Annemarie Hekman

Association of lactoferrin with other proteins, as demonstrated by changes in electrophoretic mobility.

Lactoferrin in a number of human body fluids was found to possess different electrophoretic mobilities, while being immunologically identical. The isolated protein migrated slower than any of the naturally occurring forms. This phenomenon was found to be due to the property of human lactoferrin to interact strongly with acidic macromolecules, forming complexes with a faster migration than the single protein. Beside electrostatic interactions also other forces seem to be involved in the complex formation.

Initial experience with treatment of human B cell lymphoma with anti-CD19 monoclonal antibody

SummarySix patients with progressive B cell non-Hodgkins lymphoma have been treated with an IgG2a mouse monoclonal antibody (mAb) against the B cell differentiation antigen CD19, with total doses varying from 225 mg to 1000 mg. Free mAb was detected in the serum after doses of 15–30 mg. After the mAb infusions the number of circulating tumour cells was temporarily reduced, but in some cases antibody-coated cells remained in the circulation for several days. mAb penetrated to extravascular tumour sites; in general higher doses were required to saturate cells in the lymph nodes than to sensitize tumour cells in the bone marrow. mAb doses of up to 250 mg were given i.v. over 4 h without major toxicity. One patient twice achieved a partial remission after two periods of mAb treatment with an 8-month interval; the second remission lasted for 9 months. One patient showed a minor response. None of the patients made antibodies against the mouse immunoglobulin. Serum immunoglobulin levels were followed as a measure of the function of the normal B cell compartment; no significant changes were seen up to 6 months after mAb treatment.

Treatment of low-grade non-Hodgkin's lymphoma with continuous infusion of low-dose recombinant interleukin-2 in combination with the B-cell-specific monoclonal antibody CLB-CD19

Seven patients with low-grade non-Hodgkins lymphoma were treated with a combination of a murine monoclonal antibody directed against the B-cell-specific antigen CD19 (CLB-CD10), given twice weekly, and continuous infusion of low-dose recombinant interleukin-2 (rIL-2). We demonstrated stable serum CLB-CD19 levels throughout the 12 weeks of treatment, and homing of the antibody into the tumour sites. A variable degree of antigenic modulation was noted. Prolonged treatment resulted in a sustained increase in the number of natural killer cells in the circulation with enhanced cytotoxic capacity, including antibody-dependent cellular cytotoxicity. During the first weeks of treatment, T cell activation occurred in the majority of patients. Toxicity was related to the rIL-2 treatment and consisted of transient constitutional symptoms and a flu-like syndrome without organ dysfunction. A partial remission occurred in one patient, and in another patient who was primarily leukaemic a greater than 50% reduction of circulating B cells was noted. An antitumour effect occurred early during treatment and could not be related to rIL-2-induced modulation of natural killer cell or T lymphocyte activation.

A phase I study of prolonged continuous infusion of low dose recombinant interleukin-2 in melanoma and renal cell cancer. Part II: Immunological aspects.

The optimal schedule for recombinant interleukin-2 (rIL-2) administration is unclear. Because the clinical and immunological effects of prolonged continuous exposure to rIL-2 are unknown, we have conducted a phase I study to assess the toxicity and feasibility of continuous low dose infusion of rIL-2 (EuroCetus) using central venous access with a portable infusion device on an out-patient basis. Twenty-two patients entered the study, 13 with melanoma and nine with renal cell cancer, age range 26-66 years (median 51), performance status less than or equal to 1. They were treated with one of the following doses per m2 per 24 h: 0.18 x 10(6) IU, 0.6 x 10(6) IU, 1.8 x 10(6) IU, 3 x 10(6) IU, 6 x 10(6) IU and 9 x 10(6) IU. Toxicity was evaluable in 20 patients receiving greater than or equal to 3 weeks treatment duration or in whom treatment was discontinued prematurely because of toxicity. Constitutional symptoms consisting of fatigue, malaise and fever up to 40 degrees C without significant organ dysfunction occurred with doses greater than or equal to 1.8 x 10(6) IU m-2. The maximum tolerated dose was 6 x 10(6) IU m-2 24 h-1. In all patients toxicity reached a peak at 3 weeks and resolved thereafter despite continued rIL-2 treatment. Peripheral blood eosinophilia (up to 66% of white blood cell count) followed the same pattern. An infection of the central venous access occurred in 55% of the patients but this was mostly asymptomatic. Thirteen patients were treated greater than or equal to 6 weeks and were evaluable for tumour response. A partial remission occurred in a patient with melanoma with a dose of 1.8 x 10(6) IU rIL-2 m-2 24 h-1.

Antigenic determinants on lysine-rich histones.

Abstract 1. 1. Rabbit sera were prepared containing antibodies which reacted specifically with lysine-rich histones. Immunofluorescent studies showed specific staining of cell nuclei with these antisera after appropriate absorption of the sera with non-histone proteins. 2. 2. Complement fixation studies revealed that lysine-rich histones from rat tissues contain antigenic determinants common with other species and also rat-specific antigenic determinants. When the amino-terminal region (amino acid residues 1–73) was detached from the lysine-rich rat liver histone, the remaining fragment still contained both types of antigenic determinants. 3. 3. The antisera could not distinguish between lysine-rich histones from normal rat tissues and those from rat tumors.

Enhancement of the antibody-dependent cellular cytotoxicity of human peripheral blood lymphocytes with interleukin-2 and interferon alpha.

Antibody-dependent cellular cytotoxicity (ADCC) is regarded as an important mechanism by which monoclonal antibodies (mAb) can exert an antitumour effect in vivo. It may be possible, therefore, to enhance the therapeutic efficacy of mAb by cytokines that are able to enhance the ADCC of human CD3−, CD56+, CD16+ natural killer (NK) cells. We investigated in vitro the effects of recombinant interferon α (rIFNα) and recombinant interleukin 2 (rIL-2), alone or in combination, on the ADCC of human peripheral blood NK cells. Both cytokines enhanced the ADCC of the human effector cells. rIFNα induced a maximally increased ADCC after an exposure of human effector cells to 20 IU/ml for 15–30 min, while rIL-2 induced optimal ADCC after incubation of the cells for 2 days in 20–50 U/ml. We now show that activation of the NK cells with a combination of rIL-2and rIFNα induced significantly higher levels of ADCC than either cytokine alone. The highest ADCC was induced if the cells were first exposed to rIL-2 before rIFNα was added to the culture. Culture of NK cells in medium or rIL-2 decreased the expression of FcγRIII (CD16), indicating that intensity of CD16 expression and level of ADCC are not directly correlated, although blocking experiments with a mAb directed against CD16 showed that this FcγR was essential for ADCC of the human effector cells.

Reconstitution of recombinant interleukin-2 (rIL-2) : a comparative study of various rIL-2 muteins

In a previous clinical study using a continuous infusion schedule of recombinant interleukin-2 (rIL-2) we noted a nearly complete loss of activity of EuroCetus rIL-2 when dissolved in 10 ml saline and infused at a very low rate through a plastic infusion device. In the present study, we demonstrated that the loss resulted from a concentration-dependent precipitation of rIL-2 in saline and adherence of the protein to the tubing material. These phenomena were not noted for four other rIL-2 muteins tested [Glaxo, Hoffmann-LaRoche, Amgen (2 muteins)]. EuroCetus rIL-2 was found to be completely soluble in water and 5% glucose.

HGF/SF and its receptor c-MET play a minor role in the dissemination of human B-lymphoma cells in SCID mice

SummaryThe MET protooncogene, c-MET, encodes a cell surface tyrosine kinase receptor. The ligand for c-MET is hepatocyte growth factor (HGF), also known as scatter factor (SF), which is known to affect proliferation and motility of primarily epithelial cells. Recently, HGF/SF was also shown to affect haemopoiesis. Studies with epithelial and transfected NIH3T3 cells indicated that the HGF/SF–c-MET interaction promotes invasion in vitro and in vivo. We previously demonstrated that HGF/SF induces adhesion of c-MET-positive B-lymphoma cells to extracellular matrix molecules, and promoted migration and invasion in in vitro assays. Here, the effect of HGF/SF on tumorigenicity of c-MET-positive and c-MET-negative human B-lymphoma cell lines was studied in C.B-17 scid/scid (severe combined immune deficient) mice. Intravenously (i.v.) injected c-MET-positive (BJAB) as well as c-MET-negative (Daudi and Ramos cells) B-lymphoma cells formed tumours in SCID mice. The B-lymphoma cells invaded different organs, such as liver, kidney, lymph nodes, lung, gonads and the central nervous system. We assessed the effect of human HGF/SF on the dissemination of the B-lymphoma cells and found that administration of 5 μg HGF/SF to mice, injected (i.v.) with c-MET-positive lymphoma cells, significantly (P = 0.018) increased the number of metastases in lung, liver and lymph nodes. In addition, HGF/SF did not significantly influence dissemination of c-MET-negative lymphoma cells (P = 0.350 with Daudi cells and P = 0.353 with Ramos cells). Thus the effect of administration of HGF/SF on invasion of lymphoma cells is not an indirect one, e.g. via an effect on endothelial cells. Finally, we investigated the effect of HGF/SF on dissemination of c-MET-transduced Ramos cells. In response to HGF/SF, c-MET-transduced Ramos cells showed an increased migration through Matrigel in Boyden chambers compared to wild-type and control-transduced Ramos cells. The dissemination pattern of c-MET-transduced cells did not differ from control cells in in vivo experiments using SCID mice. Also no effect of HGF/SF administration could be documented, in contrast to the in vitro experiments. From our experiments can be concluded that the HGF/SF–c-MET interaction only plays a minor role in the dissemination of human B-lymphoma cells.

Possible role for cytotoxic lymphocytes in the pathogenesis of acute interstitial nephritis after recombinant interleukin-2 treatment for renal cell cancer

A patient with renal cell cancer developed acute renal failure due to biopsy-proven acute tubulo-interstitial nephritis (AIN) in the 6th week of continuous infusion of 9 × 106 IU m−2 day−1 recombinant interleukin-2 (rIL-2). We investigated whether the AIN was the result of a cellular cytotoxic reaction induced by the rIL-2 treatment. The cytolytic activity of cryopreserved peripheral blood lymphocytes (PBL), isolated before and at the end of the rIL-2 treatment (at the time of AIN), was studied after 5 days of culture with or without rIL-2 or anti-CD28 and immobilized anti-CD3 antibodies. The PBL isolated before and at the end of the rIL-2 treatment showed cytolytic activity towards a number of allogeneic targets. However, only the PBL isolated at the end of the rIL-2 treatment showed, when stimulated with rIL-2 in vitro, significant cytolytic activity against an autologous renal cell line cultured from the AIN biopsy specimen and against an allogeneic renal cell cancer cell line. These PBL displayed no enhanced killing capacity towards autologous PBL and the melanoma cell line M14. These observations suggest that the AIN may be the result of a cytotoxic lymphocyte-mediated reaction induced by the rIL-2 treatment.

Mouse monoclonal antibodies direct phagocytosis of tumor cells by human monocytes

Human peripheral blood monocytes were found to be capable of phagocytizing human B-non Hodgkins lymphoma (NHL) cells coated with mouse monoclonal antibodies (MoAbs). The MoAbs used recognized idiotypic determinants on the surface immunoglobulin (Ig) of the tumor cells. MoAbs of IgG1 and IgG2a subclass were equally effective in inducing phagocytosis. Preincubation of the monocytes with heat aggregated Ig from human or mouse serum inhibited phagocytosis to the same degree, suggesting involvement of an Fc receptor on the monocytes that binds both human and mouse antibodies.