, 10-42). Using the Andersen-Gill proportional hazards regression model for the analysis of relapse-free survival, we found that PCR-positive findings in samples from BM and/or PB at any given time-point after transplantation were associated with an increased estimated hazard ratio of 4.5 in comparison with a PCR-negative finding (P = 0.013). On the other hand, patients included while they were in first remission had a smaller estimated hazard ratio of 0.3 when compared with patients with a history of previous treatment failure (P = 0.048). For the latter group of patients, this translates into a significantly smaller probability of relapse-free survival in comparison to patients who were in first remission at the time of PBSC-mobilization (P = 0.012). In conclusion, the remission status of the patients before autografting and the PCR status as assessed on the occasion of follow-up examinations are significant prognostic parameters for relapse-free survival in patients with follicular lymphoma undergoing high-dose therapy with PBSC autografting.

To elucidate factors contributing to the effectiveness of allogeneic hematopoietic stem cell transplantation (alloHCT) in high-risk CLL, immune interventions, GvHD and clinical outcome of 77 consecutive patients allografted for CLL were analyzed. Immune modulation (immunosuppression tapering, rituximab-augmented donor lymphocyte infusions) was guided by minimal residual disease (MRD) monitoring and commenced at a median of 91 (22-273) days after alloHCT, resulting in a probability of being event free and MRD-negative 1 year after transplant of 57% (84% in those encountering chronic GvHD). Patients who were event free and MRD-negative at the 12-month landmark had a 4-year PFS of 77% and largely remained durably MRD-negative if MRD clearance had occurred subsequent to immune modulation. Three-year overall survival, PFS, relapse incidence and non-relapse mortality of all 77 patients were 69, 57, 26 and 24%, respectively. Survival was not affected by EBMT risk category but by active disease at alloHCT, which could not be overcome by intensification of conditioning. Twenty-three patients who experienced relapse post alloHCT had a survival of 56% at 2 years after CLL recurrence. In conclusion, MRD-guided immune modulation after alloHCT for high-risk CLL can provide durable MRD clearance in more than half of the patients.

The expression of six antigenic epitopes on plasma Tg and tissue-derived Tg was investigated using mouse mabs in immunoradiometric assays. The sensitivity of the assays ranged between 0.5 and 1.5 micrograms l-1. Plasma thyroglobulin of 15 normal individuals and 18 patients with metastatic, differentiated thyroid cancer was analysed. Whereas five monoclonals produced values comparable to the conventional RIA system, the monoclonal antibody Tg 158 did not detect any Tg in the normal individuals and only low levels in two of the cancer patients with the highest Tg levels. In contrast, dilutions of extracts of three different euthyroid goitre samples and three different samples of differentiated thyroid cancer revealed no difference in the antigenic expression of all six epitopes, including the Tg 158 epitope. Papain digestion of purified Tg resulted in a 76 kD fragment which showed immunoreactivity for Tg 158 as well as for Tg 11. No interference of the binding of Tg 158 by T3, T4 or DIT could be detected. We conclude that the monoclonal antibody Tg 158 detects an epitope which is present in thyroid tissue-derived Tg but not in circulating thyroglobulin. This antibody might be useful for the investigation of the secretory process of thyroglobulin from the thyrocytes into the circulation.

It was the aim of this study to examine the prognostic value of the detection of minimal residual disease (MRD), with the help of the polymerase chain reaction (PCR), in patients with non-Hodgkin's lymphoma (NHL) and multiple myeloma (MM) who underwent sequential high-dose therapy with peripheral blood progenitor cell (PBPC) support, and in patients with acute myeloid leukemia (AML) of the subclass M4Eo who underwent high-dose consolidation therapy. Basis for the application of a PCR assay in these disease entities are the following specific gene rearrangements: the t(14;18) translocation in a high percentage of NHL, the clonal rearrangement of the Ig heavy chain locus resulting in a unique complementary determining region 3 (CDR3) for MM region and the inversion 16 characteristic for the M4Eo subclass of AML. Before the G-CSF-supported cytotoxic chemotherapy was given, 65% of the 52 patients with low- and intermediate-grade NHL enrolled into the study had PCR+ bone marrow (BM) and/or peripheral blood (PB) samples. The majority of patients (29 of 52) were autografted with a PCR+ transplant. The proportion of harvests containing t(14;18)+ cells was two-fold less in patients mobilized in first remission than in those with a history of previous treatment failure. This was also reflected when examining the B cell contents of the harvests measured as CD19+ cells with a 3.3-fold smaller proportion of CD19+ cells in leukapheresis (LP) products of patients mobilized in first remission. Patients who received a PCR- transplant are in remission and remained PCR- in BM and PB samples post-transplantation. Conversion to PCR-negativity in BM and PB samples post-transplantation was observed in 11 of 19 patients who were also in remission. In contrast, 6 of 29 patients who were autografted with PCR+ products relapsed, while 4 of them presented with PCR- samples on several occasions post-transplantation. In patients with MM, the assessment of MRD in PBPC harvests was based on the CDR3 regions of the Ig heavy chain locus as a marker for clonality. The great majority of LP products (17 out of 19) contained tumor cells. To prove positive enrichment procedures for the elimination of tumor cells, CD34+ and CD19+ cell fractions obtained from LP samples in an experimental setting via preparative flow cytometry were analyzed for MRD resulting in PCR-negativity for all CD34+ fractions. The results of the four patients with AML M4Eo and inversion 16 are preliminary, with a tendency of persistence of PCR-positivity after finishing the high-dose consolidation therapy. In one case, recurrence of disease was accompanied by an increase of the signal strength in the PCR assay. Longer follow-up periods are necessary to determine the prognostic value of these PCR findings in the different disease entities.

The T-cell-accessory-cell interaction in mixed lymphocyte cultures was investigated in 25 patients following autologous bone marrow transplantation (ABMT) using autologous bone marrow treated in vitro with the cyclophosphamide derivative ASTA Z 7557. In a previous study using the same group of patients, T cells failed to synthesize interleukin-2 (IL-2) and proliferate in response to CD3- and CD2- mediated stimuli even in the presence of exogenous IL-2. To investigate whether this defect in IL-2 synthesis and proliferation was caused by defective cell-to-cell interactions, we analyzed mixed lymphocyte reactions (MLR) using T cells and irradiated non-T cells. When normal T cells from 10 different healthy subjects were challenged with allogeneic normal non-T cells, IL-2 production and proliferation were observed. In contrast, when normal T cells were cultured with non-T cells derived from patients found between 20 and 330 days after ABMT, no IL-2 secretion and no proliferative responses could be seen. The addition of lymphokines such as interleukin-1 (IL-1), interleukin-3 (IL- 3), tumor necrosis factor (TNF), granulocyte-macrophage colony stimulating factor (GM-CSF), and interferon-gamma (IFN-y) did not improve the reactions. Furthermore, when patients' T cells were incubated with normal, irradiated non-T cells, defective IL-2 synthesis or proliferative response was obtained. However, when IL-2 was added to these cultures, an improvement in proliferative reactions was observed. Taken together, these new data provide additional evidence that T cells early in ontogeny possessed an intrinsic defect in IL-2 synthesis and that physical cell-to-cell contact between patients' T cells and allogeneic accessory cells induced functional responsiveness to exogeneous IL-2.