Immunological Demonstration of a Substance in Rat Blood Associated with Tissue Growth

IT was shown in an earlier paper (Darcy, 1955) that it is possible to distinguish the blood plasma of tumour-bearing rats from that of control rats by means of the gel-diffusion technique of Ouchterlony (1948). This technique is essentially the precipitin reaction carried out in a gel. A strong precipitating antiserum is prepared against the antigen, in this case rat plasma (a mixture of antigens), and the two reactants are allowed to diffuse towards one another through an agar gel. Precipitation of the antigen-antibody complexes occurs in the form of bands or lines, each of these representing one or more antigenic components of the original antigen mixture. Ouchterlony's method permits two such antigen mixtures to be compared in such a way that it is possible to tell at a glance whether there is a component in one which is absent from the other or whether a particular component is in substantially higher concentration in one than in the other. The earlier study revealed several differences between the plasma of tumour-bearing rats and their controls, the most striking being: (1) The leading band of the normal plasma, i.e. the band that migrated in front of the others towards the antiserum, was considerably weaker in the cancer than in the normal blood. This band has since been found to be produced by serum albumin. (2) In the cancer plasma this albumin band was preceded by a group of faint lines (designated as "K" lines) which were not evident in the precipitin spectrum of the normal plasma. Their presence appears to be due partly to the receded position of the albumin band which thus "uncovers" them, and partly to higher concentration or higher speed of diffusion of the antigens they represent. (3) A line present in the cancer plasma spectrum which was absent from the normal. The substance which this line represents could be made to appear artificially in the plasma of normal rats by bandaging them tightly around the abdomen and not fasting them before bleeding. (4) Certain of the other antigens in the cancer plasma appeared to be in considerably lower concentration than in the normal, but some were higher. The above characteristics were observed in the plasma of rats with well-established tumours. They were not seen in animals bearing the Walker tumour until about 6 days after its transplantation. A preliminary study (Darcy, unpublished) has since been made of human …