Pre-transplant donor HLA-specific antibodies: characteristics causing detrimental effects on survival after lung transplantation.

BACKGROUND: The impact of Luminex-detected HLA antibodies on outcomes after lung transplantation is unclear. Herein we have undertaken a retrospective study of pre-transplant sera from 425 lung transplants performed between 1991 and 2003. METHODS: Pre-transplant sera, originally screened by complement-dependent cytotoxicity (CDC) assays, were retrospectively tested for the presence of HLA-specific antibodies using HLA-coated Luminex beads and C4d deposition on Luminex beads. The results were correlated with graft survival at 1 year. RESULTS: Twenty-seven patients were retrospectively identified as having been transplanted against donor-specific HLA antibodies (DSA) and 36 patients against non-donor-specific HLA antibodies (NDSA). DSA-positive patients had 1-year survival of 51.9% compared with 77.8% for NDSA and 71.8% for antibody-negative patients (p = 0.029). One-year survival of patients with complement-fixing DSA was 12.5% compared with 62.5% for non-complement-fixing DSA, 75.8% for non-complement-fixing NDSA and 71.8% for antibody-negative patients (p < 0.0001). DSA-positive patients with mean fluorescence intensity (MFI) >5,000 had 1-year survival of 33.3% compared with 71.4% for MFI 2,000 to 5000 and 62.5% for MFI <2,000 (p = 0.0046). Multivariable analysis revealed DSA to be an independent predictor of poor patient survival within 1 year (p = 0.0010, hazard ratio [HR] = 3.569) as well as complement-fixing DSA (p < 0.0001, HR = 11.083) and DSA with MFI >5,000 (p = 0.0001, HR = 5.512). CONCLUSIONS: Pre-formed DSA, particularly complement-fixing DSA, and high MFI are associated with poor survival within the first year after lung transplantation. Risk stratification according to complement fixation or MFI levels may allow for increased transplantation in sensitized patients.

Inverse gas chromatography: investigating whether the technique preferentially probes high energy sites for mixtures of crystalline and amorphous lactose.

PURPOSE: Inverse gas chromatography (IGC) is rapidly gaining popularity as a method for assessing powder surface energy. It is vital to understand what IGC measures if results are to be useful. This work examines the view that IGC preferentially measures high-energy sites on a powder surface. METHODS: Mixtures of amorphous (high-energy) and crystalline (lower energy) lactose particles were prepared and tested using IGC with nonpolar probes. The surface area of the particles was measured in situ in the inverse gas chromatograph. RESULTS: The results were weighted averages of the surface energy for amorphous and crystalline material until the amorphous content exceeded 15% w/w of the sample, after which the surface energy become equivalent to that of the amorphous form. The amorphous content dominated when the surface area was 40% of the total area. Given that the amorphous particles were much smaller and adhered to the crystalline ones, it is reasonable to conclude that many (most) of the binding sites on the surface of the crystalline particles were masked by the amorphous particles by the time that the amorphous content dominated the surface energy measurements. CONCLUSIONS: IGC does not simply measure the high-energy sites in the packed column, but equally there is a complex process that results in measured data on mixtures not being a weighted mean of the surface energy of the two components.