HUMAN AND NONHUMAN PRIMATE LYMPHOCYTES ENGRAFTED INTO SCID MICE RESIDE IN UNIQUE MESENTERIC LYMPHOID STRUCTURES

The present study compares the location and phenotype of B lineage lym phocytes in tissues from SCID mice engrafted with PBMC of human, chimp anzee, and pig-tailed macaque origin. In mice repopulated with: both h uman and nonhuman primate lymphocytes, plasma cells were found in the peritoneal cavity in vascularized structures located in the mesentery near the pancreas, intestines, and spleen. The predominant isotype of the plasma cells was IgG; IgM and IgA cells were also present, kappa a nd lambda light chains were expressed by 62% and 38% of the Ig-contain ing cells, respectively. J chain expression occurred in most cells irr espective of the Ig isotype. In the SCID mice engrafted with human lym phocytes, a few IgM-containing cells were found in the spleen; plasma cells were not found in other tissues, including the intestine, The ag gregation of plasma cells did not appear to be a result of infection w ith EBV, T cells were rarely found in the lymphoid aggregates but were recovered from the spleen and peritoneal lavage. Human Ig levels in t he serum of engrafted mice reflected the isotype distribution of the c ells with IgG > IgM greater than or equal to IgA.