THE FATE OF HUMAN PERIPHERAL-BLOOD LYMPHOCYTES AFTER TRANSPLANTATION INTO SCID MICE

Human peripheral blood lymphocytes (hu-PBL) can be adoptively transfer red by intraperitoneal injection into mice with severe combined immuno deficiency (SCID). The transplanted lymphocytes can produce immunoglob ulin (Ig), respond to antigens, and survive for months in this chimeri c model (hu-PBL SCID). However, whether the lymphocytes actually repop ulate and reconstitute lymphoid structures and organs has been subject of some debate. To address this question and to characterize the hu-P BL SCID model better, we employed a novel technique for the identifica tion of human cells in xenogeneic mice.We used fluorescence in situ hy bridization (FISH) with a biotinylated DNA probe to all human centrome res.We demonstrated that FISH could be used to detect human cells when they accounted for less than 1 % of human/mouse cell mixtures; it cou ld also be employed for the identification and localization of individ ual human cells in tissue sections. By using FISH, we studied 31 SCID mice injected with 1.5 x 10(7) - 4 x 10(7) hu-PBL via intravenous (iv. ) or intraperitoneal (i.p.) routes. In the 6 iv.-injected mice, we fou nd that the human cells were removed from the circulation into the lun g within 1 h. In 22 of 25 i.p.-injected animals, 90-3716 mug/ml of hum an IgG was found in the sera at 3 to 13 weeks after transplantation (a .t.). Human cells colonized the peritoneal cavity and persisted for up to 13 weeks a.t. and, in the 12 mice studied, accounted for 4 % to 57 % of the cells in the peritoneal fluid. However, only rare, isolated human cells were found in the spleen, blood, bone marrow, lung or Peye r's patches. In 7 of 19 mice that received hu-PBL i.p. from Epstein-Ba rr virus-seropositive donors, we found masses of human cells usually b eneath the peritoneal lining but sometimes infiltrating normal tissue. We conclude that FISH offers a simple means for accurate identificati on of human cells in the xenogeneic mouse. Although there is colonizat ion of the peritoneal cavity in most mice, and development of lymphoid masses in some, there is no reconstitution of lymphoid structures and only minimal engraftment of lymphoid organs by human cells in convent ionally-prepared hu-PBL SCID constructs.