NK cells are characterized by absence of CD3 but expression of CD56dim (90%, cytotoxic) and CD56brigh t (10%, mediator) (Shankaran et al Nature 2001). NK subsets carry out their respective functions based on their repertoire of NK receptors (NKRs) (Moretta et al Annu Rev Immunol 2001). Despite an immaturity in (spell out initials when first used) CB T-cell immunity, there is a similar leukemic relapse rate following UCBT vs. UBMT (Cairo et al Blood 1997). There is, however, a paucity of data comparing PB vs. CB NK subsets and NKR expression. In this study, we positively selected PB vs. CB CD56+ cells using magnetic beads (Miltenyi) and sorted into CD3-/CD56bright and CD3-/CD56dim and NKR expression measured (CD16, CD158a {KIR2DL1} CD158a,h {KIR2DL1 and KIR2DS1}, CD158b {KIR2DL2}, CD161, NKG2A, NKG2C, NKG2D, Nkp44, NKp46).Additionally,250 μg protein from cell extracts of CB and PB CD56Dim were used to perform quantitative differential protein profiling using tandem mass spectrometry (MS/MS)(Lim et al Lab Invest 2004) CD56+ selection yielded >89% purity (PB-96%, CB-89%). There was no statistical difference (mean + SEM) in NKR expression between the CB CD56dim and PB CD56dim. The PB vs. CB CD56bright had significant increased expression of KIR2DL2 (20.31 + 2.27 vs. 9.43 + 0.82, p< 0.012) only. The CB CD56dimvs. bright had increased CD16 expression (85.06 + 6.75 vs. 40.91 + 5.74, p< 0.004) only. Proteomic data showed that 33 and 37 proteins were over and under expressed by > 2 fold between CB and PB CD56dim NK cells. The functional categories of differentially expressed proteins were binding (46%), catalytic (17%), signaling (15%), transcription (15%), enzyme (3%), structural (2%), and transport (2%). CB compared to PB underexpressed Inositol 1,4,5-triphosphate receptor type 3, mitogen-activated protein kinase 5, and natural cytotoxicity triggering receptor 3 precursor by 8.33, 6.67, and 2.5 fold decrease, respectively. The CB compared to PB overexpressed neurogenic locus notch homolog protein 2 precursor, pleckstrin homology domain-containing family A member 1, and transcriptional repressor NF-X1 by 16.67, 7.14, and 5.26 fold increase, respectively. While PB vs. CB CD56dim and PB vs. CB CD56bright had similar NKR expression, CB vs. PB CD56dim NK cells had protein expression differences in 70 proteins, mostly in catalytic and binding proteins, which may influence their cytotoxic capacity. We hypothesize that CB CD56dim, in part contribute to the GVL effect post HLA disparate UCBT, and that differentially expressed proteins in CB vs. PB CD56dim may contribute to disparate cytotoxic activity.

98th AACR Annual Meeting-- Apr 14-18, 2007; Los Angeles, CA