An immunochemical study of the proteins in cerebrospinal fluid.

Cerebrospinal fluid was obtained by lumbar puncture. Only fluids containing fewer than 100 red blood cells/ c.mm. were studied. The cerebrospinal fluid protein was concentrated by the technique of Grant (1957), in most cases to between 500 and 1,000 mg./100 ml. Cerebrospinal fluids with protein concentrations already in this range were not further concentrated. The details of the immunochemical gel diffusion precipitin technique used are described by Soothill (1962). It is an adaptation of the method of Gell (1957). Proteins studied were albumin, siderophilin, y globulin, high molecular weight a2 glycoprotein, ,B lipoprotein (arranged in order of molecular weight in Table I), and, in a few instances, caeruloplasmin and a component of complement. The method entails visual matching of patterns of precipitate produced by suitable dilutions of cerebrospinal fluid and of serum, when they react with a standard series of dilutions of specific antiserum. Direct readings of the concentration ratios are obtained (after multiplication by the concentration factor). The error of the method, which entails a constant coefficient of variation for each protein over a wide range of concentrations, has been described in detail by Soothill (1962). It varies with different proteins, but the coefficient of variation of the estimation is about 18% (see Table 1). Reactions of identity were demonstrated by the technique of Ouchterlony (1948). Immunoelectrophoresis was performed by a modification of the technique of Grabar and Williams (1953). A rabbit was immunized to cerebrospinal fluid protein, concentrated to 1 g./100 ml., using a Freund's adjuvant preparation subcutaneously and a saline solution intravenously, by the immunization course described by Soothill (1962). The antiserum (six volumes) was absorbed with one volume of human serum, with incubation at 37°C. for two hours and at 4°C. for 16 hours, after which the precipitate was removed by centrifugation.