Regulated expression of gp130 and IL-6 receptor alpha chain in T cell maturation and activation

The functional receptor for the inflammatory cytokine IL-6 is composed of the ligand binding IL-6 receptor alpha chain (IL-6R alpha) and the signal transducing chain gp130, which is a shared component of multiple cytokine receptors. We analyzed the surface expression of gp130 and IL-6R alpha in thymocytes and peripheral T cells. While all thymocytes expressed gp130 throughout thymic maturation, they gained expression of IL-6R alpha at the CD4 or CD8 single-positive stage. Approximately 10-30% of the CD4-CD8+ and 40-50% of the CD4+CD8- thymocytes expressed IL-6R alpha. Within the CD4+CD8- population, the IL-6R alpha- subpopulation was cortisone sensitive, appeared immature according to the cell surface markers expressed and failed to proliferate after TCR cross-linking. Peripheral T cells were predominantly gp130+ and IL-6R alpha+, but down-regulated gp130 and IL-6R alpha expression upon TCR engagement in vitro and in vivo. Peripheral gp130low/-IL-6R alphalow/- T cells expressed surface markers characteristic of memory T cells. We show that gp130 and IL-6R alpha are expressed in a regulated manner in T cells, depending on the developmental and functional stage.     

Accumulation of a recombinant immunotoxin in a tumor in vivo: fewer than 1000 molecules per cell are sufficient for complete responses

Recombinant immunotoxins have been shown to cure human tumor xenografts in mice, but their biodistribution to both tumors and normal organs has not been reported. Anti-Tac(Fv)-PE38 is a single-chain recombinant immunotoxin composed of the variable heavy and light domains of the anti-Tac monoclonal antibody that reacts with the primate interleukin 2 (IL2) receptor alpha subunit (IL2R alpha or CD25) fused to a truncated form of Pseudomonas exotoxin (PE). 125I-labeled anti-Tac(Fv)-PE38 was given i.v. to immunodeficient mice each bearing two A431 tumors, one that expresses IL2R alpha (ATAC-4) and one that does not (A431, parental). A single i.v. dose of 4 microg/mouse caused complete regression of the IL2R alpha + tumor. At 6 h, over 6% of the injected dose/g was found in the ATAC-4 tumor, and 2% was in the A431 tumor. Uptake in the ATAC-4 tumor was higher than in any other tissue. Sections of tumor examined by autoradiography indicated that anti-Tac(Fv)-PE38 was distributed throughout the entire tumor, with some portions having higher uptake than others. By subtracting uptake in tumors without receptor (A431) from uptake in receptor-containing tumors (ATAC-4), we calculated that at least 400 molecules/cell specifically bound to IL2R alpha-positive tumor cells at 90 min and 750 molecules/cell bound at 360 min. This is similar to the 400-870 molecules/cell required for >99.9% killing of ATAC-4 cells growing as a monolayer. The results show that solid tumors in mice can be eradicated like cells in tissue culture, and that delivery of less than 1000 molecules/cell is sufficient to cause complete tumor regressions.     

Targeting Pseudomonas exotoxin to hematologic malignancies

Malignant cells of hematopoietic origin often express a variety of different growth factor receptors and antigens on their surface, at levels much higher than normal cells. These malignant cells can be selectively targeted with Pseudomonas exotoxin (PE) derivatives directed by interleukins 2, 4 and 6, and by Fv fragments of monoclonal antibodies to interleukin 2 receptor (IL2R) subunits, CD22 and other antigens present on these cells. Anti-Tac(Fv)-PE38, a single-chain recombinant immunotoxin which targets cells bearing the IL2Ra, is furthest along in preclinical development and is being prepared for clinical testing in patients with IL2Ra-positive leukemia, lymphoma and Hodgkin's disease.     

Human glioma cells overexpress receptors for interleukin 13 and are extremely sensitive to a novel chimeric protein composed of interleukin 13 and pseudomonas exotoxin

Recently, we have demonstrated that a spectrum of human adenocarcinoma cell lines express binding sites for interleukin 13 (IL-13). These cells are killed by a chimeric protein composed of human (h) IL-13 and a derivative of Pseudomonas exotoxin, PE38QQR (Debinski et al., J. Biol. Chem., 270: 16775-16780, 1995). The cell killing was hIL-13- and hIL-4-specific, indicating that a common binding site for the two cytokines is present in several solid tumor cell lines. Herein, we report that an array of established glioma cell lines is killed by very low concentrations of hIL-13-PE38QQR, often reaching <1 ng/ml (<20 pM). Glioma cells express up to 30,000 molecules of IL-13 receptor/cell which has intermediate affinity toward hIL-13. hIL-13-PE38QQR is more active (up to 3 logs difference in cytotoxic activities) than are the corresponding chimeric toxins containing hIL-4 or hIL-6. The cytotoxic action of hIL-13-PE38QQR is blocked by an excess of hIL-13 on all cell lines studied, and it is not neutralized by hIL-4 on some of these cells. Our results show that human brain cancers richly express receptors for IL-13. Furthermore, the interaction detected previously between receptors for IL-13 and IL-4 on solid tumors cell lines is of a qualitatively different character in U-251 MG and U-373 MG glioma cells. The receptor for IL-13 may represent a new marker of brain cancers and an attractive target for anticancer therapies.     

Serum levels of p55 and p75 soluble TNF receptors in adult acute leukaemia at diagnosis: correlation with clinical and biological features and outcome

The tumour necrosis factor (TNF)/TNF-receptor (TNFR) complex plays a role in the growth of leukaemic cells. We retrospectively investigated the relationship between pretreatment serum concentration of soluble TNFR (p55- and p75-sTNFRs) and outcome in adult acute myeloid (AML 82 cases) and lymphoid (ALL 44 cases) leukaemia. Both sTNFRs were significantly higher in AML (p55-sTNFR 4.53 +/- 3.7, median 3.75; p75-sTNFR 6.51 +/- 5.25 ng/ml, median 4.72) and ALL sera (3.31 +/- 1.5, median 2.95; 5.30 +/- 2.3 ng/ml, median 4.56, respectively) than in controls (1.89 +/- 0.5, median 1.98; 2.22 +/- 0.8 ng/ml, median 2.37) (P < 0.01 for both sTNFRs). Fresh leukaemic cells expressed p55- and p75-sTNFRs, which were modulated and released into the supernatant (SN) following short-term in vitro culture, suggesting that in vivo sTNFRs were also leukaemia-derived. Whereas no correlation was observed between sTNFRs and outcome in ALL, in AML higher p55-sTNFR levels (> 3.75 ng/ml) were associated with shorter disease-free survival (DFS) (P = 0.006) and overall survival (OS) (P = 0.0004). At multivariate analysis p55-sTNFR was the most significant predictor of DFS (P = 0.006) and OS (P < 0.001). Our data suggest that the prognostic significance of p55-sTNFR in AML could be related to relevant biological features of AML blasts.     

Co-stimulation of cultured peripheral blood mononuclear cells from intrinsic asthmatics with exogenous recombinant IL-6 produce high levels of IL-4-dependent IgE

Asthma is an inflammatory airway disorder, traditionally subdivided into extrinsic, immunoglobulin E (IgE)-mediated, and intrinsic asthma of unknown aetiology. IgE synthesis requires contact between T- and B-cells and a signal provided by interleukin (IL)-4, which can be modulated by IL-6. The objective of this study was to evaluate the effects of IL-4 and IL-6 on total IgE synthesis by peripheral blood mononuclear cells from intrinsic and extrinsic asthmatics. Peripheral blood mononuclear cells from intrinsic and extrinsic asthmatic patients and from healthy subjects were cultured and stimulated with pokeweed mitogen, recombinant IL-4 and IL-6. The IgE level in serum and supernatants was measured by an enzyme-linked immunoassay. Serum IgE was significantly lower in intrinsic asthma than in extrinsic asthma, but significantly higher than in control subjects. IgE production by cultured mononuclear cells from extrinsic asthmatics was not modified after exogenous IL-4 and IL-6 addition. However, intrinsic asthmatics showed enhancement of IgE synthesis in response to IL-4 stimulation, reaching a threefold increase of the spontaneous IgE values, when simultaneous recombinant IL-4 plus IL-6 stimulus was used. Our results indicate that exogenous recombinant interleukin-6 can significantly upregulate the interleukin-4-dependent immunoglobulin E synthesis in intrinsic asthma. This suggests that immunoglobulin E could also play a role in the pathogenesis of intrinsic asthma, in which an interleukin-6 threshold would be critical.     

Interleukin-6 (IL-6) inhibits thyroid function in the presence of soluble IL-6 receptor in cultured human thyroid follicles

Interleukin-6 (IL-6), a pleiotropic cytokine, is postulated to be involved in the pathogenesis of sick euthyroid syndrome, although the direct in vitro effects of IL-6 on human thyroid function are controversial. Because IL-6 signal can be transduced when the complex of IL-6 and soluble IL-6 receptor (sIL-6R) binds to gp 130, an IL-6 signal transducer, we studied the effects of IL-6 and sIL-6R on thyroid function, using human thyroid follicles obtained from patients with Graves' disease. IL-6 alone had no inhibitory effect on TSH-induced thyroid function (125I incorporation and organic 125I release), even at supraphysiological concentrations. However, in the presence of physiological concentrations of sIL-6R (100 ng/ml), IL-6 inhibited thyroid function dose dependently and completely, accompanied with the decreased ratio of 125I-T3/125I-T4 not only in the thyroid follicles but also in the culture medium. Thyroid follicles did not secrete sIL-6R but produced IL-6 constitutively. Consistent with these findings, sIL-6R inhibited thyroid function slightly at high concentrations. Furthermore, RT-PCR analyses revealed that human thyroid follicles expressed the messenger RNAs for IL-6 and gp130 but scarcely messenger RNA for IL-6R. These in vitro findings suggest that IL-6 alone hardly affects thyroid function in thyroid follicles in which IL-6R gene is scarcely expressed. However, because sIL-6R is present abundantly in serum, IL-6 in vivo would be capable of inhibiting the synthesis and release of T4 and, to a greater extent, T3 from the thyroid gland. These in vitro findings are at least partly related to the development of sick euthyroid syndrome.     

A compilation of mutations located in the cytochrome b subunit of the bacterial and mitochondrial bc1 complex

We used a SCID mouse xenograft model to study the in vivo growth patterns of primary leukemic cells from six patients with newly diagnosed B-cell precursor (BCP) acute lymphoblastic leukemia (ALL), including two patients with t(1;19) ALL, two patients with t(4;11) ALL, and two patients with t(9;22) ALL. Leukemic cells from these six patients caused overt leukemia in SCID mice with extensive multiple organ involvement. Leukemic BCP from SCID mice xenografted with leukemic cells from two t(9;22) ALL patients expressed very high levels of both VLA-4 and VLA-5 regardless of the tissue of origin. By comparison, in SCID mice xenografted with leukemic cells from the two patients with t(1;19) ALL and two patients with t(4;11) ALL, leukemic BCP from the bone marrow samples expressed high levels of VLA-4 as well as VLA-5, whereas the vast majority of leukemic BCP in the liver or spleen samples expressed neither of these adhesion molecules at significant levels. These results suggest that the expression of VLA-4 and VLA-5 on t(1;19) or t(4;11) leukemia cells likely determines their binding capacity to bone marrow stroma and may affect their migration to extramedullary tissues. Our findings are in accord with and extend previous studies which demonstrated that extracellular matrix and integrins influence development, compartmentalization, and migration of BCP during B-cell ontogeny. The described SCID mouse model system provides a unique opportunity to study the adhesion receptors which regulate the selective homing of human leukemic BCP to specific SCID mouse organs.     

Lymphocyte activation and cytokine production in autoimmune hemolytic anaemia (AIHA)

We studied 16 patients affected by autoimmune hemolytic anaemia (AIHA), both idiopathic and associated with other diseases (B and T lymphoma, B hepatitis, gastric carcinoma, systemic lupus erythematosus) or alpha-methyldopa therapy, in order to value T- and B-cell activation. We determined the count of T- and B-cell subsets in peripheral blood, the proliferative response of peripheral blood lymphocytes (PBL) to phytohemagglutinin (PHA) and to pokeweed mitogen (PWM), the percentage of CD25+ cells in culture and interleukin (IL)-1alpha, IL-2, IL-4, tumor necrosis factor (TNF)alpha and soluble IL-2 receptor (sIL-2R) levels in sera and in culture. Except for an increase in CD4+ and CD8+ T cell number in a case of AIHA associated with a T lymphoma and an increase in the percentage of CD5+ and PCA1+ B cells in two cases of AIHA associated with B lymphoma and with SLE, no further data showed a relationship with the disease possibly associated with AIHA, so both idiopathic and secondary AIHA cases were analyzed together. CD4+ T cells were reduced in number in 9 cases, while CD8+ T cells were reduced in 6 cases. The percentage of CD5+ B cells was increased in 5 cases. The percentage of PCA1+ cells was increased in all cases (mean +/- sd: 18 +/- 22 vs 0,2 +/- 1 in controls). The average PBL proliferative response to PHA was reduced (S.I. 71 +/- 55 vs 138 +/- 45 in controls) as well as that to PWM (S.I. 27 +/- 21 vs 75 +/- 24 in controls), despite IL-2 high levels, in all cases, in both sera (mean +/- sd: 648 +/- 351 pg/ml vs 16 +/- 4 pg/ml in controls) and culture supernatants (mean +/- sd: 1045 +/- 677 pg/ml vs 195 +/- 51 pg/ml in controls). In PHA stimulated cultures the percentage of CD25+ cells was reduced (mean +/- sd: 37 +/- 18 vs 63 +/- 14 in controls), sIL-2R levels were like controls in 7 cases. In sera sIL-2R levels were increased in all cases (mean +/- sd: 1256 +/- 465 U/ml vs 256 +/- 114 U/ml in controls), IL-1alpha was increased in all cases too, while IL-4 levels were increased only in 7 cases. Linear regression analysis generally showed a low relationship between S.I. and IL-2, IL-4 and sIL-2R levels in supernatants of PHA stimulated culture as well as between S.I. and the percentage of CD25+ cells. Taken together these data suggest a state of B- and T-cell hyperactivation in AIHA. The low PBL proliferative response in vitro, explained in previous studies as a temporary functional exhaustion, might be itself a sign of the complete lymphocyte activation occurring in vivo in AIHA.     

Suppressive effect of hepatitis B virus on the induction of interleukin-1 beta and interleukin-6 gene expression in the THP-1 human monocytic cell line

The major target organ for Hepatitis B Virus (HBV) is the liver, but extrahepatic sites including monocytes express receptors for HBV and may become infected. Therefore, we investigated the effect of HBV on the in vitro expression of interleukin-beta (IL-1 beta) and interleukin-6 (IL-6) by the monocytoid cell line THP-1, exposed to various stimuli (LPS, PMA or both). Nonstimulated THP-1 cells did not synthesize IL-1 beta and IL-6, even after in vitro exposure to HBV. LPS stimulation alone induced moderate secretion of both IL-1 beta and IL-6 (300 pg/ml). After induction of macrophage differentiation by PMA, THP-1 cells acquired adherence and expressed a higher level of IL-1 beta (up to 2 ng/ml) but did not synthesize IL-6. Treatment of THP-1 cells with PMA and LPS caused the highest production of both IL-1 beta and IL-6 (> 5ng/ml). In vitro exposure of PMA + LPS-stimulated THP-1 cells to HBV resulted in secretion of both HBsAg and preS2Ag which was maintained over 10 days of culture. Southern blot technique was used to study the state of HBV DNA in the cells. Hybridization of non-digested cellular DNA showed only high molecular weight HBV DNA forms. The HindIII restriction pattern revealed bands corresponding to large DNA fragments and the presence of bands at the 3.2 kb position. Under these conditions (PMA + LPS), HBV inhibited the production of IL-1 beta and IL-6 proteins and completely suppressed the IL-1 beta and IL-6 mRNA. Thus, our findings (i) strongly support a relationship between the state of cell differentiation and susceptibility of cells to HBV infection, and (ii) demonstrate that HBV exerts an inhibitory effect on the induction of IL-1 beta and IL-6 genes expression in monocytic THP-1 cells. These results suggest that HBV leads to a fall of pro-inflammatory cytokine production by monocytes/macrophages, which may contribute to impaired host immune response during infection.     

Bone mineral density in thyroxine treated females with or without a previous history of thyrotoxicosis

Alterations in lipid metabolism characterized in major part by a decrease in lipoprotein lipase (LPL) activity in adipose tissue are a central feature of cachexia from chronic infection or malignancy. These metabolic derangements may be mediated in large part through endogenous host proteins produced in response to various pathological stimuli. Differentiation factor/leukaemia inhibitory factor (D-factor) is a cytokine whose functions overlap those of tumour necrosis factor-alpha (TNF), IL-6 and IL-1. Recombinant murine D-factor produced a dose- and time-dependent inhibition of heparin-releasable LPL activity in differentiated 3T3-L1 adipocytes. Although 2-10 fold less potent than recombinant murine TNF, D-factor inhibited LPL activity at concentrations of 1-10 ng/ml. When added together, D-factor and TNF produced a synergistic inhibition of LPL activity. Interleukin 6 (IL-6) was 100-fold less potent than D-factor; 0.1 ng/ml of D-factor or 10 ng/ml of IL-6 caused a 50% inhibition of LPL activity. D-factor and TNF increased IL-6 production in 3T3-L1 cells. Ten ng/ml of D-factor or 1.0 ng/ml of TNF stimulated the release of < 1 ng/ml of IL-6 and inhibited LPL activity to 11 +/- 3% and 3 +/- 2% of control, respectively, whereas 50 ng/ml of recombinant IL-6 was required to decrease LPL activity to 24 +/- 19% of control. TNF produced a marked decrease in LPL mRNA, whereas D-factor had minimal or no effect at doses which inhibited LPL activity almost completely. Western blot analysis of cell extracts showed that TNF caused a greater decrease in LPL protein production than D-factor.2+ with TNF, may contribute to the manifestations of cachexia.     

Serum soluble IL-6 receptor concentrations correlate with stages of multiple myeloma defined by serum beta 2-microglobulin and C-reactive protein

Serum soluble interleukin-6 receptor (sIL-6R) concentrations were measured in 52 patients with multiple myeloma (MM) and 24 normal controls, using a commercially available immunoenzymatic assay kit. Patients were staged according to the Bataille et al. myeloma staging system based on the levels of patients' serum beta 2-microglobulin and C-reactive protein. Twenty-one patients were at stage A of disease, 19 at stage B and 12 at stage C at the time of serum collection for sIL-6R determination. Serum sIL-6R concentrations ranged from 15 to 176 ng/ml with a mean of 64.8 +/- 35.9 ng/ml and a median of 58 ng/ml in the entire group of patients studied. These values were significantly higher than those of 34.4 +/- 13.4 ng/ml found in the controls (P < or = 0.001). Patients of stage C had higher sIL-6R levels (94.8 + 41.2 ng/ml) than patients of stage B (67.7 +/- 31.0 ng/ml) (P < 0.01), and markedly higher than patients of stage A (45.0 +/- 23.1 ng/ml) (P < 0.001). Serum levels of sIL-6R in patients with stage A disease did not differ statistically from those of the controls. A linear positive correlation was observed between serum levels of the receptor and the stage of MM (r = 0.539, P < 0.001). These data strongly suggest that serum sIL-6R concentrations correlate with the stages of MM and may be used as an indicator of the activity of the disease.     

Extramedullary expansion of hematopoietic progenitor cells in interleukin (IL)-6-sIL-6R double transgenic mice

Soluble cytokine receptors modulate the activity of their cognate ligands. Interleukin (IL)-6 in association with the soluble IL-6 receptor (sIL-6R) can activate cells expressing the gp130 signal transducer lacking the specific IL-6R. To investigate the function of the IL-6-sIL-6R complex in vivo and to discriminate the function of the IL-6-sIL-6R complex from the function of IL-6 alone, we have established a transgenic mouse model. Double-transgenic mice coexpressing IL-6 and sIL-6R were generated and compared with IL-6 and sIL-6R single-transgenic mice. The main phenotype found in IL-6-sIL-6R mice was a dramatic increase of extramedullary hematopoietic progenitor cells in liver and spleen but not in the bone marrow. In IL-6 single-transgenic mice and sIL-6R single-transgenic mice no such effects were observed. The high numbers of hematopoietic progenitor cells were reflected by a strong increase of peripheral blood cell numbers. Therefore, activators of the gp130 signal transducer like the IL-6-IL-6R complex may represent most powerful stimulators for extramedullary hematopoietic progenitor cells. gp130 activators may become important for the expansion of hematopoietic progenitor cells in vivo and in vitro.     

Serum interleukin-6 (IL-6) and interleukin-4 (IL-4) in patients with multiple myeloma (MM)

In this study we determined, in patients with multiple myeloma (MM), serum levels of IL-4 and IL-6 at diagnosis and during the course of the disease, seeking a correlation with disease activity and prognosis. We studied 54 MM patients, 41 of whom responded to chemotherapy whilst 11 were resistant. At diagnosis, IL-6 was increased in 66% of patients (median 35.5 pg/ml) whereas IL-4 was low (median 4 pg/ml) in 75% of patients. In responding patients, IL-4 increased in remission (median 25 pg/ml), whereas IL-6 decreased (median 4 pg/ml). In chemotherapy-resistant patients, IL-6 and IL-4 values remained stable during the course of the disease.     

Keratosis follicularis spinulosa decalvans: report of a new pedigree

Soluble interleukin-6 receptor (sIL-6R) has previously been shown to potentiate the activity of interleukin (IL)-6, which may display antitumor activity. We evaluated sIL-6R and IL-6 levels in the sera of 24 patients following transplantation (allogeneic, n=17; autologous, n=7). Five patients developed acute graft-versus-host disease (AGVHD), three had early graft rejection, and three had an early relapse following bone marrow transplantation (BMT). Soluble IL-6R levels were evaluated at day - 10, day 0, day of engraftment, and during BMT-related complications, using IL-6R-specific monoclonal antibodies (mAb) and double-sandwich ELISA. In normal controls, sIL-6R and IL-6 levels were 20+/-3 ng/ml and 0.01+/-0.005 ng/ml, respectively. Soluble IL-6R levels increased in direct correlation with engraftment in the uneventful allogeneic transplants (17.7+/-2.1 ng/ml at day 0 to 49.7+/-2.6 ng/ml at day of engraftment, n=6, P<0.05) as well as in the autologous transplants (26.8+/-2.82 at day 0 to 66.4+/-12.9 at day of engraftment, n=5, P=0.01). In contrast, IL-6 levels declined with time during the conditioning period and showed only a modest elevation following BMT. Increased levels of sIL-6R and IL-6 were found in the patients who developed AGVHD (23.8+/-4.2 and 0+/-0 ng/ml at day 0 to 79+/-6.9 and 0.26+/-0.04 ng/ml, respectively, at time of AGVHD, n=5, P=0.01). No correlation was found between the severity of AGVHD and sIL-6R levels. In the three patients with early relapse, sIL-6R levels increased from 30+/-0 ng/ml at day 0 to 90 ng/ml (P=0.05) and IL-6 levels increased from 0 to 0.16+/-0 ng/ml, respectively. The mean elevation of sIL-6R in the patients with early relapse and AGVHD was significantly higher than the mean elevation in the patients with the relatively smooth engraftment (P<0.05). Contrary to these findings, in the three patients with graft rejection, sIL-6R levels decreased while IL-6 was found to be elevated. Basic disease, conditioning regimen, type of transplant, GVHD propylaxis, and T cell depletion had no effect on sIL-6R or IL-6 levels. In summary, sIL-6R levels positively correlated with engraftment. Both sIL-6R and IL-6 levels were found to be significantly elevated in patients who developed AGVHD or early relapse following BMT. Therefore, the sIL-6R level may be used as a tool for assessing engraftment and transplant-related complications following BMT.     

Purging of mammary carcinoma cells during ex vivo culture of CD34+ hematopoietic progenitor cells with recombinant immunotoxins

Tumor cells have been found in autologous hematopoietic cell transplants used after high-dose chemotherapy. To specifically eliminate contaminating mammary tumor cells during ex vivo expansion of CD34+ hematopoietic progenitor cells, we used recombinant immunotoxins (ITs) directed against cell-surface antigens expressed on mammary carcinoma cells. ITs were expressed from fusion cDNAs combining a single-chain antibody fragment (scFv) directed against the Erb-B2 or epidermal growth factor (EGF) receptors with a truncated Pseudomonas exotoxin A fragment devoid of its cell-binding domain. CD34+ hematopoietic progenitor cells did not express Erb-B2 and EGF receptors as detected by Western blotting. Ex vivo expansion of total hematopoietic cells or of colony-forming cells from CD34+ progenitors in the presence of stem-cell factor (SCF), interleukin-1 (IL-1), IL-3, IL-6, and erythropoietin (Epo) was not affected when ITs were added to the cultures. In contrast, MDA-MB 453 and MCF-7 mammary carcinoma cells were depleted in a dose- and time-dependent manner by more than 3 log in coculture with CD34+ cells over a period of 7 days in the presence of 100 to 1,000 ng/mL of anti-Erb-B2 IT. This included elimination of the subpopulations with regrowth potential. Similarly, addition of either anti-Erb-B2 or anti-EGF receptor ITs to primary breast cancer cells isolated from patients with metastatic disease resulted in elimination of cytokeratin-positive cells in seven of seven samples. ITs are highly efficient and convenient to use for the depletion of mammary tumor cells during ex vivo expansion of hematopoietic progenitor-cell autografts.