ENGRAFTMENT AND HUMORAL IMMUNITY IN SCID AND RAG-2-DEFICIENT MICE TRANSPLANTED WITH HUMAN PERIPHERAL-BLOOD LYMPHOCYTES

SCID and RAG-2 deficient mice were transplanted intraperitoneally with human peripheral blood lymphocytes (hu-PBL-SCID and hu-PBL-RAG mice). Seven days after transplantation the mice were immunized with a pneum ococcal polysaccharide vaccine. Flow cytometry analysis of cells from the peritoneal cavity and the spleen after 8-10 weeks revealed that hu man cells had more limited engraftment in RAG than in SCID recipient m ice, and that more human cells were found in the spleen than in the pe ritoneal cavity. Functionality of the human cells recovered from these two locations was explored by the counting of human immunoglobulin se creting cells (hu-ISC). A total of 83% of the hu-PBL-SCID mice and 29% of the hu-PBL-RAG mice had detectable hu-ISC in the peritoneal cavity and/or the spleen. The kinetic profiles of human immunoglobulins in t he mouse sera during the experiment showed donor dependency. More than 90% of the hu-PBL-SCID mice had detectable levels of human IgG, IgM a nd IgA, while 78% had detectable levels of IgE, whereas detectable lev els of ISC, IgM, IgA and IgE were measured in 37%, 64%, 68% and 23% of the hu-PBL-RAG mice, respectively. Forty-seven per cent of immunized hu-PBL-SCID mice showed a human antipneumococcal IgG level that was si gnificantly above the background level in non-immunized mice, while no ne of the hu-PBL-RAG mice produced any detectable levels of human anti pneumococcal IgG. In short, human PBL showed a better engraftment and a better antibody response when transplanted into SCID mice than into RAG mice.