The estimation of the individual human serum proteins by an immunological method.

Now that something is beginning to be known about the functions of the individual serum proteins there is need of a simple and satisfactory way of estimating their concentrations in normal and pathological conditions. It is difficult to do this by physico-chemical methods since serum is a mixture of so many different components. Methods such as electrophoresis distinguish about five main groups, while a more delicate method like the "immunoelectrophoresis" of Grabar and Williams (1953) can demonstrate numerous further components both in the aand /3-globulin groups. Complete purification of one such component by ordinary chemical means is hardly possible for routine estimation, but advantage can be taken either of chemical groupings which may be sufficiently specific to be estimated individually, for example, porphyrin or copper, or of the immunological specificity of antibodies, as in the Grabar-Williams method mentioned above. Antibodies are of course extremely precise in their discrimination, but it is hard to make immunological estimations both quantitative and simple. Measurement by the micro-Kjeldahl technique of precipitated antibody-nitrogen is extremely sensitive and accurate when properly carried out, but the antigen must be genuinely pure, and the method is slow and laborious. New gel-diffusion methods discussed by Augustin (1955) show promise, but are all somewhat difficult for routine use and, moreover, demand initially a fairly precise idea of the protein concentration to be measured. By the simplified serological methods described in this paper it is possible to decide within 24 hours whether the concentration of a given protein in the serum under test is within normal limits, and, if it is deficient, to give an estimate of its concentration to within about 25% each way. The only difficulty of this type of estimation is that of producing the antiserum in the first place, since it is desirable to use a purified or semi-purified preparation for immunization. Although antisera produced by immunization with even apparently pure preparations of proteins nearly always show the presence of antibodies against contaminants, it is nevertheless usually possible when one of the gel-diffusion methods is used, by which a given " line " can be correlated with the presence of a particular protein, to demonstrate with certainty a single antibody component reacting with the protein under investigation.