Quantitative effects of nutritional essential amino acid deficiency upon immune responses to tumors in mice

Mice were fed diets deficient in a single essential amino acid, and the primary immune responses to inoculation of allogenic tumor cells was measured by in vitro assay of cellular immunity. Moderate reduction of the amino acids phenylalanine-tyrosine, valine, threonine, methionine-cystine, isoleucine, and tryptophane in the diet produced profound depression of hemagglutinating and blocking antibody responses, although cytotoxic cell-mediated immunity remained intact. These diets had previously been shown to result in a selective depression of tumor growth in mice. Limitation of the amino acids arginine, histidine, and lysine in the diets gave rise to only slight depression of the immune responses. These diets had previously been shown to produce a proportional decrease in both tumor growth and host body weight. Moderate leucine restriction resulted in a paradoxical depression of cytotoxic cell-mediated immunity with little effect on serum blocking activity. Slight increases had previously been noted in the weight of tumors in mice fed leucine-restricted diets. Deficiency or imbalance of essential amino acids in the diet may produce profound depression of immune responses and apparent, marked changes in the immune resistance of the host animal to tumors.

The effect of tryptophan load and vitamin B 6 supplementation on urinary excretion of tryptophan metabolites in human male subjects

1. Urinary excretion of tryptophan metabolites of the kynurenine pathway before and after a loading dose of 2 g of l-tryptophan (both before and during supplementation with vitamin B6) was studied in normal young male subjects and in elderly male subjects with prostatic diseases.

2. The increase in urinary excretion of tryptophan metabolites in the normal male subjects after a loading dose of 2 g of l-tryptophan was unchanged after vitamin B6 supplementation, indicating that this dose does not exceed the normal capacity of the kynurenine pathway.

3. It is therefore concluded that a loading dose of 2 g of l-tryptophan is preferable when studying the capacity of the kynurenine pathway.

4. In about three-quarters of the elderly male subjects with prostatic diseases, the capacity of the kynurenine pathway was normal.

5. In about one-quarter of the subjects with prostatic diseases after a loading dose of 2 g of l-tryptophan there was abnormally high urinary excretion of one or several tryptophan metabolites, which could be normalized by vitamin B6, indicating that the capacity of the kynurenine pathway had been exceeded in these subjects.

6. Urinary excretion of individual tryptophan metabolites after a loading dose of 2 g of l-tryptophan was constant in the same subject when studied under unchanged conditions, whether there was a normal or a decreased capacity of the kynurenine pathway.

7. It is concluded that a single determination of urinary excretion of tryptophan metabolites after a loading dose of 2 g of l-tryptophan is sufficient to determine the capacity of the kynurenine pathway.

The prematurely evoked synthesis of liver tryptophan oxygenase

Livers of normal rats are devoid of catalytically or immunochemically reactive tryptophan oxygenase (EC 1.13.1.12) up to the 10th postnatal day; the enzyme reaches adult concentrations on about the twentieth day. Premature tryptophan oxygenase synthesis can be evoked in 4-day-old rats: if an injection of glucocorticoid is followed, a day later, by an injection of tryptophan, adult levels of tryptophan oxygenase activity and antigen content can be attained within 5 hr. The prematurely evoked tryptophan oxygenase is degraded in about 2 days, but the preparatory action of the glucocorticoid is longlasting. Even 4 days later, an injection of tryptophan can evoke significant enzyme formation. Actinomycin D, injected together with or 12 hr before the tryptophan, is not inhibitory, but if injected with the glucocorticoid it prevents enzyme formation upon later injection of tryptophan. The observations suggest that appearance of the new enzyme in developing tissue results from the sequential action of more than one stimulus and that the potentiality for its transcription may develop long before its actual synthesis.