Biomedical subjects

P Medawar

Publications and source records attributed to P Medawar.

At least 19 recordsLinked to original sources

PubMed1984

A diet enriched in vitamin A acetate or in vivo administration of interleukin-2 can counteract a tolerogenic stimulus.

A conventional diet enriched in retinyl acetate (vitamin A acetate; VAA) or in vivo administration of exogenous interleukin-2 (IL-2) can effectively annul the otherwise tolerogenic stimulus represented by (CBA X C57BL/10ScSn) F1 cells injected intraperitoneally into newborn CBA mice. On the basis of these data and results of others, we postulate that an antigenic stimulus associated with a relative lack of IL-2 (or generally the lack of a 'secondary stimulus') can be tolerogenic rather than immunogenic. However, the tolerogenicity of the antigenic stimulus can be substantially reduced or even converted to sensitization (R. P. Cleveland & H. N. Claman, J. Immun. 124, 474-480, 1980), when the antigenic signal is appropriately associated with a concomitant or additional stimulus possibly mediated through IL-2.

Animals↗

PubMed1979

An influence of diet on transplantation immunity.

It was discovered by chance that mice raised under otherwise entirely conventional conditions of husbandry but fed upon autoclaved diet (diet A) had stronger cell-mediated immune reactions than those of mice raised under the same conditions but with an unmodified diet (diet B) : skin allografts were rejected more quickly, transplantation tolerance was more difficult to procure and fibrosarcomas induced by the injection of methylcholanthrene (MCA) arose more slowly and less often. Analysis showed that these findings could be explained at least in part by the discovery of Mertin & Hunt (1976, p. 928) that a partial deprivation of polyinsaturated fatty acids led to an intensification of cell-mediated immunity; on the other hand, experiments with dietary mixtures made it seem unlikely that this was the whole explanation and pointed towards some positive immunopotentiation by an ingredient of autoclaved diet. This, it was proposed, might be a compound of unknown composition resulting from the interaction of vitamin A with other dietary constituents. This interpretation was not supported by direct evidence but by confirming that retinol derivatives, especially retinyl acetate, could exercise an immunopotentiation of the kind and degree under investigation: retinyl acetate could counteract the immunosuppressive action of linoleic acid, though retinyl methyl ether was ineffective. Although retinyl derivatives may protect against MCA tumours by impeding its metabolic conversion to an oncogenic form, the effects of an autoclaved diet upon skin allograft survival, the induction of tolerance and the formation of tumours is probably mediated through an immunological mechanism.

Animals↗

PubMed1977

Adipose tissue: contributions of nature and nurture to the obesity of an obese mutant mouse (ob/ob).

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Adipose Tissue↗

PubMed1977

Anaplasia rediviva.

Anaplasia refers to the apparent retrogression toward an embryonic state that occurs in some human and animal tumors, the consequence, presumably, of a derepression of genes that would normally have been switched off in the course of development. The fetal substances newly formed in tumors are identified immunologically and are therefore referred to as "antigens." Some such antigens, for example, carcinoembryonic antigen and alpha-fetoprotein, and blood-group precursor substances have great promise diagnostically but play no known part in resistance to malignant growth. The reawakened fetal antigens that are of special interest and importance are those that are capable of arousing cell-mediated immunity and thus may contribute to antitumor immunity. Modern research, therefore, rehabilitates an etiologc notion earlier thought to have been discredited.

Anaplasia↗

PubMed1976

The significance of embryonic reexpression in cancer.

Irradiated syngeneic mouse testicular cells and the first-trimester human fetal tissue cells protect mice partially against tumors induced by methylcholanthrene or against a syngeneic transplantable mouse tumor, Meth A, respectively. For future research it is suggested that experiments should have a therapeutic rather than a prophylactic design and that the induction of tolerance to fetal antigens could be a highly informative procedure.

Animals↗

PubMed1975