HUMAN PERIPHERAL-BLOOD LEUKOCYTE-RECONSTITUTED SEVERE COMBINED IMMUNODEFICIENT MOUSE - ANALYSIS OF THE HUMAN IMMUNE-RESPONSE AGAINST PORCINE ISLET TRANSPLANTATION

Human peripheral blood leukocyte (PBL)-reconstituted Severe combined i mmunodeficient (SCID) mice (Hu-PBL-SCID) were used as a model to study xenograft rejection in humans. SCID mice were reconstituted with huma n PBL using a protocol that included a booster injection with anti-hum an CD3 antibody-primed cells, This protocol enhanced chimera establish ment in SCID mice and resulted in the detection of higher levels of hu man Ig when compared with SCID mice receiving unprimed PBL alone. Huma n xenoreactive natural antibodies (XNA), both IgM and IgG subtypes, wh ich recognized porcine islets (PI), were detected in sera of Hu-PBL-SC ID by cytofluorometric analysis. Pretreatment of porcine cells with GS -IB4 lectin inhibited the XNA binding, demonstrating the specificity o f the XNA from Hu-PBL-SCID. Western blot analysis showed that XNA from normal human serum and Hu-PBL-SCID serum recognized similar xenoantig ens on PI, indicating that Hu-PBL-SCLD contained a XNA repertoire repr esentative of normal human serum. Immunofluorescent staining of the ti ssue sections revealed that both human IgG and IgM bound in vivo to th e PI engrafted beneath the kidney capsule of Hu-PBL-SCID. In addition, mouse complement (C3) was detected on xenografted PI. The function of xenografted islets were monitored by measuring porcine insulin concen tration using a radioimmunoassay, Porcine insulin concentration in the sera of both Hu-PBL-SCID and plain SCID xenografted with PI was simil ar for up to 14 days after transplantation, after which the insulin le vels in Hu-PBL-SCID decreased, thereby indicating rejection, Therefore , PI transplanted into the Hu-PBL-SCID should be a useful model for th e study of cellular as well as acquired humoral immune response agains t xenoislets.