Enhancement of antibody production and protection against systemic anaphylaxis by large doses of vitamin C.

Male and female guinea pigs receiving, respectively, 100 and 280 mg/day Vitamin C throughout the duration of immunization showed enhanced humoral antibody production to bovine serum albumin (BSA) and, in castrated females, to penicilloyl-coupled guinea pig gamma-globulin. A significant degree of protection was afforded against fatal anaphylactic shock in passively sensitized males. Under appropriate conditions of sensitization with rabbit anti-HGG and challenge with human gamma-globulin, 8 of 20 unsupplemented animals died of shock, whereas in the group receiving 280 mg Na ascorbate/day for 4 days preceding passive transfer and again 60' before challenge, only 2 of 18 died. The rate of dose-dependent mortality observed when groups of passively sensitized animals were challenged with increasing doses of antigen was reduced in animals supplemented as above. Actively immunized guinea pigs were not protected by 5 daily doses of 280 mg Na ascorbate given prior to challenge. There were no significant differences in the total hemolytic activity of the serum nor in the C3 and C4 components of complement in immunized animals. There was no change in the concentration of Cl esterase in non-immunized controls, but immunization with BSA was followed by a rapid decline in Cl concentration, the decrease being greater in the ascorbate-treated group than in the unsupplemented controls, possibly reflecting a higher level of circulating immune complexes in the former case.

The effect of variations in vitamin C intake on the cellular immune response of guinea pigs.

The uptake of tritiated thymidine by isolated peripheral blood lymphocytes obtained from male guinea pigs immunized with bovine serum albumin was studied in animals maintained on various amounts of Vitamin C for 28 days. Animals were pair-fed on ascorbate-free diet and were supplemented intraperitoneally with 0, 25, or 250 mg Na-ascorbate per day. Scorbutic animals lost weight rapidly during the final 2 experimental weeks. Their daily food intake averaged only 4 g/day during the last week; thus, pair-fed ascorbate-supplemented groups were also subjected to acute nutritional stress. Lymphocytes from guinea pigs receiving 250 mg Na-ascorbate per day incorporated in vitro the highest amounts of tritiated thymidine both in the absence of nonspecific mitogen and in the presence of concanavalin A or phytohemagglutinin. Responses to lipopolysaccharide were not conclusive. Total circulating white cells counts and relative numbers of T and B lymphocytes were assessed in a second study made under identical constraints. In scorbutic animals the percentage of B lymphocytes increased and that of T lymphocytes decreased continuously over the 4-week period. The opposite effect was observed in vitamin C-supplemented animals. These studies suggest that very high doses of ascorbate support elevated mitotic activity after 4 weeks of much reduced food intake.

Sex hormones and the immune response. I. Host factors in the production of penicillin-specific antibodies in the female guinea pig.

Female guinea pigs between 500 and 650 g produced the highest precipitation titers to penicilloyl-coupled guinea pig gamma-globulin of an array of animals ranging in weight from 350 to 850 g. When one or two depot injections in complete Freund's adjuvant were succeeded by saline boosters, the response maximized within 1 week after the first booster (in phase with the maximum output of IgM); subsequent boosters rapidly reduced the titer. The observed response was directed primarily at the hapten, as no reaction was evident to heterologous carrier (KLH) until the anti-hapten titer had declined. The daily administration of estradiol for 23 days after the last antigen inoculation prevented the decay of titer, whereas the titer of the controls or progesterone-treated animals dropped by 40--50% during that interval.

Sex hormones and the immune response. II. Perturbation of antibody production by estradiol 17beta.

The administration of 75 microgram/kg of estradiol 17beta at successively later stages in the immune response of female guinea pigs to penicilloyl-coupled cavian globulins showed that this steroid reduces the rate of attainment of the maximum titer, the magnitude of the titer achieved, and the rate of titer decay. Control titers maximized at the third experimental week and diminished to one third the peak value by the 6th week. When steroid treatment was begun coincidentally with inoculation (week 0), the peak titer was delayed by 3 weeks, and by 2 weeks when hormone priming was begun at week 1 or 2. The highest antibody titers achieved in the presence of estrogen were 25-30% lower than those of sesame oil controls. The greatest immunosuppressive effect was observed when estradiol was given at the peak of the immune response, the titer dropping by 50% and remaining at that level for the next 4 weeks in spite of continued antigen inoculation and steroid treatment. Titer decay after the end of the inoculation course was prevented by estradiol but not by progesterone, CHP, or these same oil vehicle.

PIP: Estradiol profoundly affected production of humoral antibodies in guinea pigs by slowing the time course of the immune response during the inoculation phase and by reducing the rate at which the titer decayed after immunization was discontinued. These effects were achieved by administration of 75 mcg/kg of estradiol 17 beta at successively later stages in the immune response of female guinea pigs to penicilloyl-coupled cavian globulins. Control titers maximized at the 3rd experimental week and diminished to 1/3 the peak value by Week 6. Coincident inoculation and steroid treatment (Week 0) delayed the peak titer by 3 weeks, and it was delayed by 2 weeks when hormone priming was begun at Week 1 or 2. Titers of sesame oil controls were always higher than the highest antibody titer achieved in the presence of estrogen (25-30% lower with estrogen). The greatest immunosuppressive effect took place when estradiol was given at the peak of the immune response; the titer dropped by 50% and remained at that level for the next 4 weeks despite continued antigen inoculation and steroid treatment. Estradiol prevented titer decay after the end of the inoculation course, but progesterone, a progesterone analogue CHP, and seasame oil vehicles did not.

An analysis of the toxic actions of purified streptolysin O on the isolated heart and separate cardiac tissues of the guinea pig.

The response of isolated guinea pig hearts to perfusion with purified streptolysin O is characterized by a rapid, but transient, decrease in rate and amplitude of contraction; these reactions are superimposed upon a gradual, irreversible, loss of ventricular contractility. At ventricular standstill, the atria continue to beat spontaneously in a normal way. Isolated ventricle strips prepared from such preparations can be driven electrically, and their behavior is functionally indistinguishable from that of similar preparations made from normal hearts. Tests on spontaneously beating isolated atrial pairs show that the toxin induces a dose-dependent, reversible, decline in rate and amplitude which is accompanied by a marked, but transient, increase in the velocity of repolarization of the intracellular potential. The atrial reactions were completely blocked by atropine and potentiated by eserine. Acetylcholine was detected in the perfusates obtained by incubating a large pool of atrial tissue with active toxin, supporting the inference that the transient mechanical and electrophysiological reactions to toxin might be consequences of the release of acetylcholine from these tissues by the active toxin. Control studies showed that only the active toxin had the capacity to induce the cardiac responses. The toxin was active only in the reduced but not the oxidized form. The effects of the active toxin were modified if it were heated prior to challenge, and they could be neutralized by specific antiserum and inhibited by cholesterol. Since the driven ventricle strip was mechanically and electrophysiologically insensitive to streptolysin O, the irreversible changes in the whole heart must have occurred because of a defect in the atrioventricular conduction system.

Passive sensitization in vitro: effect of antibody concentration on the lag period and velocity.

Strips of guinea pig ileum were sensitized in vitro in various concen trations of rabbit antibody prepared against ovalbumin. The dependence of the first-order velocity constants upon antibody concentration was hyperbolic. The limiting velocity constant was 0.0097 per minute, and the antibody concentration giving half the limiting velocity was 0.0035 milligrams per milliliter. The lag period varied inversely with the logarithm of the antibody concentration.