Regulation of the secondary antibody response in vitro. Enhancement by actinomycin D and inhibition by a macromolecular product of stimulated lymph node cultures

Depression of cell-mediated immunity following inoculation of Trichinella spiralis extract in the mouse

Mice pretreated with Trichinella spiralis extract (TsE), or infected with the parasite, rejected primary skin allografts in 18-23 days and secondary allografts in 12-16 days. Mice pretreated with saline or with bovine serum albumin (BSA) rejected the primary allografts in 12-18 days and did not accept the secondary grafts. Inoculation of increasing doses of parental spleen cells from mice pretreated with saline or with BSA in F1 hybrids produced proportionately stronger graft-versus-host reactions (GvHR) whereas increasing doses of cells from TsE pretreated mice reduced proportionately the capacity of the inoculum to induce a GvHR. Immunodepression of the parental cells was obtained with 7 and with 4, but not with 2, daily injections of TsE. The depression waned rapidly after the treatment with TsE but a significant degree still remained after 3 days. Immunodepression by TsE cannot be solely explained by antigenic competition and although our results are consistent with the induction of suppressor cells, it is probable that other mechanisms are also involved.

Partial characterization of a T cell-derived factor that suppresses the initiation of the humoral immune response in vitro

Specific anamnestic stimulation of spleen cells from mice immunized 7 days earlier with horse erythrocytes (HRBC) generated the release of a soluble factor that was capable of suppressing the initiation of the in vitro primary gammaM immune response to sheep red blood cells (SRBC), as well as to the immunogen that elicited its formation. Moreover, the suppressive macromolecule (mol. wt yields to 34,000), derived from antigen-activated, HRBC-primed T lymphocytes (but not B cells), inhibited the secondary gammaM and gammaG anti-SRBC plaque-forming cell responses of SRBC-primed spleen cells. The active material was resistant to treatment with DNase and RNase, but was inactivated by protease (10 microgram/ml, 30 min) or exposure to mild heat (56 degrees, 30 min). The antibody initiation suppressor factor (AISF) was concentrated and partially purified by gel filtration, followed by poly-acrylamide gel electrophoresis.

Non-specific suppression of the initiation of the immune response to a heterologous immunogen by supernatants from specifically stimulated, primed lymphoid cells

In cultures of spleen cells from mice immunized with horse erythrocytes (HRBC) 7 days earlier, the simultaneous addition of sheep erythrocytes (SRBC) and the priming antigen on day 0 resulted in the suppression of the anti-SRBC plaque-forming cell (PFC) response by day 5 compared to the response of similar cultures that received only SRBC. The cell-free culture fluid from specifically-stimulated, HRBC-primed cells, but not normal cells, contained a factor that nonspecifically inhibited the anti-SRBC PFC response of cultures of normal spleen cells to which SRBC and diluted supernatant aliquots were added at the beginning of culture. Suppressor activity was not manifest unless active supernatants were added on day 0 of a 5-day culture period. Inhibition of the reference plaque response was not due to cytotoxicity of the active material, decreased immunogenicity of the SRBC, or switchover from IgM to IgG plaque formation. The soluble mediator was released slowly into the culture fluid, with linear kinetics, from specifically activated, primed cells, with maximum suppression obtained with the 120-h supernatant. When active supernatants were fractionated by gel filtration over Sephadex G-150, the inhibitory factor eluted with molecules of about 34,000 mol. wt.

Effect of distamycin A on the primary and secondary immune response of mouse spleen cells in vitro against sheep erythrocytes

The effect of distamycin A (DMC) on the primary and secondary immune response of mouse spleen cells, cultured in vitro in the presence of sheep erythrocytes as an antigen, was studied. It was found that the primary response was extremely sensitive to DMC during the first 24 hrs of culture and then gradually became more and more resistant to the immunosuppressive effect of the drug. Right from the start of culture, however, the secondary response was much more resistant than the primary one to the inhibitory action of DMC. These results could not be reproduced by treating the cultures with inhibitors of DNA-dependent DNA synthesis (such as cytosine arabinoside) or inhibitors of DNA-DEPENDENT RNA synthesis (such as actinomycin D).

Regulation of the secondary antibody response in vitro. II. Chemical properties of an antibody inhibitory material (AIM) produced in antigen-stimulated rabbit lymph node organ culture

A material inhibiting antibody synthesis in vitro is produced during the productive phase by rabbit lymph node organ cultures undergoing a secondary response. This antibody inhibitory material (AIM) has been isolated from serum-free medium taken from the cultures and also extracted from lymph node fragments as late as their 4th wk in vitro. AIM inhibits most strikingly the early productive phase of the secondary response in vitro (i.e, during the 2nd wk). AIM isolated from cultures undergoing a given immune response inhibits the same as well as different responses, thus indicating an immunologically nonspecific effect. Ultrafiltration and related studies reveal that the molecular size of AIM is 10,000-50,000 daltons and that it is not antibody. AIM can readily be separated from 7S globulin by use of CM-cellulose. The inhibitory activity of AIM is lost by digestion with ribonuclease. Thus the avoidance of serum with its high levels of ribonucleases may be crucial in the study of this material. The presence in eukaryotic cells of metabolic regulators, governors, etc. has been postulated largely by analogy with microbial systems (27). There is little direct evidence about the chemical nature of these presumed regulators. Our data on the RNase sensitivity of AIM raises the possibility in this lymphoid system of regulation by a species of RNA.

Specific heterologous enhancement of immune responses. IV. Specific generation of a thymus-derived enhancing factor

In short-term cultures of thymocytes from tetanus toxoid-immunized mice, the addition of 1 ng of toxoid generated the release of a soluble factor which was capable of enhancing the immune response to a heterologous immunogen. The addition of supernatants from such cultures to assay cultures of sheep erythrocyte-stimulated normal spleen cells produced a significant augmentation of the hemolytic plaque response. Culture fluid from similar cultures of normal thymocytes or primed thymocytes cultured without the priming antigen were inactive. The enhancing factor was nondialyzable, heat stable (56 degrees C, 30 min), resistant to DNAse and RNAse, but was inactivated by protease. A factor produced by specifically stimulated primed spleen cells had similar characteristics. In toxoid-stimulated, mixed cell cultures containing primed thymocytes or spleen cells and normal spleen cells, tenfold fewer thymocytes than spleen cells were needed to produce a comparable degree of enhancement of the anti-sheep erythrocyte plaque-forming cell response.

Kinetics of antibody production by single cells. II. The action of transcription and translation inhibitors upon the metabolism of haemolysin-secreting cells

The plaque-forming cell (PFC) population from spleens of mice at the peak of the primary immune response against sheep red blood cells has been analysed using a plaque-assay technique and automatic photographic equipment which recorded plaque formation and growth within a carboxymethyl-cellulose gel. Preliminary biochemical studies, using tritiated uridine and leucine as markers, and actinomycin D and puromycin as inhibitors of transcription and translation respectively, were performed with normal spleen cells. The effect of each of these inhibitors was then tested by means of the plaque-assay technique.

The formation and subsequent growth of a plaque within a normal gel are processes in which both transcription and translation are required for haemolysin secretion. It was found that in PFC populations, the functional lifespan of messenger RNA (m-RNA) specific for haemolysin translation has a mean value of 4 hours, while the functional lifespan of total RNA in whole spleen cell populations is not more than 2 hours. The pool of haemolysin stored in a PFC has a mean secretion time of 1.5 hours.

There was considerable heterogeneity with regard to the storage of haemolysin and to the functional lifespan of the haemolysin-specific m-RNA from one PFC to another within the spleen population. Furthermore, some PFC which displayed a high secretion rate of haemolysin were unaffected by actinomycin D, while others were inhibited within a few hours. The short-term action of each inhibitor has been studied. Puromycin was found to have a reversible action on PFC expression, while a 1-hour duration of action of actinomycin D was sufficient to inhibit irreversibly the subsequent PFC expression.

A kinetic and quantitative analysis of antibody and protein synthesis during the primary response to keyhole limpet haemocyanin

Rabbits were injected with alum-precipitated keyhole limpet haemocyanin. On various days after immunization popliteal lymph node cells were prepared for synthesis of antibody as well as non-antibody proteins by incorporation of ¹⁴C-amino acids. Antibody and proteins were characterized by gel filtration, radio-immunoelectrophoretic and zone electrophoretic analyses of the culture media. Some `natural' antibody appeared to be synthesized by lymph node cells from uninjected animals. The first definite increase in numbers of nucleated lymph node cells and in antibody synthesis occurred on the third day after immunization. The peak of cell numbers and antibody synthesis was attained on the sixth day after antigenic stimulation. The antigen-stimulated cells also synthesized increased amounts of non-antibody proteins, including IgM and IgG, and proteins tentatively identified as α₂ macroglobulin, α₁ globulin and a microglobulin. Most of the radioactive protein which was synthesized following injection of antigen was demonstrably not antibody. Both IgM and IgG antibody were synthesized at all times, but relatively more radioactivity was incorporated into IgM antibody on day 3 and into IgG antibody on day 6 after immunization.

Specificity of deoxyribonucleic Acid intercalating compounds in the control of phenylalanine ammonia lyase and pisatin levels

Compounds with planar triple ring systems such as acridine orange, 9-amino acridine, 9-amino-1,2,3,4-tetrahydroacridine (tacrine), 6,9-diamino-2-ethoxyacridine lactate monohydrate (DE-acridine), 6-chloro-9-(3'-diethylamino-2'-hydroxypropylamino) -2-methoxyacridine.2 HCl (CDM-acridine), quinacrine, 6-chloro-9-(4'-diethylamino-1'-methylbutylamino) -2-methoxy-1,10-diazaanthracene (CDM 1,10-diazaanthracene), thionine, azure A, methylene blue, and pyronine Y when applied to excised pea pods were potent inducers of phenylalanine ammonia lyase or of pisatin, or of both. Compounds with an array of structural variation around the planar three-ring system were tested for their ability to induce these responses in pea tissue. In general, dimethylamino, diethylamino, or amino substitutions at position 2 and 6 or an amino (with or without an aliphatic side chain) substitution at position 9 of the three-ring system augmented induction potential. Methyl green, methylene blue, 2,7-diaminofluorene, nile blue, neutral red, pyrogallol red, ethidium bromide, nogalamycin, quinine, chloroquine, spermine, 8-azaguanine, gliotoxin, chromomycin A(3), actinomycin D, and mitomycin C were also potent inducers. The inhibition of phenylalanine ammonia lyase induction by the application of actinomycin D (300 micrograms per milliliter) or 6-methylpurine (1 milligram per milliliter) within 1 hour after inducer application indicated that newly synthesized RNA is necessary for induction. Phenylalanine ammonia lyase induction was also inhibited by cycloheximide (150 micrograms per milliliter).

Effect of actinomycin D, cycloheximide, and acute blood loss of ferritin synthesis in rat liver

1. The mechanism of the stimulation of ferritin synthesis by iron in vivo has been studied in rat liver. Ferritin synthesis and turnover was measured by [(14)C]leucine incorporation. 2. Actinomycin D had no inhibitory effect, after administration of iron, on [(14)C]leucine incorporation into ferritin but appeared to augment the effect of iron on ferritin synthesis. 3. Cycloheximide completely abolished the stimulation by iron of [(14)C]leucine into ferritin and was subsequently utilized to show that iron acts in vivo by translational induction of apoferritin synthesis, rather than by stabilization of apoferritin or its precursors. 4. This conclusion was confirmed by showing that 2 days after acute bleeding, when iron was in the process of being removed from hepatic ferritin stores, ferritin synthesis was decreased whereas breakdown rates were unchanged.