The presence in serum of proteins which are immunologically cross-reactive with Tamm-Horsfall glycoprotein.

Affinity chromatography, with rabbit anti-(human Tamm-Horsfall glycoprotein) IgG, was applied to the isolation from normal human serum of protein, which is immunologically cross-reactive with the urinary glycoprotein. The antigen-antibody complex was dissociated with the use of sodium thiocyanate solution, a medium which fails to dissociate urinary Tamm-Horsfall glycoprotein-antigen complex. The cross-reactive serum proteins were isolated in amounts of 19-24 mg/l of serum. They have apparent molecular weights, assessed by disc-gel electrophoresis in the presence of sodium dodecyl sulphate, of 125 000, 84 000 and 74 000 respectively, with mobilities differing from that of urinary Tamm-Horsfall glycoprotein. They have a much lower immunoreactivity towards the antibody than does the urinary glycoprotein. Tamm-Horsfall glycoprotein could not be demonstrated in normal serum by the techniques used. The implications of these findings are discussed in terms of pathology involving Tamm-Horsfall glycoprotein.