Richard J. Mahoney

The flow cytometric crossmatch and early renal transplant loss.

Data from this retrospective study indicate that a positive two-color T and/or B cell flow cytometric crossmatch (FCXM) is predictive of early renal allograft loss (less than 2 months) in cadaveric kidney donor recipients who had a negative crossmatch by the antihuman globulin complement-dependent cytotoxicity technique. Among 90 cadaveric kidney donor recipients (67 primary, 23 regrafts), 14 (8 primary, 6 regrafts) lost their renal allografts within 2 months, and 10 of the 14 were FCXM positive and HLA sensitized. The remaining 76 allografts survived beyond 2 months, 12 of which were FCXM-positive. Thus, the FCXM sensitivity rate for detecting early graft loss was 71%, and the specificity rate was 84%. Cadaveric graft-loss rates at 2 months were 33% for primary and 60% for FCXM-positive regrafts in contrast to 7% for primary and 0% for FCXM-negative regrafts. The difference in early graft loss between FCXM-positive and FCXM-negative recipients was statistically significant (P less than 0.0001). Subset analyses of FCXM-positive graft recipients indicate: (1) previous early graft loss contraindicates transplantation of an FXCM-positive regraft (P = 0.03); and (2) panel reactive antibody (PRA) less than or equal to 10% at crossmatch is not associated with early graft loss (P = 0.04). There was no significant difference in 1-year graft survival between primary and regrafts in either FCXM-negative recipients (85% vs. 77%, respectively) or FCXM-positive recipients (67% vs. 40%). All 12 of the FCXM-positive primary and regrafts that survived 2 months continued to function at 2 years. Stepwise logistic regression analysis of 5 independent predictor variables (FCXM status, gender, primary vs. regraft status, PRA level, and HLA mismatched antigens) indicated that the FCXM test was the best predictor of early graft loss. When FCXM results of the 90 cadaveric graft recipients were ranked in three groups, an FCXM channel shift of 29 or greater (third tertile) on a 1024 channel log scale was associated with a 7.0-fold (95% confidence interval 1.9-25.5) increased risk of early graft failure when compared to the first two tertiles. These data indicate that the FCXM offers an additional approach for identifying sensitized patients at risk of early renal allograft loss.

Alloantigens of the Human T (HT) genetic region of the HLA linkage group

This article describes an approach that characterizes alloantisera reactive with new determinants on mitogen-activated human lymphocytes. These markers, which are tentatively called HT-antigens, are different from the classical HLA-A,C,C, and DR antigens but are associated with beta 2-microglobulin. Several alloantisera were tested extensively on lymphocytes that were treated initially with an antigen-blocking technique using turkey anti-beta 2-microglobulin and turkey anti-p29,34 sera or with an antigen-modulation technique using xeno- and alloantisera. It was concluded that these tested antisera recognized three different determinants (HT1, HT3, and HT (1 + 3) that appeared to segregate with the HLA-A locus of the HLA haplotype. HT antigens may be analogous to the murine TL-Qa antigens since HT antigens are associated with beta 2-microglobulin, are generally related to the HLA region, and are expressed on mitogen activated T cells but not on resting T cells.

Serological identification of thymocyte differentiation antigens.

We have examined subfractions of human thymocytes for the expression of novel differentiation antigens. Non-HLA alloantisera procured from multiparous women served as antibody probes. Thymocytes from five individuals were sequentially separated by discontinuous Percoll density gradient centrifugation and a peanut agglutinin (PNA) panning technique. Subfractions were selected and examined for their relative intensity of HLA class I and CD1 antigens as determined by cytofluorometric analysis. Two subfractions were characterized as follows: an immature population (Fr6 PNA-) expressed a high level of CD1 (OKT6 binding) antigen and a low level of class I HLA antigen; and a more mature fraction (Fr3 PNA-) expressed minimal amounts of CD1 antigen and relatively high levels of HLA class I molecules. Fr6 PNA+ and Fr3 PNA- thymocytes were tested for their reactivity with a panel of non-HLA alloantibodies as determined by cytofluorometric analysis. We observed that three alloantibodies demonstrated strong fluorescence staining with Fr6 PNA+ thymocytes only, whereas three other alloantibodies reacted with both the Fr6 PNA+ and the Fr3 PNA- subfractions. All six alloantibodies failed to react with peripheral T cells. However, the six antibodies did react with a panel of cultured T lymphoblastoid leukemic cells and fresh leukemic T cells. Blocking studies demonstrated that these alloantibodies do not bind beta 2-microglobulin-associated determinants. These results suggest that the alloantibodies detect thymocyte differentiation antigens (TDA) that are shared by or are cross-reactive with antigens expressed on certain leukemia T cells. The non-beta 2m-associated TDA antigens are not expressed on normal resting T cells.

HLA-DMA allele polymorphism: no impact on kidney allograft outcome

The purpose of this study was to analyze the association of HLA-DMA alleles with rejection episodes and early graft loss (EGL) in renal transplant recipients. One hundred and eighty four HLA-DMA alleles were retrospectively analyzed by DNA sequence analysis in 92 kidney transplant recipients. The gene frequencies of HLA-DMA *0101, *0102, *0103 and *0104 were found to be similar in all recipients, regardless of rejection vs non rejection episodes and EGL incidence. In conclusion, HLA-DMA allele polymorphism did not impact renal allograft outcome.

Increased fluidity of serum lipids and development of spontaneous mammary tumors in C3H mice

SummaryThe degree of lipid fluidity (LFU) was quantitatively monitored by fluorescence polarization analysis of the hydrocarbon fluorescent probe diphenylhexatriene when embedded in artificial and biological lipid complexes. The results have shown a marked increase in LFU in serum lipids associated with the development of spontaneous mammary tumors in C3H mice. An increase in serum LFU was observed during the initiation of primary tumors. The serum LFU further increases as a function of increase in the tumor volume. This increase was not observed when animals were given transplants of syngeneic, spontaneously arising mammary tumors or following implants of antigenically inert glass beads. Since the serum LFU in C57BL/6, NZB and A/JAX non-tumor-bearing mice was found to be significantly lower than in C3H non-tumor-bearing mice, it is suggested that alterations in the dynamics of serum lipids in the C3H system may have a direct relation to the induction and/or growth of spontaneous tumors in these mice. Moreover, experiments carried out with an artificial membrane model system have shown that the dynamics of a lipid complex are directly determined by its lipid composition. The three major parameters that determine the LFU of a lipid domain are: (a) the relative amounts of different phospholipids; (b) the molar ratio of cholesterol to phospholipids; and (c) the degree of saturation of the fatty acids. It is therefore suggested that alterations of this kind may occur in serum lipids during spontaneous mammary tumor development in C3H mice.