DEMONSTRATION OF EQUINE IMMUNOGLOBULIN IN SERA FROM SEVERE COMBINED IMMUNODEFICIENCY BEIGE MICE INOCULATED WITH EQUINE LYMPHOCYTES

Peripheral blood lymphocytes were isolated from four normal adult hors es on Ficoll-Hypaque density gradients for intraperitoneal inoculation into 16 C.B-17 severe combined immunodeficiency/beige mice in an atte mpt to create a xenogeneic lymphoid chimera for modeling the equine im mune system. The recipient mice had been preconditioned by prior expos ure to 200 cGy of gamma irradiation. The mice were monitored for the p resence of equine IgG using an ELISA technique. Equine IgG was detecte d in the sera of 91.7% of murine recipients and in at least one mouse inoculated from each donor horse. The levels of IgG detected in the mi ce ranged from 2 mu g ml(-1) to over 1000 mu g ml(-1) and showed stead y decline from the time of inoculation to the end of the trial. The ha lf-life of equine IgG in the SCID/beige mouse was determined to be 12. 1 days by the intravenous injection of 9.1 mg of semi-purified equina IgG into 21 normal SCID/beige mice and taking serial blood samples to obtain the decay curve. The half-life of equine IgG was compared with the extinction curve obtained for the engrafted mice and showed that c ontinuous production within the mice must have been occurring since th e slopes of the two lines were different. These results are compared w ith those achieved in equine PBL-SCID/beige chimeras not preconditione d by irradiation and to those achieved in human and bovine PBL-SCTD ch imeras.