Cord blood (CB) hematopoietic stem cell transplantation can be successful even if donor and recipient are not fully matched for human leukocyte antigens (HLA). This may result from toleranceinducing events during pregnancy but to date this concept has not been tested in CB transplantation. Hence we analyzed the impact of fetal exposure to noninherited maternal antigens (NIMA) of the HLA-A, -B antigens, or -DRB1 alleles on the outcome of CB transplants. The 1,121 patients studied were transplanted for hematological malignancy with a single CB unit: 1,059 received grafts mismatched for one or two HLA antigens. Of these patients, 79 patients had a mismatched antigen that was identical to a donor NIMA, 25 with one HLA mismatch (MM), and 54 with two. If there was a NIMA match, transplant-related mortality (TRM) was improved, especially in patients >10 years (P ‫؍‬ 0.012) as were overall mortality and treatment failure (P ‫؍‬ 0.022 and 0.020, respectively, in the older subset), perhaps related to improved neutrophil recovery, especially in patients who received a low total nucleated cell (TNC) dose (P ‫؍‬ 0.031). Posttransplant relapse rate also tended to be reduced, especially in patients with myelogenous malignancies given units with a single HLA mismatch (P ‫؍‬ 0.074). These findings represent unique evidence that donor exposure to NIMA can improve survival in unrelated CB transplantation and might reduce relapse, indicating that cord blood cells can mount an antileukemic effect. By matching for donor NIMAs in search algorithms of CB inventories, the probability of selecting a graft with an optimal outcome will increase significantly.cord blood transplantation ͉ hematopoietic stem cell transplantation ͉ relapse reducing mechanisms ͉ tolerance

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The data summarized herein demonstrate the utility of the low-affinity Fc epsilon R in delineating murine B-cell subsets. In the peritoneal cavity, the Fc epsilon R appears to be a reliable marker in distinguishing between conventional (Fc epsilon R+) and Ly-1/sister (Fc epsilon R-) B cells. In the spleens of normal animals, flow cytometric and histologic studies established that a distinct population of Fc epsilon R- B cells is also present and comprises the marginal zones. Thus in the spleen, the Fc epsilon R may be the first murine marker to allow for selective purification and analysis of marginal zone B cells. Although it is unlikely that splenic Fc epsilon R- B cells are directly related to peritoneal Fc epsilon R- Ly-1/sister B cells, further studies will be required to address this question. Analysis of autoimmune mice revealed that the splenic Fc epsilon R- subset is greatly expanded in these animals and indicates that the Fc epsilon R may be a sensitive indicator of abnormalities within the B-cell compartment. Additional studies compared the functional capacity of Fc epsilon R+ and Fc epsilon R- B cells and tested the ability of these populations to isotype-switch and respond to polyclonal stimuli. The results showed that Fc epsilon R+ and Fc epsilon R- B cells from both the peritoneum and spleen can switch to produce IgG, and all but the peritoneal Fc epsilon R- B cells can switch to the IgE class. This latter result is certainly interesting and demonstrates an important functional difference between peritoneal and splenic Fc epsilon R- B cells. Finally, experiments with B-cell mitogens showed further differences between the Fc epsilon R+ and Fc epsilon R- subsets. Whereas Fc epsilon R- B cells appeared to be more sensitive to LPS stimulation, Fc epsilon R+ B cells were clearly more responsive to an anti-IgM signal. Taken together, the results show that the Fc epsilon R is likely to be useful in separating B cells with different phenotypic, histologic, and functional characteristics.

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