Multiple chromosomal rearrangements in a spontaneously arising t(6;7) rat immunocytoma juxtapose c-myc and immunoglobulin heavy chain sequences

Spontaneously arising immunocytomas in Lou/Wsl rats contain a consistent translocation between chromosomes 6 and 7. The c-myc gene has been localized to chromosome 7 and has been shown to be rearranged in the majority of the rat immunocytomas. We now report the cloning of the rearranged 11-kilobase EcoRI c-myc fragment from the IgE-secreting IR75 tumor. Sequence analysis revealed that the cytogenetically visible t(6;7) translocation must have involved several events in this tumor. One event has led to the juxtaposition of c-myc and the switch mu region, in a head-to-head orientation. The breakpoint is approximately 850 base pairs upstream from the proximal c-myc promoter on chromosome 7. This area is distinct from the more common mouse plasmacytoma- and Burkitt lymphoma-associated translocation breakpoints and also differs from the known murine retroviral insertion sites. A second rearrangement has led to the transposition of sequences upstream from the switch gamma 1 region to the c-myc-distant end of the switch mu region, tail-to-tail. This requires at least two events, including one inversion. In addition to showing that identical loci (c-myc, immunoglobulin) are juxtaposed via chromosomal translocations in three different tumors (Burkitt lymphoma, mouse plasmacytoma, and rat immunocytoma) in different species (human, mouse, and rat), the multiple rearrangements in IR75 and some other tumors emphasize the selective value of c-myc activation by an immunoglobulin locus in the tumorigenic process.

Generation of agammaglobulinaemic mice by prenatal and postnatal exposure to polyclonal or monoclonal anti-IgM antibodies

Improved experimental conditions are described for the treatment of mice with anti-IgM antibody, which subsequently lead to B-cell deficiency and agammaglobulinaemia. Antibody transmitted via maternal milk alone was found to be more efficient in inducing suppression of serum immunoglobulin isotypes than prenatal transmission or postnatal intraperitoneal injections alone. However, the combined treatment by all three routes of exposure to anti-IgM resulted in total B-cell suppression associated with undetectable levels of all serum immunoglobulin isotypes. Furthermore, suppression of B-cell generation was also achieved with a rat monoclonal mu-specific antibody. The possibility of generating agammaglobulinaemic mice may be useful for investigating the influence of B cells on the generation of T-cell reactivities, and for analysing the effects of monoclonal antibodies in the absence of interfering serum immunoglobulin.

Immunity to lymphocytic choriomeningitis virus in B cell-depleted mice: evidence for B cell and antibody-independent protection by memory T cells

Immunity against lymphocytic choriomeningitis virus (LCMV) in anti-IgM-treated B cell-depleted mice was evaluated. We found that the following immune phenomena were independent of antibodies: the generation of virus-specific cytotoxic T cells; the footpad swelling response against locally injected LCMV; natural killer cell activity basic levels or after LCMV or poly(I) X poly(C) stimulation; immunopathologically mediated LCM after primary intracerebral inoculation; immunological memory in LCMV-immune mice assessed by immune protection against LCM after intracerebrally injected virus or as resistance against the local footpad swelling response to LCMV. This study demonstrates that humoral immunity plays no crucial role in immune protection and immunopathology in murine LCMV infection and suggests that protective memory T cell function is B cell and antibody independent.

Rat monoclonal antibodies. VI. Production of IgA secreting hybridomas with specificity for the 2,4-dinitrophenyl (DNP) hapten

A simple method to obtain rat hybridomas producing specific IgA antibodies is reported. By fusing the IR983F rat myeloma cell line with mesenteric lymph node cells from LOU/C rats immunized via the Peyer's patches with DNP-Salmonella typhimurium, twenty hybrids secreting monoclonal IgA antibodies specific for DNP were produced and maintained as highly secreting transplantable ascitic tumors. The monoclonal IgA antibodies were easily purified by affinity chromatography on a DNP-immunosorbent and were found to comprise both monomers and polymers.

Lymphocyte disappearance and reappearance after a single whole-body irradiation dose of 5 Gy

The effects of a single exposure to 5 Grays of caesium gamma rays administered at a high-dose rate were investigated in rat lymphocyte populations. Such a dose completely depleted the B-cell population but never totally depleted the T-cell population. T and B lymphocytes reappeared in the spleen after 10-15 days and somewhat later in the mesenteric lymph nodes and Peyer's patches. In the spleen, non-circulating B lymphocytes of the marginal zone reappeared after a few days, as did the B lymphocytes of the follicles. Lymphoid tissues were observed to have recovered their normal aspect between days 50 and 60 after irradiation; however, even at that time, the germinal centres had not yet returned to normal.

Rat (and mouse) monoclonal antibodies. V. A simple automated technique of antigen purification by immunoaffinity chromatography

A technique to automate the purification of antigens by immunoaffinity chromatography is described. It is operated on a time basis and measurements of the optical density of the immunoaffinity column eluate are made at 280 nm. Immunoaffinity columns of Sepharose 4B coupled mouse or rat monoclonal antibody can be used for 150 or more cycles. From 23 to 120 mg of monoclonal antibody were purified per run. There is a potential application of this system to other forms of affinity chromatography.

Studies of long-term continuous irradiations using daily doses ranging from 0.07 to 0.30 Gy on the B lymphoid system of the rat

The effects of a continuous exposure to cobalt gamma rays administered to rats at a daily dose of 0, 0.07, 0.12, 0.20 or 0.30 Gy for a period of up to 90 or 135 days, have been observed on their B lymphocyte populations and on their immunoglobulin serum levels. The effects increase with the daily dose and the duration of irradiation. At a daily dose of 0.07 Gy, no clear effect was observed. The depletion was almost negligible after 30 days at a daily dose of 0.12 Gy, but visible after all other doses and durations. However, a clear difference in susceptibility was observed between the marginal zone B compartment and the follicular one, the former being much more affected by the radiation than the second.

Genetic control of the resistance to spontaneous immunocytoma (plasmacytoma-IR tumour) development in LOU/C rats

Immunocytomas (immunoglobulin secreting tumours) appear with a highly spontaneous incidence in animals of the inbred LOU/C strain but never in those of the inbred OKA strain. Congenic rats with LOU/C genetic background, having either the heavy or the kappa light immunoglobulin chain loci from the OKA strain, have an immunocytoma incidence similar to that of the LOU/C strain. The congenic strain, having the major histocompatibility complex of the OKA strain on the LOU/C background, showed no immunocytoma incidence. These results indicate that the MHC locus of the rat, or a gene closely linked to it, determines resistance to immunocytoma development. Specific chromosomal translocation associated with Ig gene chromosome and c-myc play a major role in the origin of the rat IR tumours. These experiments show that the resistance of the OKA strain to the appearance of IR tumours is not correlated with special properties of Ig heavy and kappa gene segments.

Is there a functional heterogeneity among IgE-type mast-cell-sensitizing antibodies?

It has recently been established that mast cells display functional heterogeneity. The question then arises whether the IgE-type of antibody, which avidly binds to and thereby sensitizes mast cells and basophils for allergen-induced release of mediators, also expresses functional heterogeneity. In the present article we bring together several experimental observations, mainly from the rat system, which are difficult to explain unless one postulates that mast cell/basophil-sensitizing antibodies of the IgE-type are heterogeneous in their cell-binding properties.

Fc epsilon receptors on rat B-lymphocytes: specificity and binding kinetics

The binding kinetics of radiolabelled rat IgE to Fc epsilon receptors (R) of rat B-cells have already been studied in IgE-stimulated animals. The receptors expressed after Nippostrongylus brasiliensis infection or 2 injections of 5 mg IgE/100 g body wt were class-specific: IgE binding was not hindered by rat IgM, IgD, IgA, IgG1, IgG2a, IgG2b and IgG2c in immunocompetitive-binding assays. The rat B-cell Fc epsilon R were not species-specific, since mouse IgE competes with rat IgE for binding to these receptors. The apparent number of Fc epsilon R on rat mesenteric lymph node B-cells varied with temp and was 1.1-2.4 X 10(5) at 4 degrees C and 5.9-7.7 X 10(5) at 37 degrees C. The experimental Ka was not influenced by temp and had an average value of 1.38 X 10(8) M-1. At 4 degrees C the IgE binding to B-cell Fc epsilon R had an association rate of 4.9 X 10(3) M-1 sec-1 and a dissociation rate of 4.65 X 10(-5) sec-1. After a very strong stimulation produced by injecting 5 mg IgE/100 g body wt every 24 hr for 5 days, the equilibrium binding curve became diphasic, indicating a probable heterogeneity of the B-cell Fc epsilon R.

Fc gamma receptors on rat eosinophils: isotype-dependent cell activation

Fc receptors for rat IgG subclasses (IgG2a, IgG2c, and IgG1) were studied on rat eosinophils by rosette formation with erythrocytes coated with monoclonal immunoglobulin (Ig) or anti-Ig antisera in a reverse assay. Inhibition experiments revealed that IgG2a and IgG2c bind to the same receptor (IgG2a/IgG2c Fc receptor), distinct from the receptor for IgG1. In addition to the recent demonstration of the blocking effect of IgG2c antibodies in immunity to schistosomes, the present results show that the existence of this common receptor led to the specific inhibition by IgG2c of IgG2a-mediated eosinophil peroxidase release. Kinetic experiments on Schistosoma mansoni-infected rat eosinophils indicate that the IgG2a/IgG2c Fc receptors were occupied by cytophilic antibodies of the IgG2a isotype during the early phase of infection and by IgG2c thereafter. By rosette experiments it was possible to displace both in vivo and in vitro cytophilically bound IgG2a from its receptor. These results confirm, therefore, the major role played by antibodies in the modulation of eosinophil effector function during schistosomiasis. They underline, moreover, the possible isotypic regulation of cell activation.

Fc gamma receptors on rat eosinophils: isotype-dependent cell activation

Fc receptors for rat IgG subclasses (IgG2a, IgG2c, and IgG1) were studied on rat eosinophils by rosette formation with erythrocytes coated with monoclonal immunoglobulin (Ig) or anti-Ig antisera in a reverse assay. Inhibition experiments revealed that IgG2a and IgG2c bind to the same receptor (IgG2a/IgG2c Fc receptor), distinct from the receptor for IgG1. In addition to the recent demonstration of the blocking effect of IgG2c antibodies in immunity to schistosomes, the present results show that the existence of this common receptor led to the specific inhibition by IgG2c of IgG2a-mediated eosinophil peroxidase release. Kinetic experiments on Schistosoma mansoni-infected rat eosinophils indicate that the IgG2a/IgG2c Fc receptors were occupied by cytophilic antibodies of the IgG2a isotype during the early phase of infection and by IgG2c thereafter. By rosette experiments it was possible to displace both in vivo and in vitro cytophilically bound IgG2a from its receptor. These results confirm, therefore, the major role played by antibodies in the modulation of eosinophil effector function during schistosomiasis. They underline, moreover, the possible isotypic regulation of cell activation.

Purification and characterization of a saliva-interacting cell-wall protein from Streptococcus mutans serotype f by using monoclonal-antibody immunoaffinity chromatography

A rat monoclonal antibody, LO SM2, of the immunoglobulin M class, specific for a saliva receptor (SR) from Streptococcus mutans serotype f, was able to precipitate the SR from crude cell-wall-associated antigens (WEA) of this bacteria in presence of a detergent mixture. We have then used the technique of monoclonal-antibody immunoaffinity chromatography to purify the S. mutans SR. Pure SR was obtained from a crude WEA fraction with a single chromatographic step. The active SR could be eluted from the column in a highly purified form with 0.2 M-glycine/HC1, pH 2.8. The final yield was about 32% in terms of binding activity. Characterization of the SR by crossed immunoelectrophoresis, sodium dodecyl sulphate- or 4-30%-native-gradient-polyacrylamide-gel electrophoresis showed that the receptor is a single polypeptide chain of Mr approx. 74000. Native or denaturated forms of the SR adsorbed on to a solid support, such as nitrocellulose, are recognized by monoclonal antibody LO SM2, and both forms are still able to bind the ligand, saliva.

Rat monoclonal antibodies. IV. Easy method for in vitro production

A simple technique for in vitro production of monoclonal antibodies is described. Two to 5 X 10(6) hybridoma cells are diluted in 300 ml of medium in a 2 litre 'roller bottle' and incubated for 2 weeks without subsequent adjustment of the cell concentration or renewal of the medium. The method is based on the observation that when hybridoma cell cultures are maintained in the same medium, although cell growth stops after a few days and the percentage of dead cells increases rapidly, the amount of monoclonal antibody present in the culture medium increases up to the 15th day, the yield reaching more than 10 mg per flask. The method can be used both for rat and mouse hybridoma cell culture.

Rat monoclonal antibodies. III. A simple method for facilitation of hybridoma cell growth in vivo

Hybridoma cells that did not grow when injected subcutaneously or intraperitoneally in histocompatible or Rnu/Rnu rats were injected intravenously into histocompatible recipients. Eight of the 9 cell lines injected in this way grew in several organs of the recipient 3-7 weeks later. Hybridoma cells proliferated mainly in the liver. When the liver homogenate of these animals was injected intraperitoneally into histocompatible recipients, hybridoma cells grew readily giving rise to ascites containing the expected monoclonal antibody for 6 of the 9 cell lines.

Selective depression of thymus-independent anti-DNP antibody responses induced by adult but not neonatal splenectomy

The effect of splenectomy was assessed on rats' capacity to respond to 2,4-dinitrophenol (DNP) conjugated to spider crab haemocyanin (MSH) or hydroxyethyl starch (HES). The response to DNP-HES was profoundly suppressed in all immunoglobulin classes and subclasses by adult splenectomy. This loss of responsiveness increased with time after removal of the spleen. By contrast no significant effect on the anti-DNP-MSH response was caused by splenectomy. Experiments in congenitally athymic rats confirmed the thymus dependency of anti-DNP antibody responses of all classes and subclasses induced by DNP-MSH. DNP-HES responses, however, were elevated in athymic animals. The effect of adult splenectomy in these animals was considerably less than that produced in euthymic rats. Neonatal splenectomy in euthymic rats only resulted in minor impairment of these rats' capacity to respond to DNP-HES as adults, indicating the ability of rats to compensate after neonatal but not adult splenectomy. These data are taken to show that the spleen plays an important role in responses against this thymus-independent type II antigen which is only partially replaceable by other compartments of the immune system.

Extracellular release of rat eosinophil peroxidase (EPO) I. Role of anaphylactic immunoglobulins

The release of intracellular peroxidase (EPO) was investigated in order to evaluate rat eosinophil activation by various immunoglobulin (Ig) isotypes. After successive incubations with purified rat IgG1, IgG2a, IgG2b, IgG2c, IgE, or IgM and their respective anti-Ig antisera, eosinophils released significant amounts of EPO (up to 26% of the intracellular content) only in the case of Ig with anaphylactic activities (IgG2a and IgE). Other classes and subclasses were unable to induce EPO exocytosis. Selective depletion and reconstitution experiments suggested that mast cells were not required in this process. Similar levels of EPO could be released after interaction of eosinophils with antigen-antibody complexes (IgG2a monoclonal antibody and Schistosoma mansoni antigen) immobilized on nonphagocytosable surfaces. These results indicate that EPO exocytosis can be obtained after cell activation with specific antibodies, and that this mechanism is independent of phagocytosis. A kinetic study of eosinophils from S. mansoni-infected rats revealed that IgG2a and IgE cytophilic antibodies induced EPO release after incubation with either specific antisera or specific antigen, which suggests the in vivo relevance of such findings. The present work underlines the parallelism of interaction of anaphylactic-type Ig with eosinophils and with mast cells. Moreover, EPO release seems to represent an interesting marker of eosinophil activation, because close relationships were established between the present findings and previous work on the effector function of rat eosinophils.

Nippostrongylus brasiliensis infection can induce IgE production in rnu/rnu rats

Although rnu/rnu homozygous athymic rats are generally considered to be entirely deficient in mature T cells and unable to produce any T-cell-dependent immune response, we were able to induce slight IgE production in some Nude rats after Nippostrongylus brasiliensis infection. This report stresses the importance of taking the greatest care in the use of congenitally athymic rnu/rnu rats, as strong stimulation can, in some individuals, induce reactions which are generally considered to be T-cell-dependent. Hypotheses explaining this phenomenon are suggested.