Spleen RNA Research Articles

Sequence of a cDNA encoding the β 4 subunit of murine integrin

A cDNA coding for the β 4 subunit of murine integrin (mβ 4) has been cloned and sequenced using mRNA from a murine lung carcinoma as the template. The 5' sequence contains two AUG codons, the second of which initiates synthesis of the mature protein. The cDNA sequence has an open reading frame coding for 1748 amino acids (aa), including a signal peptide, cysteine-rich region, serine- and threonine-rich region, transmembrane domain, and a cytoplasmic domain of over 1000 aa. Overall, the deduced mβ4 aa sequence has 88% identity with the human β 4 subunit (hβ 4) sequence deduced from the sequence of placental mRNA. Reverse transcriptase-polymerase chain reaction using primers flanking splice sites for two variant forms of hβ 4 transcripts provided evidence for alternate splicing of RNA in the murine spleen and to a lesser extent in the skin, uterus, and thymus but was found at only one of the two alternative sites. Five potential glycosylation sites present in the extracellular domain of hβ 4 are conserved in mβ 4. One tyrosine in the terminal region of the cytoplasmic domain (position 1600) is conserved between mβ 4 and hβ 4 and has the consensus sequence for tyrosine phosphorylation. Finally, a genomic restriction map of mβ 4 shows that the gene is about 40 kb in length. No restriction-fragment length polymorphisms were detected between BALB/c liver and BALB/c lung carcinoma DNA.

Use of the most JH-proximal human Ig H chain V region gene, VH6, in the expressed immune repertoire.

VH6, the most 3' human H chain V region gene, is preferentially expressed in the preimmune repertoire of the developing human fetus. To determine whether VH6 contributes to the immune repertoire, we amplified and sequenced from human spleen RNA VH6 rearrangements that were isotype-switched to IgG. Eighteen distinct in-frame VH6 clones were sequenced. Definitive assignment to C gamma 1 could be made in the majority of clones, and all had undergone extensive somatic hypermutation in the V region with an average of 14 (range, 2 to 25) mutations/281 bp in the VH6 segment. The overall frequency of somatic mutation was 5.2% of the total nucleotides sequenced. Replacement somatic mutations were targeted to the complementarity determining region, and the complementarity determining region had higher replacement to silent mutation ratios, consistent with antigenic selection. Silent somatic mutations were also significantly more frequent in the complementarity determining region compared to the framework region. Five clones were derived from the same VH6Dxp'1JH6 rearrangement, each containing unique and shared mutations. All DH segments used by independently arising clones were unique, and all DH reading frames were seen. N segments were lacking at either the 5'DH-JH junction or the 3'DH-JH junction in 7 of 13 independent rearrangements. DH-DH recombinations were frequently observed, and there was biased usage of JH3b and JH4b in the clones. The data imply that a high degree of diversity arises from use of this 3'-VH gene in the immune repertoire.

Cloning and sequencing of rat liver cDNAs encoding the regulatory protein of glucokinase

cDNAs encoding the rat liver regulatory protein of glucokinase were cloned and sequenced. The deduced protein contains 568 amino acids for a molecular mass of 62,867 Da. Northern blot analysis showed the presence of a major RNA species of 2.35 kb in rat liver. No signal was observed with muscle, brain, heart, testis, intestine or spleen RNA. Recombinant regulatory protein expressed in Escherichia coli was insoluble and inactive, and was presumably contained in inclusion bodies. Western blot analysis showed that the recombinant protein was recognized by antibodies raised against regulatory protein purified from rat liver.

Regulation of interleukin 6 gene expression in rat.

The effects of ip endotoxin administration on interleukin 6 (IL6) transcripts in brain and in peripheral tissues of rats were studied together with the effects of this treatment on IL6 and corticosterone concentrations in blood serum. Northern blot analyses showed a rapid increase of IL6 transcripts in spleen, pituitary gland, and adrenals that was paralleled by pronounced elevations in serum IL6 and corticosterone levels. Adrenalectomy further enhanced the induction of IL6 messenger RNA (mRNA) in spleen and pituitary gland and augmented the increase in serum IL6 bioactivity after lipopolysaccharide (LPS) injection. Corticosterone pretreatment (10 mg/kg) completely blocked the increase of IL6 in serum and IL6 mRNA in spleen, adrenals, and hypophysis. In several brain areas, low amounts of IL6 mRNA were detected under basal, noninflammatory conditions, but in response to LPS there was no change in the IL6 mRNA in hippocampus, hypothalamus, and cerebellum. Neither adrenalectomy nor peripheral injections of sublethal LPS doses of up to 10 mg/kg were capable of increasing IL6 mRNA in the hippocampus. The data do not support the hypothesis that central IL6 biosynthesis via transcription of the gene contributes to the endotoxin-mediated activation of the hypothalamic-pituitary-adrenal system. The results, however, clearly demonstrate that LPS-induced IL6 gene expression is subject to glucocorticoid suppression in peripheral tissues.

Isolation of germinal centerlike events from human spleen RNA. Somatic hypermutation of a clonally related VH6DJH rearrangement expressed with IgM, IgG, and IgA.

12 rearranged human VH6 immunoglobulin heavy chain genes arising from the same rearrangement were isolated without preselection from the RNA of a fragment of human spleen. The 12 clones were isolated from a pool of 31 unique VH6 clones arising from 18 unique rearrangements. 2 of the 12 related clones were expressed with IgM, 2 with IgG, and 8 with IgA1. All the clones, including those expressing IgM, showed extensive somatic mutation of germline bases (5.6%), which was consistent with antigen-driven activation of these VH6-expressing clones with recruitment into the immune repertoire. On the basis of significant sharing of somatic mutations between the IgM clones and clones expressing the other isotypes (six mutations shared with IgG clones and eight mutations shared with IgA clones), it was apparent that the IgM-expressing precursor in this diversified family had undergone extensive antigen-driven somatic mutation prior to isotype switching. This family of related clones suggests that a germinal centerlike event had been sampled. The highly mutated IgM clones suggest that there may exist memory B cells capable of further somatic mutation and differential isotype-switching depending on the specific antigenic stimulus.

Cloning and characterization of a novel zinc-finger protein-encoding cDNA from the mouse eye lens

Zinc fingers (Zf) are a common structural motif found in many nucleic acid-binding proteins. In an effort to identify potential transcription factors in the mouse eye lens, we have isolated a Zf-containing clone from a newborn mouse lens cDNA library. The clone, named pMLZ-4, is 4.5 kb in length and contains an open reading frame of 1073 bp. The putative pMLZ-4 protein consists of a short, N-terminal acidic domain followed by twelve tandemly arrayed Zf of the C 2H 2 variety. The remaining 3.2 kb of the cDNA comprises the 3'-untranslated region. PCR analysis detected the presence of pMLZ-4 RNA in liver, heart, kidney, spleen and brain of newborn mice. Hybridization of pMLZ-4 to genomic DNA from a number of species of vertebrates revealed the presence of homologous sequences only in mouse and rat. Unexpectedly, the probe also hybridized to a single band in yeast DNA digested with EcoRI. NIH3T3 cells were stably transformed with a construct that over-expresses the pMLZ-4 mRNA. The stably transformed cells did not differ in appearance from untransformed cells, and an analysis of proteins from transformed and untransformed cells failed to detect any differences resulting from over-expression of the pMLZ-4 mRNA.

Molecular cloning of a cDNA encoding the “61-kDa” calmodulin-stimulated cyclic nucleotide phosphodiesterase. Tissue-specific expression of structurally related isoforms.

We have isolated a 2287-bp cDNA encoding the 61-kDa calmodulin-stimulated cyclic nucleotide phosphodiesterase (CaM PDE) from a bovine brain library. A large open reading frame within the cDNA encodes a 530-residue polypeptide which is identical to the sequence of the purified protein previously determined by direct amino acid sequencing. Moreover, COS cells transfected with the cDNA express a cAMP and cGMP hydrolytic activity that is stimulated by calcium and calmodulin, confirming that the cDNA represents a mRNA species encoding a CaM PDE isozyme. RNase protection analyses indicate that either 61-kDa CaM PDE mRNA or structurally related transcripts encoding different CaM PDE isoforms are expressed in a tissue-specific manner. Total RNA isolated from brain (cerebral cortex, basal ganglia, hippocampus, cerebellum, and medulla/spinal cord), heart, aorta, liver, kidney outer medulla, kidney papilla, trachea, and lung completely protected a 410-base antisense riboprobe corresponding to sequence encoding a portion of the catalytic domain. Little or no protection was detected using adrenal cortex, adrenal medulla, liver, kidney cortex, spleen, or T-lymphocyte total RNA. Only brain RNA completely protected a 240-base antisense riboprobe corresponding to the 61-kDa CaM PDE amino terminus encompassing a putative calmodulin-binding domain. However, heart, aorta, liver, kidney, trachea, and lung RNA protected 150 bases of this riboprobe suggesting that these tissues express an isoform structurally related to the 61-kDa CaM PDE. Northern analysis of mRNA isolated from brain, heart, aorta, liver, kidney, lung, and trachea revealed that the cDNA hybridizes with a 3.8- and a 4.4-kb (kilobase) mRNA species. Interestingly, Northern blots of bovine cerebral cortex and heart mRNA probed under stringent conditions with antisense transcripts corresponding to either the 5'- or 3'-untranslated sequence of the 61-kDa CaM PDE cDNA hybridized with only the 4.4-kb mRNA from both tissues. Since different, yet structurally similar CaM PDE isoforms are expressed in brain and in heart, this result, in addition to the RNase protection data, is consistent with the idea that the mRNAs encoding these two CaM PDE isoforms are products of an alternately spliced gene.

Evolution of vertebrate IgM: complete amino acid sequence of the constant region of Ambystoma mexicanum mu chain deduced from cDNA sequence.

cDNA clones coding for the constant region of the Mexican axolotl (Ambystoma mexicanum) mu heavy immunoglobulin chain were selected from total spleen RNA, using a cDNA polymerase chain reaction technique. The specific 5'-end primer was an oligonucleotide homologous to the JH segment of Xenopus laevis mu chain. One of the clones, JHA/3, corresponded to the complete constant region of the axolotl mu chain, consisting of a 1362-nucleotide sequence coding for a polypeptide of 454 amino acids followed in 3' direction by a 179-nucleotide untranslated region and a polyA+ tail. The axolotl C mu is divided into four typical domains (C mu 1-C mu 4) and can be aligned with the Xenopus C mu with an overall identity of 56% at the nucleotide level. Percent identities were particularly high between C mu 1 (59%) and C mu 4 (71%). The C-terminal 20-amino acid segment which constitutes the secretory part of the mu chain is strongly homologous to the equivalent sequences of chondrichthyans and of other tetrapods, including a conserved N-linked oligosaccharide, the penultimate cysteine and the C-terminal lysine. The four C mu domains of 13 vertebrate species ranging from chondrichthyans to mammals were aligned and compared at the amino acid level. The significant number of mu-specific residues which are conserved into each of the four C mu domains argues for a continuous line of evolution of the vertebrate mu chain. This notion was confirmed by the ability to reconstitute a consistent vertebrate evolution tree based on the phylogenic parsimony analysis of the C mu 4 sequences.

Proopiomelanocortin gene expression in a distinct population of rat spleen and lung leukocytes

Existence of proopiomelanocortin (POMC) messenger RNA (mRNA) and related peptides in extrapituitary sites has been demonstrated in immune cells, although the particular type of immune cell has been the source of considerable debate. Specifically, double labeling studies have shown that POMC peptide expressing cells in the spleen represent a subpopulation of red pulp macrophages, while splenic lymphocyte areas are POMC negative. In addition, it has also been reported that peripheral blood leukocytes express the POMC gene. Using a sensitive solution hybridization technique with a POMC exon-1 RNA probe, we detected 70 +/- 20 fg and 65 +/- 5 fg POMC mRNA per microgram total RNA in whole spleen and lung, respectively, approximately 20,000-fold lower concentrations than found in the neurointermediate lobe of the pituitary. The presence of nuclease protected full length exon-1 bands, rather than the 5' truncated POMC RNAs seen in many nonpituitary tissues, indicates transcription initiation at the normal pituitary POMC promoter site in lung and spleen. In order to localize POMC gene expression in these tissues we employed an in situ hybridization method. There was an intense signal in a small population of large mononuclear cells scattered throughout the splenic red pulp and lung parenchyma. In the lung, these cells were concentrated in the periarteriolar zone in a manner suggestive of migration from the intravascular lumen. These cells had a histomorphology suggestive of monocyte-macrophages. POMC mRNA was undetectable in the splenic white pulp and bronchus-associated lymphoid tissue, indicating an absence of POMC gene expression in splenic and lung lymphocytes. Immunocytochemical studies suggested that POMC-positive cells made up a subpopulation of cells expressing the rat monocyte-macrophage markers ED1 and ED2. Similarly, the distribution of Jenner-Giemsa stained monocyte-macrophages appeared to overlap with POMC positive cells. Studies with anti-rat beta-endorphin antisera revealed scattered cells in the splenic red pulp and lung parenchyma, suggesting that the POMC mRNA is translated in these cells. In summary, POMC mRNA is expressed in a small population of monocyte-macrophage-like cells in lung and spleen but not in lymphocytes in these tissues.

A trophoblast cell line isolated from the ends of elongated pig blastocysts secretes a monocyte/macrophage growth activity

In order to isolate new subtypes of P2Y purinoceptors, a human placenta cDNA library was screened at middle stringency with a P2Y4probe. The purification and the sequencing of several clones led us to identify a 984 base pair open reading frame encoding a new human P2Y receptor. It appeared later that this sequence corresponds to the human ortholog (88% amino acid identity) of the rat receptor recently cloned by Chang et al (J. Biol. Chem.270,26152–26158, 1995) and called P2Y6. Northern blot analysis detected human P2Y6receptor messenger RNA in human spleen, placenta, thymus, intestine, and blood leukocytes. In 1321N1 cells stably expressing the human P2Y6receptor, the formation of IP3was stimulated by nucleotides with the following order of potency: UDP>5-bromo-UPT>UTP>ADP>2-methylthio-ATP>ATP. The P2Y6receptor, together with the previously cloned P2Y4subtype (Communi et al.,J. Biol. Chem.,270,30849–30852, 1995), belongs thus to a subfamily of pyrimidinoceptors inside the P2Y family.

Proopiomelanocortin gene expression in a distinct population of rat spleen and lung leukocytes.

Existence of proopiomelanocortin (POMC) messenger RNA (mRNA) and related peptides in extrapituitary sites has been demonstrated in immune cells, although the particular type of immune cell has been the source of considerable debate. Specifically, double labeling studies have shown that POMC peptide expressing cells in the spleen represent a subpopulation of red pulp macrophages, while splenic lymphocyte areas are POMC negative. In addition, it has also been reported that peripheral blood leukocytes express the POMC gene. Using a sensitive solution hybridization technique with a POMC exon-1 RNA probe, we detected 70 +/- 20 fg and 65 +/- 5 fg POMC mRNA per microgram total RNA in whole spleen and lung, respectively, approximately 20,000-fold lower concentrations than found in the neurointermediate lobe of the pituitary. The presence of nuclease protected full length exon-1 bands, rather than the 5' truncated POMC RNAs seen in many nonpituitary tissues, indicates transcription initiation at the normal pituitary POMC promoter site in lung and spleen. In order to localize POMC gene expression in these tissues we employed an in situ hybridization method. There was an intense signal in a small population of large mononuclear cells scattered throughout the splenic red pulp and lung parenchyma. In the lung, these cells were concentrated in the periarteriolar zone in a manner suggestive of migration from the intravascular lumen. These cells had a histomorphology suggestive of monocyte-macrophages. POMC mRNA was undetectable in the splenic white pulp and bronchus-associated lymphoid tissue, indicating an absence of POMC gene expression in splenic and lung lymphocytes. Immunocytochemical studies suggested that POMC-positive cells made up a subpopulation of cells expressing the rat monocyte-macrophage markers ED1 and ED2. Similarly, the distribution of Jenner-Giemsa stained monocyte-macrophages appeared to overlap with POMC positive cells. Studies with anti-rat beta-endorphin antisera revealed scattered cells in the splenic red pulp and lung parenchyma, suggesting that the POMC mRNA is translated in these cells. In summary, POMC mRNA is expressed in a small population of monocyte-macrophage-like cells in lung and spleen but not in lymphocytes in these tissues.

Two Types of Murine CD34 mRNA Generated by Alternative Splicing

AbstractTo characterize and clarify the function of CD34 antigen experimentally, we isolated two types of CD34 mRNA from a cDNA library of murine stromal cell line, PA-6 stimulated with lipopolysaccharide (LPS) and 12-o-tetra-decanoylphorbol 13-acetate (TPA) using a human CD34 probe. In addition to the clone (open reading frame [ORF]:1149bp) reported by Brown et al, a novel clone (ORF:978 bp) was obtained. The difference between the two clones was in the cytoplasmic portion of CD34; the former has 73 amino acids, while the latter has 16. We investigated the genomic sequence of cytoplasmic portion and found conserved nucleotide sequences at the exon-intron junction (GT…AG). Thus, it was concluded that alternative splicing gave two types of CD34 mRNA. A novel clone contains the longer cDNA, including a insert of 156 bp, but results in a shorter predicted coding sequence because of the introduction of an inframe stop codon. Northern blot analysis using a murine cDNA probe (Hindlll fragment, 900 bp) showed that CD34 was highly expressed in the brain and testis, and moderately in the thymus, spleen, and bone marrow, but not in adult liver. However, day 12 to 14 fetal liver cells showed significant expression of CD34. Quantitative reverse transcription polymerase chain reaction showed that spleen, thymus, bone marrow, and testis RNA gave two bands of almost equal intensity, but in the brain a novel clone was expressed three times more than the other clone. Furthermore, Northern blot analysis using a probe (156 bp) specific for the spliced intracellular region confirmed the significant mRNA expression of a novel clone. Although the biologic significance of alternative splicing remains to be elucidated, it is suggested that a different carboxyterminal tail causes a change in signal transduction.

Two types of murine CD34 mRNA generated by alternative splicing

To characterize and clarify the function of CD34 antigen experimentally, we isolated two types of CD34 mRNA from a cDNA library of murine stromal cell line, PA-6 stimulated with lipopolysaccharide (LPS) and 12-o-tetra-decanoylphorbol 13-acetate (TPA) using a human CD34 probe. In addition to the clone (open reading frame [ORF]:1149bp) reported by Brown et al, a novel clone (ORF:978 bp) was obtained. The difference between the two clones was in the cytoplasmic portion of CD34; the former has 73 amino acids, while the latter has 16. We investigated the genomic sequence of cytoplasmic portion and found conserved nucleotide sequences at the exon-intron junction (GT ... AG). Thus, it was concluded that alternative splicing gave two types of CD34 mRNA. A novel clone contains the longer cDNA, including a insert of 156 bp, but results in a shorter predicted coding sequence because of the introduction of an inframe stop codon. Northern blot analysis using a murine cDNA probe (HindIII fragment, 900 bp) showed that CD34 was highly expressed in the brain and testis, and moderately in the thymus, spleen, and bone marrow, but not in adult liver. However, day 12 to 14 fetal liver cells showed significant expression of CD34. Quantitative reverse transcription polymerase chain reaction showed that spleen, thymus, bone marrow, and testis RNA gave two bands of almost equal intensity, but in the brain a novel clone was expressed three times more than the other clone. Furthermore, Northern blot analysis using a probe (156 bp) specific for the spliced intracellular region confirmed the significant mRNA expression of a novel clone. Although the biologic significance of alternative splicing remains to be elucidated, it is suggested that a different carboxyterminal tail causes a change in signal transduction.

Changes in chromatin and nucleic acids in rat tissues after two-week spaceflight

The quantitative changes in nucleic acids and chromatin breakdown were followed in blood, thymus and spleen in rats after 14 day flights on board the biosatellites Cosmos-1887 and Cosmos-2044. Quantitative nucleic acid changes within 8–11 h after landing were only mild, most statistically non-significant. An analysis at 48 h after landing showed a marked decrease in a total content of DNA and RNA in spleen and thymus. Within 8–11 h after landing, the symptoms of chromatin breakdown were found as is seen in an increased concentration of its fragments—polydeoxyribonucleotides. The obtained results show that a partial adaptation to microgravity occurs up to flight day 14 in lymphoid organs. Adaptation is accompanied with a reappearing of the sensitive cells. Their chromatin breaks down, then, in a final phase of flight due to hypergravity stress manifesting itself by a temporary increase in poly-deoxyribonucleotide concentration several hours after landing. The results are discussed in relation to the changes in chosen parameters after shorter or more prolonged flights.

Two distinct immunoglobulin heavy chain isotypes in a primitive, cartilaginous fish,Raja erinacea

Immunoglobulin heavy chain genes in Raja erinacea (little skate) are organized in clusters consisting of VH, DH, JH segments and CH exons (1). An immunoglobulin heavy chain mu-like isotype that exhibits 61-91% nucleotide sequence identity in coding segments to the Heterodontus francisci (horned shark) mu-type immunoglobulin is described. The overall length of the mu-type clusters is approximately 16 kb; transmembrane exons (TM1 and TM2) are located 3 to CH exon 4 (CH4). In three of four TM-containing genomic clones, a significant deletion is present in TM1. A second isotype of Raja immunoglobulin heavy chain genes has been detected by screening a spleen cDNA library with homologous Raja VH- and CH1-specific probes complementing the respective regions of the mu-like isotype. Weak hybridization with VH-specific probes and no discernable hybridization with C mu-specific probes were considered presumptive evidence for a second immunoglobulin isotype that nominally is designated as X-type. The Vx region of the X-type cDNA is approximately 60% identical at the nucleotide (nt) level to other Raja VH segments and thus represents a second VH family. Putative Dx and Jx sequences also have been identified. The constant region of the X-type immunoglobulin heavy chain gene consists of two characteristic immunoglobulin domains and a cysteine-rich carboxy terminal segment that are only partially homologous with the mu-like isotype. Genomic Southern blotting indicates that the V and C segments of both immunoglobulin heavy chain isotypes are encoded by complex multigene families. Vx- and different Cx-specific probes hybridize to different length transcripts in northern blot analyses of Raja spleen RNA suggesting that the regulation of expression of the X-type genes may involve differential RNA processing.

Persistent infection of mice by lactate dehydrogenase-elevating virus: transient virus replication in macrophages of the spleen

In order to assess whether the spleen is the major site of replication of lactate dehydrogenase-elevating virus (LDV) in mice during the acute phase of infection, LDV replication in the spleen was measured by electron microscopy and fluorescent antibody staining of tissue sections and northern hybridization of total spleen RNA with an LDV-specific cDNA probe, and the effect of splenectomy on LDV replication was determined. LDV RNA and antigens and infected cells, presumably macrophages, were present in the spleen in high concentrations 18–25 h post infection, but then rapidly disappeared to undetectable levels during the next 1–2 days. Thus, LDV clearly replicates in the spleen during the initial phase of infection, but LDV replication in the spleen is transient due to the cytocidal nature of LDV replication and destruction of all permissive macrophages in the spleen. Furthermore, spleen macrophages do not seem to represent the major source of LDV released into the circulation, since LDV viremia as well as anti-LDV antibody production were the same in splenectomized and control animals for at least 28 days postinfection.

Kinetic analysis of Ly‐6 gene induction in a T lymphoma by interferons and interleukin 1, and demonstration of Ly‐6 inducibility in diverse cell types

The Ly-6 locus contains multiple genes encoding cell surface proteins, two of which, when cross-linked by antibodies, effect antigen-independent activation of T lymphocytes. In this study, cDNA for Ly-6-encoded antigens have been used as probes to examine RNA from various tissues and transformed cell lines for constitutive levels of Ly-6 RNA expression. Analyses of RNA prepared from several different tissues revealed a high level of expression of Ly-6 RNA in kidney, spleen, heart and thymus, with a more moderate level of expression in liver, brain and lung tissue cells. A survey of various cell lines demonstrated the presence of Ly-6 RNA in many, but not all T lymphocytic cell lines, in L cells, the Meth A fibrosarcoma, in the TCMK kidney cell line, and in the Neuro-2a neuroblastoma. We also evaluated the expression of Ly-6 RNA in cells after treatments with interferons (IFN) and interleukin 1 (IL1). Treatment of lymphoid cells with IFN (alpha/beta and gamma), known to increase cell surface Ly-6 antigen expression in normal T cells, was correlated with increases in Ly-6 RNA levels. Increases in levels of RNA correlated with increases in levels of the Ly-6A/E or Ly-6C antigens. Several T lymphoid cell lines exhibiting Ly-6 RNA inducibility by IFN were similarly inducible with IL1. Kinetic experiments using one such line, (YAC-1), showed that the induction of Ly-6 RNA mediated by IFN-alpha/beta occurred rapidly (within 4 h), while the induction by IL1 required relatively more time (approximately 8 h). Although the actions of IFN-alpha/beta were not blocked by cycloheximide, the presence of this protein synthesis inhibitor significantly attenuated the effects of IL1 and IFN-gamma on Ly-6 RNA transcription. Induction by IFN-gamma as well as IL1 could be blocked completely by co-culture with anti-IFN-gamma, implicating IFN-gamma as a mediator of the induction by IL1.

Indiscriminate representation of VH-gene families in the murine B lymphocyte responses to Trypanosoma cruzi.

The utilization of the nine major homology families of VH-genes was quantitated in the B lymphocyte response to Trypanosoma cruzi infection of C57BL/6 mice. Normal and infected mice at various times after parasite inoculation were compared for VH-gene distribution of CFU-B produced by activated blasts recovered from spleen and lymph nodes, and for relative hybridization of total spleen RNA with each of the family probes. T. cruzi infection results in large increases of splenic RNA in the various homology families, and the numbers of activated CFU-B, reflecting the massive B lymphocyte responses. In acute phase, all nine families are expressed in roughly the same proportions as in normal mice, whereas in chronic infection, B cells expressing S107 and 7183 VH-genes might be preferentially stimulated. These results establish the polyclonal nature of the host response to T. cruzi infection.

Complete structure and organization of immunoglobulin heavy chain constant region genes in a phylogenetically primitive vertebrate.

Immunoglobulin (Ig) gene organization in Heterodontus francisci (horned shark), a phylogenetically primitive vertebrate, is unique. Homologous Ig heavy chain variable (VH) and constant region (CH) specific probes were used to screen a spleen cDNA library constructed in lambda gt11. Both secretory (SEC) and transmembrane (TM) cDNA clones were recovered; the latter were identified by a negative selection strategy. The complete sequence of the CH portion of a Heterodontus genomic DNA-lambda clone also was determined. The sequences of the individual CH genes differ from each other in all exons. When compared to mammalian prototypes, similarities in exon and intron organization as well as conservation of sequences involved with differential splicing of SEC and TM mRNA indicate that Heterodontus heavy chain genes are of the mu type, although intron lengths are uniformly longer in Heterodontus. Heterodontus genes are not associated, however, with the family of DNA sequences that have been implicated in heavy chain class switching in mammals. Spleen cDNA library screening and RNA blot analyses indicate that mRNAs encoding TM Ig are exceedingly rare. The relationship between this quantitative difference and the distribution of polyadenylation signal sequences suggests that regulation of Ig gene expression in Heterodontus may be highly dependent on position effects.

Cloning and Nucleotide Sequence of a Mouse Erythrocyte β-Spectrin cDNA

AbstractA rabbit monospecific antibody for mouse β-spectrin was used to screen a mouse anemic spleen cDNA expression library. A mouse β-spectrin cDNA clone was isolated and identified by its ability to make mouse β-spectrin-like antigens in Escherichia coli. This clone was used to probe total RNA from various mouse tissues. Anemic spleen RNA showed two strongly hybridizing RNA species of approximately 6 and 8 kb. Two very faintly hybridizing bands of about 6 kb and 10 kb could also be seen in total mouse brain RNA. All of these bands could be detected after hybridization under both stringent and nonstringent conditions. This suggests that erythroid β-spectrin may also be expressed in the brain. No bands could be detected in kidney, liver, or spleen RNA. Southern blot analysis of mouse genomic DNA showed a single hybridizing band after digestion with several restriction endonucleases even under nonstringent conditions. Nucleotide sequencing of the cDNA insert revealed almost complete identity between the N-terminus of the deduced amino acid sequence of the cDNA clone and the C-terminal 15 amino acids of a peptide derived from the β -8 repeat unit of human erythrocyte β-spectrin. The deduced amino acid sequence contained most of the conserved amino acids characteristic of the 106 amino acid repeat unit first found in human α-spectrin and thus provides the first evidence for a complete 106 amino acid repeat unit structure in β-spectrin.