Lymphocytotoxic cross-matching performed on spleen cells: immunomagnetic technique versus current KN (Kissmeyer-Nielsen) technique

Indications of immunological tolerance in kidney transplantation

As a complication to immunosuppressive treatment in allotransplantation, malignant diseases such as post-transplant lymphoproliferative disorder (PTLD) may occur. The patient in the present case is a 21-year-old man transplanted at the age of 11 with a kidney from his mother and at the age of 15 with a kidney from his father. During the immunosuppressive treatment the patient developed PTLD resulting in the withdrawal of the immunosuppressive drugs. At the time of writing, the immunosuppressive drugs have been withdrawn for more than 3 years. We report the findings of a state of donor-specific tolerance occurring after transplantation. Post-transplant cells from the patient show a non-reactive response in mixed lymphocyte cultures (MLCs) to cells from both the mother and the father. We demonstrate a reduction in the mRNA expression of the Thl cytokines IL-2 and IFN-gamma in the very same MLCs. The expression of Th1 cytokine mRNA was measured semi-quantitatively using competitive reverse transcription-polymerase chain reaction (RT-PCR). The reduction in the Th1 cytokine mRNA expression is not seen in the MLCs with patient cells against cells from a paternal HLA-A, B and DR-matched individual, suggesting the influence of other allorecognition factors than HLA-A, B and DR. Detection in vitro of a lowered expression of Th1 cytokine mRNA supports the notion of these mRNAs as indicators of post-transplant tolerance. Further studies will reveal whether the cytokine mRNA measurements on short time stimulated lymphocytes can be used more generally as a monitoring parameter of tolerance in kidney transplantation.

HLA typing and lymphocytotoxic crossmatches using conventional techniques or immunobeads. A comparative study

In a prospectively designed comparative study, HLA class I and class II typing was performed after B/T lymphocyte separation by nylon wool (NIH technique) or using immunomagnetic beads (IMB technique). Samples from 70 healthy individuals (group A) and from 47 patients with potential typing problems (group B) were examined. Complete typing failures occurred more frequently with NIH than with IMB. Except for class I in group A, the rate of correct decisions for antigen assignment was significantly higher with IMB. For class II serum reactions, specificity, predictive value and efficiency were superior for IMB, while sensitivity appeared higher for NIH. This can possibly be explained by a prozone effect which was observed in 9 of 36 titration experiments only with the IMB technique. Correlation of both methods in 104 crossmatches prior to kidney transplantation was poor using peripheral blood lymphocytes, but excellent with spleen cells. In addition to the important advantages of the IMB technique for potential problem cases, especially for class II, typing time is reduced to one third, which is of particular clinical importance in kidney transplantation. However, lymphocytotoxic crossmatches prior to transplantation, if performed by IMB, should be carried out using different serum dilutions or with donor spleen cells instead of peripheral blood lymphocytes.

Clinical applicability of the immunomagnetic beads technique for serological crossmatching in renal transplantation

The aim of the present prospective study was to investigate the clinical applicability of the immunomagnetic (IM) beads technique for serological crossmatching (XM) in renal transplantation. The IM XM were read after various periods of incubation, and the results were compared with those obtained by the conventional Kissmeyer-Nielsen (KN) technique. A total of 132 sera from 96 potential recipients were tested against cells from 62 donors. Eight-nine KN T-cell XM-negative renal allograft transplantations were performed, and the IM XM results were related to clinical 3-month follow-up data (incidence of primary non-function, never functioning grafts, graft losses and rejection episodes). The IM technique was clearly more sensitive than KN, and sensitivity increased markedly with increasing duration of incubation. KN-, IM+ reactions were predominantly found among sera from patients with panel-reactive antibodies (PRA, 2p less than 0.01), and thus probably caused by HLA antibodies. However, positive IM XM, appearing after more than 35 min of incubation, did not influence the overall clinical outcome in the observation period. With reading after exactly 35 min of incubation, XM results obtained by IM and KN techniques correlated well. Thus, we believe, that the IM XM technique will be as safe and effective in avoidance of hyperacute rejections as the conventional assay. In the present material, the incidence of primary nonfunction was significantly (2p = 0.0023) higher among PRA+ recipients compared to PRA- patients. To conclude, we recommended the IM technique with reading after exactly 35 min of incubation for easy, fast (70 min) and reliable XM, that is always possible to perform using peripheral blood.

Applications of automated simultaneous double fluorescence (SDF). II. HLA class I phenotyping using immunomagnetically separated T lymphocytes

HLA class I phenotyping was performed using T-lymphocyte populations isolated by immunomagnetic beads (IMBs) coated with monoclonal antibodies with specificity for CD2, CD4 or CD8. The results were compared to those obtained using density gradient-separated lymphocytes (PBL). The typing trays were read by the automated simultaneous double-fluorescence (SDF) technique previously established in our laboratory using an Astroscan 2100 system. The aims of the present study were to establish whether the advantages of IMB lymphocyte separation and automated plate reading by SDF were complementary and whether the results obtained by IMB-SDF and PBL-SDF were concordant. Similarity coefficients for paired results obtained by IMB-SDF and PBL-SDF varied between 0.825 using anti-CD8-coated IMBs and 0.914 using anti-CD4-coated IMBs with a consistent excess of stronger results observed with the PBL-SDF technique. The variations observed did not result in incorrect phenotype assignment but would significantly influence a cross-matching test. These results illustrate the feasibility of using IMB-separated lymphocytes for HLA phenotyping by SDF.