Meningeal involvement in multiple myeloma

Meningeal involvement in multiple myeloma is a rare occurrence. We report a case of IgG myeloma with neoplastic cell infiltration into the cerebrospinal fluid as determined by a protein A plaque-forming cell assay. Electrophoresis of the cerebrospinal fluid revealed a monoclonal band in the same position as the monoclonal band in the serum. Meningeal involvement may probably be more common at the terminal stage in multiple myeloma than has been previously considered.

Control of serum protein production in hepatocyte hybridomas: immortalization and expression of normal hepatocyte genes

"Hepatocyte hybridomas" have been isolated after fusion of adult hepatocytes and alpha-fetoprotein (AFP)-producing mouse hepatoma cells. The yield of viable hybrid clones was low but could be increased by culturing the cells in the presence of insulin. On the basis of their chromosome constitution, the hybrids were classified into two groups characterized by either a single or a double set of mouse (hepatoma) chromosomes. The hybrids segregated rat chromosomes and thus constitute an excellent material for gene mapping studies in the rat. Most of the hepatocyte hybridomas retained the production of one or more rat serum proteins, indicating that the corresponding structural genes, contributed by the normal hepatocyte parent, have been immortalized and maintained in the active state after fusion. However, these hybrids do not produce rat AFP, although mouse AFP synthesis is maintained. This result strongly suggests that silent rat (hepatocyte) AFP genes coexist in hepatocyte hybridoma nuclei with active mouse (hepatoma) AFP genes. Finally, on the basis of certain properties of these hepatocyte-hepatoma hybrids, we suggest that the nondividing state of the hepatocytes is actively controlled by a regulatory mechanism which prevents DNA synthesis or entry into mitosis or both.

Presence of a tumour-inhibiting factor (TIF) in sera from normal but not tumour-bearing mice

Some plasmacytomas produce myeloma proteins with known antibody specificities and the secretion of these proteins by individual tumour cells can be determined using haemolytic plaque assay. After a 3 day culture of mouse plasmacytoma cells in medium containing 10% normal mouse serum, the number of plaques was reduced to less than 10% when compared to that of tumour cells incubated with either foetal calf serum or normal rabbit serum. However, tumour cells incubated with sera from mice bearing TEPC-15, McPC-603, or MOPC-315 plasmacytomas displayed control levels of plaques. The production of plaques paralleled the viability of tumour cells suggesting that the reduction of plaque formation is due to the decreased viable cell number. The tumour-inhibiting activity was recovered from the fraction of apparent molecular weight of 300,000-400,000 after a partial purification using an agarose (A 0.5 M) column. This fraction, however, did not suppress in vitro induction of antibody production. Kinetic experiments using sera obtained sequentially from individual mice receiving either TEPC-15 or MOPC-315 plasmacytomas further indicated that the tumour-inhibiting activity is severely reduced during a 2 week period after tumour inoculation. The inhibition of tumour cells did not appear to be specific since tumour cells of three plasmacytomas (TEPC-15, MOPC-167 and MOPC-315), a mastocytoma (P815) and a lymphoma (EL-4) displayed a similar susceptibility to normal serum.

[Translation of MOPC 21 plasmacytoma cell mRNA in a cell-free wheat germ system]

A wheat germ cell-free system was used for translation of kappa-chain IgG1 messenger RNA isolated from mouse plasmacytoma MOPC 21 cells polysomes. The system was optimised for a number of ingredients of the incubation mixture. Incorporation of labelled amino acids in polypeptides was shown as a function of K+, Mg2+, exogenous mRNA concentration and time, mRNA was purificated by two successive oligo (dT)-cellulose chromatographies and two successive sucrose gradient centrifugations or polyacrylamide gel electrophoresis. Different fractions of poly(A)-RNA stimulated protein synthesis 20--30-fold in a wheat germ cell-free system. Analysis of the translation product of 14 and 16S mRNA by SDS-polyacrylamide gel electrophoresis revealed polypeptide comigrating with the authentic L-chain IgG1 and specifically precipitating by an antiserum to mouse IgG and L-chain IgGl (MOPC 21). The 18 and 28S mRNA fractions directed the synthesis of polypeptides with molecular weight up to 50 000 dalton. Immunospecific translation product of the 18 and 28S mRNA contain both L- and H-chains.

Mechanism of effector-cell blockade. I. Antigen-induced suppression of Ig synthesis in a hybridoma cell line, and correlation with cell-associated antigen

A mouse hybridoma cell line, FluIgM-1, which secretes IgM specific for the hapten fluorescein (FLU) was developed to allow detailed analysis of the effector-cell blockade (ECB) phenomenon, in which contact of antibody-forming cells (AFC) with specific antigen results in marked reduction of antibody secretion. Treatment of hybridoma cells with highly substituted FLU conjugates (e.g., Flu20gelatin) resulted in inhibition of plaque formation. The data indicated close parallels with the ECB of normal spleen AFC, both in speed of onset and the dose of antigen required. The inhibition of antibody secretion was confirmed with a biosynthetic-labeling procedure which demonstrated that this was a result of reduced Ig synthesis. The inhibitory effect appeared to be confined to antibody synthesis, in the total protein synthesis, DNA synthesis, and cell-doubling times were unaffected. The association of FLU conjugates with the cells during and following ECB was studied directly using fluorescence microscopy and the fluorescence-activated cell sorter. These experiments showed that FLU conjugates capable of causing blockade aggregated on the cell surface, that the clearance of cell-associated antigen correlated with recovery from ECB, and that at all times when cell associated antigen was detectable, a portion remained bound to the cell surface and was susceptible to enzymatic removal. The latter observations supported previous findings suggesting that ECB was mediated by extracellular antigen. The direct observation of aggregates of antigen on the surface of blockaded cells is consistent with a mechanism involving cross-linking of Ig receptors. Finally, Fc receptors were not present on hybridoma cells, excluding their involvement in induction of ECB.

Identification and characterization of rabbit-mouse hybridomas secreting rabbit immunoglobulin chains

Standard cell-fusion techniques have been used to generate hybrid cells from rabbit spleen cells and mouse myeloma cell lines. The hybrids were selected for secretion of rabbit immunoglobulin. Detailed allotype analyses were carried out for 189 cell lines found to be immunoglobulin positive: 1 produced an intact immunoglobulin molecule with antibody activity, 143 produced rabbit light (L) chains, 36 produced rabbit heavy (H) chains, and 9 cell lines gave negative results in tests for group a and b allotypes. Fusions with a nonproducing murine myeloma cell line (SP-2) yielded only L chain-secreting hybrids, whereas 27% of hybrids resulting from fusion with an L chain-producing line (PU) secreted rabbit H chains paired with mouse L chains. Several of the hybridomas have maintained the ability to produce rabbit immunoglobulin chains in culture for almost 1 year and can be propagated as ascites tumors in athymic (nude) mice. Cytogenetic analyses have detected no rabbit chromosomes in the stable hybrid cell lines.

Amplification of translational control by membrane-mediated events: a pleiotropic effect on cellular and viral gene expression

This review deals with the events which are triggered in tissue culture cells upon exposure to medium hyperosmolarity, to virus infection and to inducers of terminal differentiation. Increased medium osmolarity mimics, in several ways, events which follow infection of cells by cytopathogenic viruses. These are: inhibition of uptake of amino acids, glucose and uridine, the release or activation of a low molecular weight substance which mediates an immediate and specific inhibition of polypeptide chain initiation, and alteration in the phosphorylation state of ribosomal proteins. All these effects appear to be related to or be a consequence of membrane alterations. Similar alterations in transport and protein synthesis are initiated in Friend erythroleukemic cells upon induction of terminal differentiation.

[Isolation and characterization of the matrix properties of electrophoretically homogeneous immunoglobulin L-chain mRNA from mouse myeloma MORC 21]

mRNA with m. w. 4.10(5) dalton was isolated by elution of one of the fractions of poly(A)-RNA from polyacrylamide gel. During reelectrophoresis this mRNA was electrophoretically homogeneous and had the same size. The isolated fraction represented the template activity in a wheat germ cell-free system of protein synthesis and stimulated the synthesis of polypeptides, electrophoretically correspondent to L-chain of authentic immunoglobulin. Comparative data of properties of electrophoretically homogenous mRNA and analogous fraction of mRNA, isolated from sucrose concentration gradient after fractionation of total poly(A)-containing RNA are given.

Type C virus and immunoglobulin A production by murine myeloma MOPC-315: two independent activities

The suspected correlation between cessation of type C virus production and halt in immunoglobulin secretion by murine myeloma cells was studied. Employing two variants of the murine myeloma MOPC-315, immunoglobulin A-producing and nonproducing cells, we demonstrated that the two myelomas release similar levels of type C viruses which share common nucleotide sequences and that the viral genomes are equally expressed within the cells. Thus, the suggested relation between these two activities does not apply for MOPC-315 cells and probably for other murine myelomas also.

Effect of temperature on protein and immunoglobulin synthesis and secretion in two mouse myeloma cell lines

Protein synthesis in differentiated MOPC-21 and MPC-11 mouse myeloma cells was studied to determine the basis for the differences in the temperature and actinomycin D sensitivity of translation between non-differentiated mouse L-cells and differentiated rabbit reticulocytes. The temperature dependence of total protein synthesis was similar to that of L-cells and reticulocytes, being biphasic in Arrhenius plots with apparent activation energies of approximately 25 and 42 kcal/mol, above and below 25 degress C. The dependence of the secretion process was different since it was not biphasic, having a single activation energy of about 22 kcal/mol. Myeloma polysomes were like L-cell polysomes in their response to lower temperature and reached a minimum level of 50% at 15 degress C. This response was also found for the specific polysomes synthesizing the IgG H- and L-chains. In the presence of actinomycin D, myeloma polysomes declined exponentially with a half-life of approximately 6 hours. These two L-cell-like responses were not found in reticulocytes. Translation of both the IgG mRNAs and the non-IgG mRNAs was reduced by lower temperatures and actinomycin D, even though the L-chain mRNA was slightly more resistant, suggesting that this mRNA is slightly more efficient. The results of these experiments suggest that the translational differences between L-cells and reticulocytes are not mRNA dependent, but are cell type differences.

Structural evidence for independent joining region gene in immunoglobulin heavy chains from anti-galactan myeloma proteins and its potential role in generating diversity in complementarity-determining regions

We have determined the variable region sequences of four heavy chains from beta(1-6)D-galactan-binding myeloma proteins. Two of these proteins are identical to position 100 which is located in the third complementarity-determining region (CDR-3). The remaining two differ at a total of 8 positions over the first 100 amino acids, and all of the differences can be explained by single-base mutations at the DNA level. When an assessment is made of the protein segment following CDR-3, which has been termed "J segment" or "FR4," a completely different pattern of variation is observed. The J segments from the four proteins can be divided into two sets. Members of each set share a series of linked amino acids not found in members of the alternative set. The two proteins identical to position 100 have J segments from the two different sets, suggesting that recombination has occurred between V and J genes. An examination of the CDR-3 sequences from the four heavy chains reveals substitutions at positions 100 and 105. Gly is found at 100 in two of the proteins and His in the remaining two. In the two proteins with Gly-100, the following J sequence is limited to one of the two sets of J segments defined by linked amino acids. Similarly, the two heavy chains with His-100 have J segments from the second set. Thus, at the protein level an apparent association is seen between CDR-3 and J segment. If CDR-3 should be found linked to J segment at the DNA level, a new mechanism would be introduced for increasing antibody diversity by recombining various CDR-3 plus J genes with genes coding for the remainder of the variable region. Alternatively, if CDR-3 were coded for by the V gene, then the recombination of V with J may provide an opportunity to introduce mutations in CDR-3. In this case the linkage of amino acids in CDR-3 and the J segments would suggest that recognition signals are used such that certain V genes only pair with a given J gene.

Genetic determination of antibody specificity. Gene translocation and fusion, the molecular basis for the differentiation of the antibody-producing cell

The best system for the study of cell differentiation is a cell which in its differentiated state differs only by one product. This is the case in the immune system. The undifferentiated, but omnipotent stem cell differentiates into a committed B cell which produces only one type of specific antibody out of a million different, genetically fixed possibilities. Gene translocation and fusion is the basis of this differentiation process.

The synthesis and processing of the messenger RNAs specifying heavy and light chain immunoglobulins in MPC-11 cells

The nuclear precursors of the immunoglobulin messenger RNAs of MPC-11 cells were characterized with respect to size, amount per cell and extent of polyadenylation. These cells produce three Ig mRNAs: a 1.8 kb component coding for a gamma2b heavy chain (H mRNA), a 1.2 kb mRNA coding for a k light chain (L mRNA) and a 0.8 kb mRNA coding for the constant region portion of the k light chain (Lf mRNA). To identify the pre-mRNAs without ambiguity, we constructed recombinant DNA plasmids containing H and L cDNA sequences, and used the cloned cDNAs as hybridization probes for analysis of steady state nuclear RNA and in DNA excess hybridization experiments with pulse-labeled nuclear RNA. The nuclear molecules containing Ig sequences consist of an 11 kb component (H1), which we believe to be the primary transcript of the H gene, 5.3 kb (L1), and 3.3 kb (L2) components, which seem to be primary transcripts of the L and L1 genes, components corresponding to mature size H, L and Lf mRNAs, and several intermediate-sized components which include the processing derivatives. The precursor role of these nuclear molecules was established by studies of their labeling kinetics and by appropriate pulse-chase experiments. All the pre-mRNA species including H1, L1 and L2 contain poly(A), thus suggesting that polyadenylation is an early event in the processing of these mRNAs. The MPC-11 cell contains about 30,000 and 40,000 cytoplasmic H and L mRNA molecules, respectively, which must be produced within one cell generation (approximately 24 hr). In comparison, the nucleus contains about 100-150 molecules of total pre-mRNA and only about 10-15 molecules of presumptive primary transcripts for each of these Ig species. These values indicate very rapid transcription rates (greater than 20 transcripts per min) and exceptionally fast processing rates (approximately 0.5 min for the primary transcripts and approximately 5 min for overall nuclear processing) for the Ig mRNAs. Thus rapid transcription and processing, together with high cytoplasmic stability, account for the high abundance of Ig mRNAs in the myeloma cell.

IgG2a-producing variants of an IgG2b-producing mouse myeloma cell line

12 variant cell lines producing an IgG2a (kappa) immunoglobulin derived via different routes from the IgG2b (kappa) synthesizing MPC 11 were studied. These variants all have the parental MPC 11 idiotype as shown by a radioimmunoassay. A comparison of the variants by charge, peptide maps, and assembly patterns has shown that most of them differ from one another, and some can be grouped. One group consists of three primary variants generated with two mutagenic agents: these three have almost indistinguishable peptide maps. Two other primary variants which arose in a similar fashion differ markedly from each other and from this group. A second group is comprised of the four secondary variants which arose from two short heavy chain producing primary variants. Other secondary variants and the one spontaneously arising variant cannot be grouped. Possible genetic mechanisms such as translocation, expression of previously silent genes and recombination are discussed.

Glutamine as a precursor to N-terminal pyrrolid-2-one-5-carboxylic acid in mouse immunoglobulin lambda-type light chains. Amino acid-sequence variability at the N-terminal extra piece of lambda-type light-chain precursors

The mRNA molecules coding for three mouse immunoglobulin lambda-type light (L) chains (MOPC-104E lambda(1), RPC-20 lambda(1), MOPC-315 lambda(2)) programme the cell-free synthesis of precursors larger than the mature proteins. Radioactive amino acid-sequence analyses of each of the three precursors labelled with [(3)H]alanine, [(3)H]serine, [(3)H]glutamine, [(3)H]glutamic acid and [(3)H]threonine showed that an extra piece, at least 18 residues long, is linked to the N-terminus of the mature L-chains. The N-terminal extra-peptide segment may be 19 residues long, since analyses of precursors labelled with [(35)S]methionine indicated an additional N-terminal methionine residue which was recovered in low yields. Presumably this is the initiator methionine, which is known to be short lived in eukaryotes. The mature forms of MOPC-104E, RPC-20 and MOPC-315 lambda L-chains are blocked at the N-termini by pyrrolid-2-one-5-carboxylic acid (pyroglutamic acid). Sequence analyses of precursors labelled with [(3)H]glutamine and [(3)H]glutamic acid showed incorporation only of glutamine in a position that matches with the position of pyrrolid-2-one-5-carboxylic acid in the mature forms of all three precursors, and incorporation of glutamic acid in other positions. The data showed the absence of glutamine-glutamic acid interconversion, since the radioactive peaks obtained from either (3)H-labelled amino acid were discrete, and free from cross-contamination. These results prove that glutamine is the precursor amino acid of pyrrolid-2-one-5-carboxylic acid at the N-termini of the mature MOPC-104E lambda(1), RPC-20 lambda(1) and MOPC-315 lambda(2) L-chains. Thus the formation of pyrrolid-2-one-5-carboxylic acid by cyclization of glutamine is a post-translational event which occurs after, or concomitant with, cleavage of the extra piece from the precursor to yield the mature L-chain. The variable (V) regions (110 amino acid residues) of mouse lambda L-chains are quite similar: when compared with that of MOPC-104E lambda(1) chain, the V-region of RPC-20 lambda(1) chain differs in one residue, and the V-region of MOPC-315 lambda(2) chain differs in 11 residues. The partial sequence data show that the N-terminal extra pieces of the two lambda(1) L-chain precursors have, so far, identical partial sequences; the extra piece of the lambda(2) L-chain precursor differs from these in at least three out of 19 positions.

Immunochemical isolation of gamma-globulin mRNA and estimation of immunoglobulin gene reiteration

The polyribosomes synthesizing gamma-globulin have been isolated by the achievement of specific precipitation using bentonite-treated anti-IgG antibody. The RNA extracted from the immunochemically precipitated polysomes was tested for its ability to direct the synthesis of proteins in a cell-free system. The specific gamma-globulin-synthesizing activity (cpm of gamma-globulin synthesized/microgram RNA) of this RNA was 10-fold greater than that from total polysomes. gamma-globulin mRNA (messenger RNA) isolated by immunoprecipitation was more than 89% pure with respect to contamination by other species of mRNA. The products synthesized by the cell-free system were also analyzed by sodium dodecyl sulphate(SDS)-polyacrylamide gel electrophoresis. This RNA has been hybridized with mouse myeloma DNA. The estimation of immunoglobulin gene reiteration was carried out using hybridization kinetics with consideration given to the DNA/RNA ratio since the estimation from the "half Cot value" is not accurate. The results suggest that in the mouse there are about 20 copies per subgroup of genes coding for the variable region of the H and L chains.

Production of antibodies against influenza virus by somatic cell hybrids between mouse myeloma and primed spleen cells

We have produced somatic cell hybrids between mouse myeloma cells and spleen cells derived from a BALB/c mouse immunized with purified influenza virus. The hybrid cells were found to produce large amounts of antibodies specific for the hemagglutinin of the virus and were able to induce tumor formation when injected into BALB/c mice.