The injection of killed typhoid microbes agglutinated by a specific serum was followed by rapid production of immune antisera. The serum of rabbits injected with these mixtures prevents a lethal condition induced in mice by intraperitoneal injection of living microbes in much smaller doses than serum obtained with untreated microbes.

On the other hand, the injection of the same killed typhoid microbes, mixed together with a flocculate obtained, for instance, from egg protein, and an antiegg precipitant—guinea pig serum—produces a much less rapid appearance of antityphoid immune antibodies than injection of microbes alone.

Another form of lipido proteic complex, utilized as agent with the aim to induce not a lipido proteic response but a higher one in the defense process, was that of allergic precipitates. Through a blender, we obtained from rat and mouse tumors homogenates in which it was no longer possible to see cells. After centrifugation the supernatant fluid was separated, and used as antigen. Part of it was inoculated to guinea pigs, twice at 3-day intervals. The amount of appearing precipitines was determined periodically and the animal bled when the serum had a sufficiently high titre. Using the same antigen and the obtained sera properly diluted, flocculates were obtained. The precipitate separated was injected to animals having the tumor grafted. In a high proportion of cases—in more than 70% in some experiments—the tumors started to show changes 24 hours following the injection of the precipitate, to ulcerate or disappear in the subsequent days. Similar research, using pooled human tumors, is in progress.

Intermediary Lysates And Antigens

Of interest was a special use of the intermediary lysates in order to obtain changes in the antigens, which would facilitate the defense mechanism. Microbes, tissues or other products, serving as antigens were injected, mixed with intermediary lysates from blood or other sources. This was seen to result in a more specific second day defense response. Mice injected with such a mixture of blood intermediary acid fraction plus killed microbes showed resistance to the inoculation, 24 hours later, of the same living microbes in doses otherwise lethal. The protection obtained has a marked degree of specificity.

In experiments now in course, we utilize blended tumors mixed with the intermediary acid lysate fraction, to induce a defense in animals having the same tumor grafted.

The discussion above concerns what could be called the immunological part of the defense reaction. It has to be coupled with many other processes or phenomena which can be systematized as endocrine, vegetative, central nervous or even psychological responses. Some of them could be indirectly related to the intervention of lipids, and possibly involved through them in the immunological responses.

This concept of immunological defense, even under its incomplete aspect has helped us to understand a number of important pathogenic problems, including two which have been of particular interest to us: infectious disease and cancer. Our study of the infectious diseases under this aspect was reported in a preliminary communication in 1919. (37) In 1942, this part of the research was presented at the Congress of Medicine in Mexico and published in the journal "Pasteur." (38)