Regulation of the immune response to tumor antigen. VIII. The effects of host specific anti-I-J antibodies on the immune response to tumors of different origin

The efficiency of in vivo therapy using alloantisera produced to interact specifically with I-J subregion encoded determinants has been investigated in two etiologically distinct syngeneic tumor systems, both of which have been shown to evoke suppressor T-cell host responses. Administration of 2 μl/day of anti-I-J^k alloantisera caused a significant reduction in the growth of the P815 methylcholanthrene (MCA)-induced mastocytoma or the 1316 ultraviolet (uv) radiation-induced fibrosarcoma in the syngeneic host. Inhibition of tumor growth with anti-I-J antibody treatment occurred in normal as well as in subcarcinogenically uv-treated hosts given the uv-induced 1316 fibrosarcoma, even though the normal host is capable of spontaneously rejecting the tumor graft in the absence of external manipulation. Evidence is also provided that the effects of anti-I-J antibody treatment are not due to direct interactions with the tumor cells, or to contaminating antiviral antibody activity within the antiserum. We have previously demonstrated the reduction of tumor growth in two antigenically distinct MCA-induced tumor systems (S1509a, SAI) using similar treatments. The data presented herein thus reinforce the possibility that such means of therapy may be beneficial to the treatment of a wide variety to tumor types where suppression represents a detrimental component of the host response, and may also provide some insight into the mechanisms underlying the effects of uv radiation on the immune response to tumor antigen.     

Inhibition of palatal epithelial cell death by altered protein synthesis.

Programmed cell death occurs in a defined region of the secondary palatal epithelium (medial edge) during its development in vivo or in vitro. The purpose of this study was to examine the effects of various inhibitors of macromolecular synthesis, particularly glycoprotein synthesis, on the death of palatal medial-edge epithelial cells in vitro. Rat palatal shelves explanted on gestational Day 15 and cultured singly showed medial-edge cell degeneration after 48 hr, whereas in the presence of 6-diazo-5-oxo-l-norleucine (DON), 2-deoxyglucose (DOG), or cycloheximide, cell death was prevented. This was in contrast to the lack of inhibition of cell death in the presence of actionomycin D or cytosine arabinoside. Selectively adding metabolites which bypass the effect of DON on various synthetic pathways demonstrated that the inhibition of cell death by DON was most likely due to a block in glucosamine formation. The synthesis and activity of various lysosomal enzymes were not affected by DON, whereas a marked decrease was observed with both cycloheximide and DOG. These results suggest that palatal epithelial cell death is not a passive event, but an active process requiring the programmed synthesis of specific proteins.     

Regulation of the immune response to tumor antigens. II. The nature of immunosuppressor cells in tumor-bearing hosts.

Immunosuppressor (IS) cells were found to be generated in tumor-bearing animals (TBA) within 24 hr after inoculation of tumor cells of the methylcholanthrene-induced Sarcoma 1509a and appeared to persist in the hosts as long as the tumor was progressing. However, IS cells disappeared with 5 days after extirpation of the tumor. Increasing doses of thymus cells of TBA increased the degree of suppression of tumor rejection in immune syngeneic animals. Ten million thymus cells of TBA were capable of suppressing significantly the tumor rejection. The IS cells were detected in the thymus, spleens, and draining lymph nodes, as well as in bone marrow of TBA, but could not be detected in the peripheral circulating blood. Since immunosuppressive activity of bone marrow cells from TBA was entirely abolished by the in vitro treatment of the cells with anti-theta serum and complement, the observed immunosuppression appears to be mediated by the T cell population.     

Role of methionine in the regulation of serine hydroxymethyltransferase in Eschericia coli.

Significant derepression of serine hydroxymethyltransferase is observed when metE or metF mutants of Escherichia coli K-12 are grown on D-methionine sulfoxide instead of L-methionine. The derepression is not prevented by addition of glycine, adenosine, guanosine, guanosine, and thymidine to the growth medium of methionine-limited metF cells showing that the effect is not due to a secondary deficiency of these nutrients. On the other hand, methionine-limited growth of a metA mutant leads to derepression of met regulon enzymes, but only a marginal increase in serine hydroxymethyltransferase activity. A prototrophic metJ strain grown on minimal medium has about the same serine hydroxymethyltransferase as the wild type. The enzyme activity of the metJ strain is not influenced by methionine, but it is partially repressed by glycine, adenosine, and thymidine. metK strains have about twice as much serine hydroxymethyltransferase activity as wild-type cells when grown on minimal medium; but when both types of cells are grown on medium supplemented with glycine, adenosine, guanosine, and thymidine, their enzyme activities are about the same. The results show that methionine limitation can lead to depression of serine hydroxymethyltransferase, but that the regulatory system is different from the one which controls the methionine regulon.     

Formation of internucleotide 3''-5'' phosphoramidate links by direct coupling of phosphoryl and amino groups.

The stepwise synthesis of oligomers derived from 5'-amino-5'-deoxythymidine 3'-phosphate and 5'-amino-5'-deoxy-3'-O-mono-p-methoxytrityl-thymidine is described. The internucleotide phosphoramidate links were formed by condensation of nucleoside 3'-phosphates with aminonucleosides by means of triphenylphosphine and dipridyl disulfide.     

Epidermal growth factor potentiates the induction of ornithine decarboxylase activity by prostaglandins in embryonic palate mesenchymal cells: effects on cell proliferation and glycosaminoglycan synthesis

Epidermal growth factor (EGF) and prostaglandins (PGs) have been implicated in the regulation of a number of developmental processes in the mammalian embryonic palate. Normal palatal ontogenesis is dependent on the presence and quite possibly on the interaction of various hormones and growth factors. The interaction between EGF and PGs in regulation of murine embryonic palate mesenchymal (MEPM) cell growth and differentiation was therefore investigated by monitoring the activity of ornithine decarboxylase (ODC), the principle and rate limiting enzyme of polyamine biosynthesis. ODC activity is tightly coupled to the proliferative and differentiative state of eukaryotic cells and therefore serves as a reliable indicator of such cellular functions. Treatment of confluent cultures of MEPM cells with EGF (1-50 ng/ml) resulted in a dose-related increase in ODC activity, while similar treatment with either PGE2 or PGF2 alpha (at concentrations up to 1 microM) did not elicit a dose-dependent increase in enzyme activity. Concurrent treatment of MEPM cells with EGF (20 ng/ml) and either PGE2 or PGF2 alpha (0.1-10000 nM) resulted in a marked prostaglandin dose-dependent induction of ODC activity, suggesting a strong cooperative interaction between these factors. ODC activity was maximal by 4 to 8 hr and could be completely inhibited by preincubation of the cells with actinomycin D or cycloheximide, indicating that de novo synthesis of RNA and protein is necessary for enzyme induction. Stimulation of ODC activity by EGF and PGE2 in these cells was not positively correlated with the level of cellular DNA synthesis but did result in a ninefold increase in the synthesis of extracellular glycosaminoglycans (GAGs), a key macromolecular family implicated in palatal morphogenesis. Stimulation of GAG synthesis was significantly inhibited by the administration of 5 mM DFMO (an irreversible inhibitor of ODC), indicating that the marked increase in GAG production was dependent, in part, on the induction of ODC activity by EGF and PGE2. Qualitative analysis of the palatal GAGs indicated that synthesis of several major classes of GAGs was stimulated. Collectively these data demonstrate a cooperative interaction between EGF and PGs in the induction of ODC activity. Such activity may serve to regulate the synthesis of GAGs, which are instrumental in mammalian palatal ontogenesis.