HK1062647B - Method and kit for imaging organs and tissues, using labelled antibodies - Google Patents

Description

The present invention is related to the use of an antibody or antibody fragment which specifically binds a marker produced by or associated with a cell or tissue in an organ of interest, whereby said antibody or antibody fragment is labelled with a magnatic resonance image enhancing agent capable of external detection, and a kit for use in a method of imaging hypoplastic or absent cells or tissues in a mammalian subject.

BACKGROUND OF THE INVENTION 1- Field of the Invention 2- Description of the Prior Art

There is a need for a method that clearly delineates hypoplastic or absent cells or tissues.

It is important in certain clinical situations to detect the presence or absence of particular tissues or organs. Moreover, it is often necessary to determine whether an organ is anatomically correct and whether it has pathology by a non-invasive technique. It would be desirable to have an organ imaging method using organ-specific imaging agents that would make it possible to obtain a "positive" image of the organ, when normal, and a defect in organ visualization if pathology is present. Such a method would provide a new approach to scintigraphic and magnetic resonance imaging of organs and tissues in the body based upon their immunological specificity.

Normal tissues and organs have been imaged by magnetic resonance imaging techniques, but not with the use of imaging-enhancing contrast agents, and not with antibody-conjugated imaging agents.

Methods of imaging tumors and infectious lesions using labeled antibodies and antibody fragments which specifically bind markers produced by or associated with tumors or infectious lesions have been disclosed, inter alia, in Hansen et al., U.S. Pat. No. 3,927,193 and Goldenberg, U.S. Pat. Nos. 4,331,647 , 4,348,376 , 4,361,544 , 4,468,457 , 4,444,744 , 4,460,459 and 4,460,561 , and in related pending applications U.S. Ser. Nos. 609, 607 and 633,999 , See also DeLand et al., J. Nucl. Med., 20, 1243-50(1979).

These methods use radiolabeled antibodies which specifically bind to markers produced by or associated with tumors or infectious lesions, and result in a "positive" image, i.e., uptake of radioactivity attached to the antibody in the structure involved with tumor or infectious lesion and having the appropriate antibody target, thus permitting a visualization of the involved structure. Further improvements in the specificity and resolution of these methods is achieved by the use of various substraction techniques which are also disclosed in the aforementioned references, and which enable background, non-specific radioactivity to be distinguished from specific uptake by the tumor or lesion.

Signore et al. (Advances in Experimental Medicine and Biology, vol. 246, 1988, pages 119 - 125) disclose the use of ¹²³I-labelled IL for in vivo visualization of insulitis.

US patent 4,735,210 discloses the use of a ¹³¹I-labelled antibody directed to the Langerhans cells of the endocrine pancreas for organ scintigraphy of a 3-month old male suspected of having pathology of the endocrine pancreas.

Antibody conjugates comprising organ-specific and tissue-specific antibodies and addends for scintigraphic detection or magnetic resonance image enhancement have not been used as organ imaging reagents.

A need continues to exist for imaging and therapeutic methods which are more sensitive and specific and for organ imaging reagents and methods with high specificity for differentiation of particular organs and tissues from surrounding structures.

OBJECTS OF THE INVENTION

Another object of the invention is to provide organ- and tissue-specific methods and agents for magnetic resonance imaging.

Another object of the invention is to provide reagents and kits suitable for use in the imaging methods of the invention.

The problem underlying the present invention is solved by the subject matter of the independent claims. Preferred embodiments may be taken from the dependent claims.

More specifically, in a first aspect the problem underlying the instant invention is solved by the use of an antibody or antibody fragment which specifically binds a marker produced by or associated with a cell or tissue in an organ of interest, said antibody or antibody fragment being labelled with a magnetic resonance image enhancing agent capable of external detection, in the manufacture of a composition for use in a method of imaging hypoplastic or absent cells or tissues in a mammalian subject suffering from juvenile diabetes by magnetic resonance imaging of islet cells, wherein the amount of the labelled antibody or antibody fragment is to be parenterally injected and is sufficient to permit an enhanced magnetic resonance image of said organ to be obtained.

In an embodiment the antibody or antibody fragment is a Fv, single chain antibody, Fab, Fab' or F(ab')₂ fragment or an intact antibody.

In another embodiment the magnetic resonance image enhancing agent is a species of Gadolinium, Iron, Manganese, Rhenium, Europium, Lanthanium, Holmium, or Terbium.

In still another embodiment, the antibody or fragment, prior to being labelled or conjugated, has a specific immunoreactivity to targeted cells or tissues of at least 60% and a cross-reactivity to other antigens of less than 35%.

In a second aspect, the problem underlying the instant invention is solved by a kit for use in a method of imaging hypoplastic or absent cells or tissues in a mammalian subject suffering from juvenile diabetes by magnetic resonance imaging of islet cells comprising, in a suitable container a targeting antibody or antibody fragment labelled with a magnetic resonance image enhancing agent that specifically binds a marker produced or associated with a hypoplastic or absent cell or tissue in a mammalian subject suffering from juvenile diabetes, whereby the labelled targeting antibody or antibody fragment is parenterally injected.

SUMMARY OF THE INVENTION

In one embodiment, the invention provides an imaging method for positive imaging of an hypoplastic or absent tissue or organ in a mammal. The method comprises the steps of (a) parenterally injecting a mammalian subject, at a locus and by a route providing access to said tissue or organ, with an amount of a magnetic resonance image enhancing agent sufficient to permit an enhanced magnetic resonance image of said structure to be effected; and (b) obtaining an enhanced magnetic resonance image of said structure, at a time after injection of said agent sufficient for said agent to accrete in said structure. The imaging agent comprises an antibody/fragment which specifically binds to said organ or tissue, and which is labeled with a magnetic resonance enhancing agent.

Kits useful for practicing the methods of the invention are also provided.

DETAILED DESCRIPTION OF THE INVENTION

The above methods are beneficial for imaging

1. (1) hypoplastic or absent tissue or organs, in juvenile diabetes, wherein the islet cells of the pancreas can be atrophic or significantly reduced.

The above methods include the use of a growth factor receptor antibody or a hormone receptor antibody to target to end-organs bearing such receptor(s), the functions of which can be blocked with said antibodies.

Many hormone and growth factor receptors are known, and frequently show sufficient organ and tissue proclivity to allow these to serve as targets for antibodies which, when bound to said receptors, affect the function of the tissues and result in an immunological or, by the use of conjugates with drugs, a chemical ablation, or a radiation ablation when used as a conjugate with therapeutic isotopes.

Several methods are known to those skilled in the art for producing organ or tissue associated or specific antibodies, if existing antibodies are considered unsuitable or if different or more discriminating specificities are desired. Generally, whole cells, tissue samples and/or cell or tissue fractions, membranes, antigen extracts or purified antigens are used to challenge the immune system of a suitable animal, e.g., a mouse, rabbit, hamster, goat or the like, the antigen being rendered immunogenic by aggregation if necessary and/or by coadministration with a suitable conventional adjuvant. Hyperimmune antiserum can be isolated and polyclonal antibodies prepared by conventional procedures. Alternatively, spleen cells can be fused with immortal myeloma cells to form hybridoma cells producing monoclonal antibodies, by what are now conventional procedures. See, e.g., the procedures in the above-referenced U.S. Patent Application Serial No. 609,607 for illustrative techniques. Hybridomas using animal, e.g., mouse, or human myeloma cell lines and animal or human spleen or lymph cells are all know in the art, and can be made and used for the present method. See, for example, Glassy et al., "Human Monoclonal Antibodies to Human Cancers", in "Monoclonal Antibodies and Cancer", Boss et al., Eds., 163-170 (Academic Press, 1983). The specific antisera or monoclonals are screened for specificity by methods used to screen the antilymphocyte clones in the references cited hereinabove, which methods are also conventional by now in this art.

Organ-associated and organ-specific antibodies can be developed by immunizing a suitable animal host with certain mammalian tumors or normal organ/tissue extracts and/or cells, as well as with purified hormone receptors or growth factor receptors. It is well known that use of tumors as immunogens can result in antibodies which not only react with neoplasia but also with normal tissue components which sometimes show an organ-restricted nature. Histogenetic and functional differences between various tissues and organs of the body of course suggest that distinct antigens are present and identifiable. A body of scientific literature already exists which claims the identification of organ-specific antigens, either using classical immunization approaches or by immunizing with specific tumors, and this is reviewed by Goldenberg et al., Cancer Res., 3455(1976), showing that such antigens are known and available.

Similar organ- and tissue-associated and specific antigens are identifiable by hybridoma methods which produce monoclonal antibodies. One recent development is the production of human hybridoma monoclonal antibodies by securing lymphocytes or plasma cells from patients showing certain organ-restricted autoimmune diseases, e.g., thyroiditis, gastritis, ulcerative colitis, myositis, and the like. These antibody-producing cells are then fused in vitro with human or murine myeloma cells and hybridomas of appropriate anti-organ and anti-tissue antibody formation are produced and propagated, using well known methods. Also, patients with specific tumor types can be used as a source of such lymphocytes or plasma cells, or such patients can be further immunized with such tumor cells for stimulating the production of anti-organ and anti-tissue antibodies. The lymphatic tissue removed is then used for fusion with suitable myeloma cells, by procedures which are by now well known and conventional in the art.

Organ-associated and organ-specific antigens can be isolated for immunization of another species, e.g., subhuman primates, rodents, rabbits, goats, etc., by a number of methods known in the art, such as isolation of cell membranes or disruption of the cells, e.g., by centrifugation, sonication, etc., to obtain intracellular antigens. It is preferable, for these purposes, to use intracellular as opposed to surface and extracellular antigens. In this manner, organ-associated and organ-specific antigens can be obtained from a large number of tissues and organs of the body, including brain, thyroid, parathyroid, larynx, salivary glands, esophagus, bronchus and lungs, heart, liver, pancreas, stomach and intestines, kidney, adrenal gland, ovary, testis, uterus, prostate, etc. Of further interest is the differentiation of different tissue and cellular components within an organ, such as tubular and glomerular kidney, different regions and cell types of the brain, endocrine and exocrine pancreas, etc., especially by the identification of antigens and antigen epitopes restricted to the individual cell and tissue types in question, as accomplished with polyclonal and/or hybridoma-monoclonal antibody-production methods known in the art.

Antibodies can be produced using cells isolated from tissue obtained at autopsy. For example, mice can be immunized with such tissues for a period necessary to evoke anti-specific organ or tissue antibodies. The spleens of these mice are removed and then fused, by standard methods, with a murine myeloma cell line suitable for hybridoma production. Using methods already standard in the art, monoclonal antibody-producing hybridomas are selected and propagated, and those with organ- or tissue-associated antibody production are cloned and expanded as a source of organ or tissue antibodies. Absolute tissue specificity is not required since significant quantitative differences ordinarily suffice for operational specificity for imaging purposes.

Antibodies and fragments useful in the methods of the present invention include those against antigens associated or produced by normal organs, tissues, and cells, and may or may not be cross-reactive with certain neoplastic tissues.

Preferred are those which, prior to being labeled or conjugated, have a specific immunoreactivity to targeted cells, tissue or organs of at least 60% and a cross-reactivity to other antigens of less than 35%.

Specific examples include antibodies and fragments against pancreatic islet cells.

Antibodies useful in the present invention may be whole immunoglobulin of any class, e.g., IgG, IgM, IgA, IgD, IgE, chimeric or hybrid antibodies with dual or multiple antigen or epitope specificities. It can be a polyclonal antibody, preferably an affinity-purified antibody from a human or an appropriate animal, e.g., a primate, goat, rabbit, mouse or the like. Monoclonal antibodies are also suitable for use in the present method, and are preferred because of their high specificities. They are readily prepared by what are now considered conventional procedures of immunization of mammals with immunogenic antigen preparation, fusion of immune lymph or spleen cells with an immortal myeloma cell line, and isolation of specific hybridoma clones. More unconventional methods of preparing monoclonals antibodies are not excluded, such as interspecies fusions and genetic engineering manipulations of hypervariable regions, since it is primarily the antigen specificity of the antibodies that affects their utility in the present invention. It will be appreciated that newer techniques for production of monoclonals can also be used, e.g., human monoclonals, interspecies monoclonals, chimeric (e.g., human/mouse) monoclonals, genetically engineered antibodies and the like.

Antibody fragments useful in the present invention are F(ab')₂, F(ab)₂, Fab', Fab, Fv and the like, including hybrid fragments. Also useful are any subfragments retaining the hypervariable, antigen-binding region of an immunoglobulin and having a size smaller than a Fab' fragment. This will include genetically engineered and/or recombinant proteins, whether, single-chain or multiple-chain, which incorporate an antigen binding site and otherwise function in vivo as targeting vehicles in substantially the same way as natural immunoglobulin fragments. Such single-chain binding molecules are disclosed in U.S.Patent 4,946,778 . Fab' antibody fragments may be conveniently made by reductive cleavage of F(ab')₂ fragments, which themselves may be made by pepsin digestion of intact immunoglobulin. Fab antibody fragments may be made by papain digestion of intact immunoglobin, under reducing conditions,, or by cleavage of P(ab)₂ fragments which result from careful papain digestion of whole Ig. The fragments may also be produced by genetic engineering.

It should be noted that mixtures of antibodies, and immunoglobulin classes can be used, as can hybrid antibodies. The hybrids can have two different antigen specificities, e.g., one arm binding to one organ antigen and another arm binding to another antigen, or one arm could bind to one epitope on the antigen, and the other arm could bind to another epitope. The foregoing are merely illustrative, and other combinations of specificities can be envisioned that also fall within the scope of the invention.

Hybrid antibody fragments with dual specificities can be prepared analogously to the anti-tumor marker hybrids disclosed in U.S. Pat. No. 4,361,544 . Other techniques for preparing hybrid antibodies are disclosed in, e.g., U.S. Pat. No. 4,474,893 , U.S. Pat. No. 4,479,895 , U.S. Pat. No. 4,714,681 , U.S. Pat. No. 4,474,893 and in Milstein et al., Immunol. Today, 5,299(1984).

For example, Paganelli, Nucl. Med. Commun. 12:211, 1991, disclosed antibody pretargeting procedures, such as using streptavidin-conjugated antibodies, biotinylated antibodies in conjunction with avidin and biotin, bifunctional antibodies, antibody-hapten complexes, and enzyme-conjugated antibodies, in addition to delivering radiation to target cells and tissues by such 2- and 3-step procedures.

When the cell or tissue is pretargeted by a 2- or 3-step procedure, the subject is injected with a first composition comprising, for example, a streptavidin-conjugated antibody, biotinylated antibody to be used in conjunction with avidin and biotin, bifunctional antibody, antibody-hapten complexes, or enzyme-conjugated antibody, wherein the antibody is an antibody or antibody fragment which specifically binds a marker produced by or associated with said cell or tissue. After the first composition accretes at the targeted tissue or cell, a second composition, which bears the desired imaging, therapeutic, cytoprotective or activating principle, is administered. The second composition either activates the first composition or couples with the first composition to produce a desired effect.

When the cell or tissue is pretargeted in a 3-step procedure, the subject is injected with the first composition which comprises biotinylated antibody or fragment, is then injected with a clearing composition comprising an agent to clear circulating biotinylated antibody or fragment, and then injected with the second composition which comprises biotin conjugated with the desired imaging, therapeutic, cytoprotective or activating agent.

When the term "antibody" is used herein, all the above types of antibodies and fragments are included therein.

The use of light and porphyrins in cancer therapy has been reviewed by van den Bergh (Chemistry in Britain, May 1986, Vol. 22, pp. 430-437) and includes reference to the use of monoclonal antibodies conjugated with a photosensitizer for transporting the latter to the tumor. This has been suggested earlier by Oseroff in Photochem. Photobiol. 41:35S, 1985; Mew et al., Cancer Res. 45:4380, 1985; Hasan et al., Immunity to Cancer, II, pp. 471-477, 1989 [Alan R. Liss, Inc. publishers]; and Pelegrin et al., Cancer 67:2529, 1991, which involved tissue culture or animal studies of fluorescent dyes attached to antitumor antibodies.

The imaging agent will normally be administered by injection at a site and by a means that insure that it is mobilized and taken up into the organ or tissue which will vary by the tissue or organ to be imaged.

The agent is preferable injected by a systemic route, e.g., intravenously, intraarterially, intramuscularly or subcutaneously, or by a combination of systemic routes insuring its accretion in the tissue or organ of interest.

Volumes of labeled antibody imaging agent, normally in sterile physiological saline, will normally vary somewhat depending upon the site, the concentration, and the number of injections.

Imaging is normally effected up to about 24 hours, more preferably at about 2 - 6 or less hours after injection of the imaging agent, to obtain the "positive" image of the organ or tissue. Two- and three-step targeting methods will require longer periods.

Timing of injections of imaging agents will depend upon the types of agents and methods used and the targeting patterns to the organs and tissues of interest.

The conjugate will generally be administered as a sterile aqueous solution in a buffered saline. Dosage units of about 1 - 200 mg of conjugate will be administered for a duration of treatment as determined by the skilled practitioner. It may be necessary to reduce the dosage and/or use antibodies from other species and/or hypoallergenic antibodies, e.g., chimeric mouse/human, CDR-grafted ("humanized"), or primate antibodies, to reduce patient sensitivity.

Routes of administration include intravenous, intraarterial, intrapleural, intraperitoneal, intrathecal, subcutaneous or by perfusion.

An application of the organ- or tissue-specific or organ- or tissue-associated antibodies disclosed hereinabove is for normal organ magnetic resonance imaging (mri). In this case, an antibody/fragment bearing a mr image enhancing agent is administered with the intention of obtaining a "positive" image of the organ, when normal, and a defect in organ visualization if pathology is present. This provides a new approach to organ- and tissue-specific nuclear and magnetic resonance imaging of organs and tissues in the body, based upon their immunological specificity.

The method of the invention is practiced with magnetic resonance imaging agents. A combination of these imaging agents can also be used, although this requires more complex instrumentation and data processing.

Magnetic resonance imaging (mri) is effected in an analogous manner to scintigraphic imaging except that the imaging agents will contain magnetic resonance (mr) enhancing species rather than radioisotopes. It will be appreciated that the magnetic resonance phenomenon operates on a different principle from scintigraphy. Normally, the signal generated is correlated with the relaxation times of the magnetic moments of protons in the nuclei of the hydrogen atoms of water molecules in the region to be imaged. The magnetic resonance image enhancing agent acts by increasing the rate of relaxation, thereby increasing the contrast between water molecules in the region where the imaging agent accretes and water molecules elsewhere in the body. However, the effect of the agent is to decrease both T₁ and T₂, the former resulting in greater contrast while the latter results in lesser contrast. Accordingly, the phenomenon is concentration-dependent, and there is normally an optimum concentration of a paramagnetic species for maximum efficacy. This optimal concentration will vary with the particular agent used, the locus of imaging, the mode of imaging, i.e., spin-echo, saturation-recovery, inversion-recovery and/or various other strongly T₁-dependent or T₂-dependent imaging techniques, and the composition of the medium in which the agent is dissolved or suspended. These factors, and their relative importance are known in the art. See, e.g., Pykett, Scientific American, 246, 78(1982); Runge et al., Am. J. Radiol., 141, 1209(1983).

The mr image enhancing agent must be present in sufficient amounts to enable detection by an external camera, using magnetic field strengths which are reasonably attainable and compatible with patient safety and instrumental design. The requirements for such agents are well known in the art for those agents which have their effect upon water molecules in the medium, and are disclosed, inter alia, in Pykett, op. cit., and Runge et al., op. cit.

Preparation of antibodies conjugated to a magnetic resonance image enhancing agent can be effected by a variety of methods. In order to load an antibody molecule with a large number of paramagnetic ions, it may be necessary to react it with a reagent having a long tail to which are attached a multiplicity of chelating groups for binding the ions. Such a tail can be a polymer such as a polylysine, polysaccharide, or other derivatized or derivatizable chain having pendant groups to which can be bound chelating groups such as, e.g., ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid (DTPA), porphyrins, polyamines, crown ethers, bis-thiosemicarbazones, polyoximes, and the like groups known to be useful for this purpose. The chelate is normally linked to the antibody by a group which enables formation of a bond to the antibody with minimal loss of immunoreactivity and minimal aggregation and/or internal cross-linking. Other, more unusual, methods and reagents for conjugating chelates to antibodies are disclosed in copending U.S. Patent Application Serial No. 742,436 to Hawthorne, entitled "Antibody Conjugates", filed June 7, 1985,

MRI contrast agents are well known in the art and include, for example, Gadolinium, Iron, Manganese, Rhenium, Europium, Lanthanium, Holmium, and Terbium.

The mr scans are stored in a computer and the images processed analogously to the scintigraphic data.

The reagents are conveniently provided in kit form, adapted for use in the methods of the invention. Kits will normally contain separate sealed sterile vials of injectable solutions of labeled reagents, or lyophilized antibodies/fragments or antibody/fragment conjugates and vials of sterile conventional injection vehicles with which they will be mixed just prior to administration.

Kits may also include reagents for labeling antibodies, short columns for sizing and/or purification of reagents, and other conventional accessory materials.

Without further elaboration, it is believed that one skilled in the art can, using the preceding description, utilize the present invention to its fullest extent. The following examples are, therefore, to be construed as merely illustrative In the following examples, all temperatures are set forth uncorrected in Celsius; unless otherwise indicated, all parts and percentages are by weight.

REFERENCE EXAMPLES Example 1 - Imaging Pancreatic Cells

Hybridoma-monoclonal antibodies are made in the mouse to the Langerhans cells of the endocrine pancreas, derived from a human autopsy specimum shortly after death. The monoclonal F(ab')₂ reactive against the antigen epitope showing relatively high specificity for Langerhans cells of the pancreas, as demonstrated, e.g., by immunohistology, are labeled with a gamma-emitting isotope, such as with I-123, and injected, e.g. 0.15 mg monoclonal against endocrine pancreas antigen, labeled using Chloramine-T with I-123, at a dose of 3.0 mCi, injected i.v. in a 3-month-old male suspected of having pathology of the endocrine pancreas. External gamma-camera imaging is performed at 6, 24, and 48 hours after injection, without substraction. In this specific case, decreased to almost absent accretion of I-123 radioactivity in the pancreas is suggestive of endocrine pancreas pathology in an infant presenting with pancreas hormone deficiency shortly after birth.

Example 2 - Endometriosis Detection

A woman complains of amenorrhea and infertility and is suspected of having endometriosis. She is injected with 1 mg of anti-endometrial tissue monoclonal antibody Fab' labeled with Tc-99m (20 mCi) intravenously. Four hours later, a total body planar scan reveals abnormal foci of radioactivity in the right lower chest and in the retroperitoneum, which are confirmed by single photon emission computer tomography immediately thereafter. The patient is then referred to ablation therapy.

A woman is diagnosed to have endometriosis and is referred to her gynecologist for treatment. An endometrial tissue-associated monoclonal antibody IgG and a monoclonal antibody IgG against FSH receptor are labeled with I-131 by the chloramine-T method at a specific activity of 10 mCi/mg, and the combination is then infused i.v. to deliver a dose of 100 mCi I-131. After monitoring her peripheral blood cells during the next month, a repeat therapy is given 6 weeks later. After an additional 6 weeks, the patient shows a complete remission of her symptoms.

The preceding examples can be repeated with similar success by substituting the generically or specifically described reactants and/or operating conditions of this invention for those used in the preceding examples.

It will be understood that the invention is not limited to use of known antibodies or markers, but can be practiced with antibodies to any marker produced by or associated with an organ or tissue.

Claims (5)

1. Use of an antibody or antibody fragment which specifically binds a marker produced by or associated with a cell or tissue in an organ of interest, said antibody or antibody fragment being labelled with a magnetic resonance image enhancing agent capable of external detection, in the manufacture of a composition for use in a method of imaging hypoplastic, or absent cells or tissues in a mammalian subject suffering from juvenile diabetes by magnetic resonance imaging of islet cells, wherein the amount of the labelled antibody or antibody fragment is to be parenterally injected and is sufficient to permit an enhanced magnetic resonance image of said organ to be obtained.
2. Use according to claim 1, wherein the antibody or fragment is a Fv, single chain antibody, Fab, Fab', (Fab)₂ or F(ab')₂ fragment or intact antibody.
3. Use according to any one of claims 1 to 2, wherein the magnetic resonance image enhancing agent is a species of Gadolinium, Iron, Manganese, Rhenium, Europium, Lanthanium, Holmium, or Terbium.
4. Use according to any one of claims 1 to 3, wherein the antibody or fragment, prior to being labeled or conjugated, has a specific immunoreactivity to targeted cells or tissues of at least 60% and a cross-reactivity to other antigens of less than 35%.
5. A kit for use in a method of imaging hypoplastic or absent cells or tissues in a mammalian subject suffering from juvenile diabetes by magnetic resonance imaging of islet cells comprising, in a suitable container:

   a targeting antibody or antibody fragment labelled with a magnetic resonance image enhancing agent that specifically binds a marker produced by or associated with a hypoplastic or absent cell or tissue in a mammalian subject suffering from juvenile diabetes,

   whereby the labelled targeting antibody or antibody fragment is parenterally injected.