Natural suppressor (NS) cells found in the spleen of neonatal mice and adult mice given total lymphoid irradiation (TLI) express the null surface phenotype

We studied the surface markers of suppressor cells of the mixed leukocyte reaction (MLR) that are transiently present in the spleens of neonatal mice after birth and of adult mice after total lymphoid irradiation (TLI). Approximately 80% of the mononuclear cells in the spleen, within the first few days after birth or after TLI, express neither the Thy-1 antigen nor surface immunoglobulin (Ig). After 30 days, less than 20% of mononuclear cells bear this null phenotype. With the use of the panning technique, we showed that the suppressors of the MLR are confined to the null cell population. The null suppressor cells are not macrophages because they did not carry macrophage markers identified by the monoclonal antibodies anti-MAC-1 and F4/80. In addition, the suppressor cells did not stain for nonspecific esterase and did not adhere firmly to plastic or glass. Spleen cells from TLI-treated mice maintained their suppressive capacity after culture in vitro for 6 to 8 wk. The cultured suppressor cells did not develop mature T cell, B cell, or macrophage markers during this time interval. Thus, the suppressor cells did not appear to be precursors of the latter cells. There was no clear relationship between the suppressor activity of the spleens and natural killer (NK) activity; the kinetics of these activities in newborn spleen appear to be inversely related. The suppressor cells, however, are similar to NK cells in that both are found in the absence of antigenic challenge, lack antigen specificity, and bear the null surface phenotype. Thus, we have termed the former cells natural suppressor (NS) cells.     

Monoclonal antibodies against diphtheria toxin fragment A : Characterization and introduction into living cells

Monoclonal antibodies against fragment A of diphtheria toxin were isolated and characterized. Three antibodies with similar affinities for fragment A had different effects on the NAD:EF2-ADP ribose transferase activity of fragment A; i.e., antibody DA1 almost completely inhibited the enzymic activity at a molar ratio of one, whereas DA2 inhibited only partially and DA3 had no effect. However, when fragment A176 from the mutant toxin CRM176 (about 1/10 as active as wild type) was used, DA2 proved a more effective inhibitor than DA1. The affinities of these antibodies for the enzymically inactive mutant fragments, A197 and A228, were significantly less manifest than for wild-type fragment A. Binding of the antibodies to whole toxin and the chain termination mutant CRM45 was weak. When DA2 was introduced into Vero cells growing in monolayers, by using the red cell ghost fusion method, the cells became resistant to CRM176. The anti-fragment A antibodies may serve as the basis of a simple method for selection of cells into which other molecules have been co-introduced.     

Assignment of a gene coding for a human T-cell antigen with a molecular weight of 40,000 daltons to chromosome 17

Hybrid human-mouse T-cell clones reactive with Tp40 antibody, which detects cluster of differentiation (CD)7 antigen on human T lymphocytes, were established. Karyotype analysis showed that human chromosome 17 was essential for the expression of CD7 antigen. The presence of this chromosome was confirmed by enzyme analysis of galactokinase, which is coded by a gene on human chromosome 17.     

Co-electroporation of rice protoplasts with RNAs of cucumber mosaic and tobacco mosaic viruses

Cucumber mosaic virus (CMV) RNA was used to study electroporation conditions suitable for protoplasts from rice suspension cultures. Rice protoplasts required a stronger and shorter electric pulse than tobacco protoplasts for introduction of viral RNA. Under optimized conditions, CMV infection was established in 65 % of electroporated protoplasts. In contrast, electroporation with tobacco mosaic virus (TMV) RNA did not result in infection of rice protoplasts. However, when TMV RNA was electroporated into rice protoplasts together with CMV RNA, TMV production was demonstrated in 15 % of protoplasts. Differential staining with fluorescent antibodies against the two viruses showed that the protoplasts producing TMV were without exception also infected by CMV. The results show that CMV replicates in rice protoplasts by itself, whereas TMV does so only with the aid of CMV.Abbreviations CMV cucumber mosaiv virus - PBS phosphate buffered saline - TMV tobacco mosaic virus.     

Abnormalities in DNA rearrangements of immunoglobulin gene loci in precursor B cells derived from X-linked agammaglobulinemia patient and a severe combined immunodeficiency patient

In an attempt to characterize the genes that cause immunodeficiencies such as X-linked agammaglobulinemia (XLA) and severe combined immunodeficiency (SCID) we established precursor B-cell lines by transforming the patients' bone marrow cells with Epstein-Barr viruses. DNA rearrangements of immunoglobulin J_H gene loci were observed on both chromosomes in pre-B cells derived from an XLA patient. We cloned and characterized both rearranged bands from one cell line. Both of the rearrangements occurred between D _H and J _H gene loci without the V_H DH structure. On the other hand, JH gene loci retained the germline configuration on both chromosomes in almost all the transformants derived from a SCID patient that had been determined according to their surface markers, to be in an early precursor B-cell stage. The implications of the observations are discussed.     

New type of pullulanase from Bacillus stearothermophilus and molecular cloning and expression of the gene in Bacillus subtilis.

A new type of pullulanase which mainly produced panose from pullulan was found in Bacillus stearothermophilus and purified. The enzyme can hydrolyze pullulan efficiently and only hydrolyzes a small amount of starch. When pullulan was used as a substrate, the main product was panose and small amounts of glucose and maltose were simultaneously produced. By using pTB522 as a vector plasmid, the enzyme gene was cloned and expressed in Bacillus subtilis. Since the enzyme from the recombinant plasmid carrier could convert pullulan into not only panose but also glucose and maltose, we concluded that these reactions were due to the single enzyme. The new pullulanase, with a molecular weight of 62,000, was fairly thermostable. The optimum temperature was 60 to 65 degrees C, and about 90% of the enzyme activity was retained even after treatment at 60 degrees C for 60 min. The optimum pH for the enzyme was 6.0.     

Monoclonal antibodies to poly(adenosine diphosphate ribose) recognize different structures

Two hybridomas producing monoclonal antibodies to poly(adenosine diphosphate ribose) [poly(ADP-Rib)] were established. One antibody, 10H (IgG3, kappa), bound to most of the poly(ADP-Rib) preparation, which consisted of molecules of various sizes of more than 20 ADP-Rib residues. The binding of this antibody was inhibited by not only poly-(ADP-Rib) but also a monomer unit of poly(ADP-Rib), Ado(P)-Rib-P. The sites protected by antibody 10H were isolated and analyzed by hydrolysis with alkaline phosphomonoesterase and then snake venom phosphodiesterase. The sites contained the same amounts of monomer units and branched portions [Ado(P)-Rib(P)-Rib-P] as the original poly(ADP-Rib) molecules but a lower average number of branched portions per molecule than in the original molecules. The other antibody, 16B (IgM, lambda), reacted with only 50% of the radioactive poly(ADP-Rib), and its binding was not inhibited by a monomer unit. This antibody protected 25% of all the poly(ADP-Rib) molecules from hydrolysis by snake venom phosphodiesterase. The protected sites contained twice as many branched portions per molecule as the original poly(ADP-Rib) molecules. These results show that the two monoclonal antibodies recognize different structures of poly-(ADP-Rib); 10H antibody recognizes the linear structure with ribose-ribose linkages, and 16B antibody may recognize specific structures, including the branched portions of poly-(ADP-Rib).     

Effect of chromium(III) on nucleolar RNA synthesis

The enhancement of hepatic nucleolar RNA synthesis induced by Cr(III) in partially hepatectomized rats and its mechanisms are described. Cr(III)-administered (0.5 mg Cr/kg, ip) and then partially hepatectomized rats were significantly enhanced in the hepatic nucleolar RNA synthesis at the very early stage of liver regeneration. This enhancement was caused both by the induction of newly found nucleolar Cr-bound protein of 70 kD (Cr-p70) and by the activation of nucleolar chromatin, both of which arose from nuclear accumulation of Cr together with partial hepatectomy. Studies on the mechanism of this enhancement indicated that the Cr-p70 bound to the activated nucleolar chromatin and loosened its higher-order structure, resulting in an increase of the B-form fraction of chromatin DNA. The degree of this loosening well correlated with the amount of Cr-p70 bound to chromatin and also with the extent of elevation of RNA synthesis. Some molecular species of nonhistone proteins in chromatin were found to play an important role in the interaction to Cr-p70. These results suggest a possibility that the action of Cr is involved in cell proliferation process.