Immunologic reconstitution of foals with combined immunodeficiency.

Thirty-eight foals with combined immunodeficiency (CID) received transplanted fetal liver cells, fetal liver and thymus cells, histocompatible bone marrow cells, or equine lymphocyte antigen (ELA) haploidentical bone marrow cells in an attempt to reconstitute their deficient immune systems. Engraftment was infrequent, partial, and unpredictable when fetal cells were employed. Three of five CID foals receiving ELA haploidentical bone marrow cells demonstrated partial reconstitution, but engraftment was only temporary. Administration of histocompatible bone marrow cells resulted in rapid, full and sustained engraftment.

Correction of equine severe combined immunodeficiency by bone marrow transplantation.

A 32-day-old horse with severe combined immunodeficiency was transplanted with equine bone marrow cells in an attempt to establish immunologic responsiveness. A histocompatible, mixed-leukocyte-culture-nonreactive, sex-matched, full sibling was used as the donor. Recipient total lymphocyte count, T and B lymphocyte numbers, and response of peripheral blood mononuclear cells to phytolectin stimulation increased by 14 days following transplantation. Circulating lymphocytes exceeded 1000 cells/microliter blood by 40 days posttransplantation, and by 170 days following transplantation, T and B lymphocyte numbers had reached normal values. The foal demonstrated significant primary and secondary antibody responses when immunized with bacteriophage phi X 174 at 100 and 142 days posttransplantation. Concentrations of IgG and IgM remained within the normal range following cessation of i.v. plasma therapy 156 days after transplantation. More than 300 days following transplantation, the foal remains healthy and is growing normally. At no time during the posttransplant period was there detectable evidence of graft-versus-host disease.