Some relations between hydrogenion concentration and antigenic properties of proteins. 1

The recent work of J. Loeb 2 and others has indicated the important rôle which the hydrogen-ion concentration plays in affecting the physical and chemical properties of proteins. Our studies were designed to determine whether certain biological properties of the proteins were also affected by hydrogen and hydroxyl-ions over the range of concentration which markedly affects such properties as osmotic pressure, swelling power, viscosity, power to combine with ions, electrical charge, etc.

Our first studies upon the anaphylactogenic properties of proteins were made with gelatin. We failed to produce anaphylaxis in guinea pigs with this protein when it was introduced intravenously or intraperitoneally in solutions at its isoelectric point (P_H = 4.7) and in more acid and in more alkaline solutions. With pure, crystallized hen ovalbumin (isoelectric point, P_H = 4.8) we obtained anaphylaxis in the guinea pig readily and consistently. When this protein is introduced into the animal in solutions more acid than those in which it is isoelectric, it is a distinctly more potent antigen than when introduced in the solution with which it is isoelectric or in more alkaline solutions. Sensitization with 5 and intoxication with 50 milligrams of ovalbumin gives acute and usually fatal anaphylaxis when the sensitization is obtained with the protein at P_H 2.0-2.5 regardless of the acidity of the intoxication dose. Sensitization with the same dose of the protein at P_H 4.7-4.8 or at 9.0-10.0, regardless of the form of the intoxicating dose, gives reactions which range from only barely perceptible anaphylaxis to shock which is evidenced by the usual paralysis but which is usually lacking in the respiratory syndrome, the “air hunger,” and which is practically never fatal. With larger sensitizing doses of protein (50 milligrams) acute anaphylaxis (including the respiratory as well as the paralytic reaction) can be produced by the protein at any of the three hydrogen-ion concentrations studied.