STUDIES ON ANTIBODY PRODUCTION. XII. INHIBITION OF PRIMING BY DRUGS

STUDIES ON ANTIBODY PRODUCTION. 13. THE EFFECT OF CHLORAMPHENICOL ON PRIMING IN MICE

Young adult mice were primed with 20 Lf (56 µg) of diphtheria toxoid and given a second injection of the same size 40 days later. This procedure produces a reproducible secondary response which can be used as a standard. Chloramphenicol in maximum dosage prevents the unknown process by which the animal is primed for the second response. To be fully inhibitory, the drug must be given from the hour of the first antigen injection in maximum dosage for 2 weeks. A delay of 48 hours in starting the drug allows completion of the priming process, and shorter delays produce partial inhibition. Hence the initiation of priming is a rapid process sensitive to chloramphenicol. Subsequent changes in the cell population necessary for the full development of priming are not sensitive to chloramphenicol. The secondary antibody response is not inhibited in mice by chloramphenicol at the doses employed.

Activity of various immunosuppressive drugs on tuberculin hypersensitivity reaction in chickens

Drug induced immunosuppression of chicken immune response was studied in F1 hybrids of the CB and IC inbred lines. In tuberculin reaction complete inhibition of wattle swelling was induced by the administration of methotrexate, colcemid (1 mg/KBW), and 6-mercaptopurine. The cellular infiltration was substantially reduced in these cases. Cyclophosphamide and colcemid (0.1 mg/KBW) reduced partially the wattle swelling but had no apparent effect on the cellular infiltration. Acetinomycin D did not affect in measurable degree the wattle swelling. The histologic picture was in this case the same as in the control animals. The same drug administration schedule had less pronounced effect on anti-HSA antibody production. No anti-HSA antibody was found after the 500 mg/animal doses of 6-mercaptopurine. Significant reduction of anti-HSA titres was found after 50 mg/animal doses of 6-mercaptopurine, colcemid (1 mg/KBW), 25 MG/KBW or cyclophosphamide and after the methotrexate treatment.

On the mechanism of immunological tolerance in cyclophosphamide-treated mice

The mechanism of immunological tolerance of sheep red blood cells (SRBC) in mice treated with a single dose of cyclophosphamide was studied. Specific tolerance lasted for as long as nine months in some animals, and its maintenance required the repeated administration of SRBC. Anti-SRBC antibody-forming cells were significantly reduced in the tolerant mice, and X-irradiated recipients of their spleens were specifically tolerant of SRBC. The smallest number of SRBC required for the induction of tolerance was 10⁷; this was the smallest number of SRBC that could elicit antibody synthesis within 5 days in normal mice. Since the effects of cyclophosphamide on antibody-forming cells last only 5 days, it was concluded that the mechanism of tolerance induction involved destruction of antigen-stimulated cells. In support of this is the finding that mice treated with small doses of cyclophosphamide were rendered tolerant only when SRBC were given before the drug. Drug-induced immunological tolerance thus appears to differ significantly from both pneumococcal polysaccharide paralysis and classical, acquired tolerance. A central loss of immunocompetence does not occur in the former, while the latter requires for its induction the administration of antigen in a dose or form that does not stimulate antibody synthesis.

The effect of actinomycin-D on the haemopoietic and immune response to tetanus toxoid

A single dose of 15 μg (0·6 mg/kg) Actinomycin-D administered to female BDF₁ mice after intraperitoneal injections of pertussis vaccine and tetanus toxoid caused: (1) a prolonged depression in thymic and splenic weights; (2) an inhibition of the bone marrow leucocytosis which normally occurs between the 2nd and 14th days after antigen injection; (3) a blood leucopenia and marked decrease in the number of mononuclear cells in the inflammatory exudate during both the primary response and a secondary response initiated 4 weeks later; and (4) an inhibition of primary immunization, as evidenced by low antitoxin titres 4 weeks after priming, and by the failure to achieve a normal secondary response to a challenging injection of antigen given 4 weeks later.

It was suggested that the sensitivity of mononuclear cells to Actinomycin-D may be responsible for the suppression of priming, possibly by preventing RNA synthesis and differentiation induced by antigen.

Relationship of germinal centers in lymphoid tissue to immunological memory. II. The detection of primed cells and their proliferation upon cell transfer to lethally irradiated syngeneic mice

White-pulp cells and whole spleen from donor mice immunized with sheep erythrocytes were transferred intravenously to heavily irradiated mice. The numbers of plaque-forming cells and the amount of hemagglutinating antibody produced after reexposure to antigen were measured. When reexposure to sheep erythrocytes was delayed, a much greater response occurred in the transferred cells. Peak responsiveness was reached at 24 hr after transfer. This "lag effect" was greatly reduced by repeated injections of 5-bromodeoxyuridine into the recipient mice prior to challenge with antigen. It was therefore concluded that much of the increase in responsiveness was due to a proliferation of "primed" cells after cell transfer. The fact that a significant response was given by the transferred cells in spite of 5-bromodeoxyuridine treatment suggested that some of the primed cells were nondividing. White pulp was a much richer source of responsive cells than was whole spleen.

Differentiation and functional expression of potential antibody-producing cells in the presence of chloramphenicol

Rabbits were immunized with diphtheria toxoid combined with complete Freund's adjuvant. Half of the animals were started on intramuscular injections of chloramphenicol 24 hr before the injection of the antigens. There was a general depression of protein synthesis in the immune system in the presence of chloramphenicol, but a greater effect on the synthesis of antibody than on the synthesis of proteins necessary for reproduction and maturation. In contrast to the finding of antibody in cells of the spleen and in the circulation of the control animals, those animals receiving chloramphenicol did not have measurable circulating antibody, and their spleens contained only a few cells with intracytoplasmic antibody late in the course of the experiment. Cytologically there was maturation of potential antibody-producing cells in the red pulp and nonfollicular white pulp of the spleen while the animals were receiving chloramphenicol. These cells developed more slowly, and were fewer and smaller than those of the control animals. They had numerous small, electron-opaque particles in their cytoplasm early in development. Ribosomes were synthesized, though fewer in number. The endoplasmic reticulum formed more slowly.

Inhibition of the secondary antibody response in vitro by salicylate and gentisate

Salicylate inhibition of the secondary antibody response initiated in vitro on day 0 has been studied in cultures of rabbit lymph node fragments. Levels of 1.25 to 1.5 mM (0.20 to 0.24 mg/ml) sodium salicylate present in serum-free medium throughout an 18- or 21-day culture period completely inhibit the secondary response. This inhibition is largely accomplished by the drug's action during the first 9 days, which corresponds to the inductive phase for this culture system. Relatively little inhibition is produced by adding the drug only after day 9, although over 90% of the antibody produced during a 21-day experiment is synthesized after day 9. Studies with media of different pH's show that this inhibition is more correctly a function of the nonionized salicylic acid concentration in the medium than of the total salicylate concentration. Arguments are presented against the possibility that salicylate at the levels used here inhibits antibody synthesis by uncoupling oxidative phosphorylation. Acetylsalicylic acid (aspirin) produces the same degree of inhibition in vitro as do equimolar concentrations of sodium salicylate. Gentisate (5-hydroxysalicylate) is 15-fold more effective in producing 50% inhibition than salicylate; its temporal pattern of inhibition is similar to that of salicylate.

The immune response to heterologous red cells in mice

Several parameters such as dosage and schedule of antigen injection were examined. The effect of a single intraperitoneal or intravenous injection of various amounts of sheep red cells (SRBC) was studied over a dose range of more than 10⁵. Approximately 5×10⁷ SRBC was the optimal amount of antigen beyond which no further increase in titre occurred.

Multiple injections and overloading the organism with large amounts of SRBC did not result in a depression of the immune response.

Immunization with SRBC incorporated into incomplete Freund's adjuvant was slightly inferior to immunization with SRBC suspended in saline. The response depended on the antigen concentration in the adjuvant mixture rather than on the absolute amount of antigen injected.

Early in immunization antibodies against SRBC belong to the 19S class and change gradually into 7S antibodies. 19S and 7S haemolytic activity was mercaptoethanol-sensitive.

From absorption experiments it was concluded that the mouse antibody against SRBC has specificities other than anti-Forssman, anti-mononucleosis and anti-serum sickness and is directed against an isophilic heat-labile antigen(s).