 Blood samples are collected at baseline and on days 30, 60, and 100 for correlative laboratory studies. Samples are analyzed for killer immunoglobulin-like receptor KIR mismatches by genotyping and immunophenotyping methods PCR and flow cytometry; natural killer NK cell reconstitution by flow cytometry; and NK cell function, NK cell allo-reactivity by ELISPOT and ELISA. 