers in the peripheral blood. Fluorescence activated cell sorter analysis and histological examination of serial lymph node biopsies confirmed depletion of the CD3+ T cells rather than down modulation or masking of the surface CD3 expression. Depletion of the CD3 bright medullary thymocytes could also be detected by flow cytometry and histological examination after immunotoxin treatment.


CONCLUSIONS
Administration of the immunotoxin i.v. drastically depletes mature T cells from the peripheral blood, lymph node, and thymus compartments of the pig. This first description of an effective in vivo T-cell depleting reagent for the pig provides a valuable tool for studies of transplant tolerance in this large animal model. It also makes possible preclinical studies of T cell depletion with anti-CD3 immunotoxin in this large animal model.
Huang
C A
CA
Transplantation Biology Research Center, Department of Pathology, Massachusetts General Hospital/Harvard Medical School, Boston 02129, USA.
Yamada
K
K
Murphy
M C
MC
Shimizu
A
A
Colvin
R B
RB
Neville
D M
DM
Sachs
D H
DH
D000818:Animals; D001426:Bacterial Proteins / Q000276:immunology* / Q000633:toxicity; D001769:Blood / Q000276:immunology; D017252:CD3 Complex / Q000276:immunology* / Q000633:toxicity; D004167:Diphtheria Toxin / Q000276:immunology; D000922:Immunotoxins / Q000008:administration & dosage; D008198:Lymph Nodes / Q000276:immunology; D008212:Lymphocyte Depletion; D010523:Peripheral Nervous System Diseases / Q000139:chemically induced; D013552:Swine; D013556:Swine, Miniature; D013601:T-Lymphocytes / Q000276:immunology*; D013950:Thymus Gland / Q000276:immunology
D001426:Bacterial Proteins; D017252:CD3 Complex; C053395:CRM9 protein, bacteria; D004167:Diphtheria Toxin; D000922:Immunotoxins