title: Murine typhus toxin: studies on identification of the neutralizing factor present in normal human serum.
abstract: Studies were made on the isolation and identification of the Rickettsia typhi toxin-neutralizing factor (TNF) previously demonstrated in normal human serum. By means of various methods of separating serum proteins, such as filtration on Sephadex G-200, dextran precipitation, hydroxyapatite chromatography, and ultracentrifugation, TNF was found to be closely associated with purified serum beta-lipoprotein, although no serological relationship with this protein was demonstrated. Lipase as well as trypsin digestion of purified preparations of beta-lipoprotein destroyed the TN activity. No evidence was obtained for an association of TNF with the immunoglobulins or with any serum protein other than beta-lipoprotein. Further studies revealed that (i) serum specimens with TN titers of 1:1024 and others with titers of 1:8 or less contained the same concentration of beta-lipoprotein; (ii) purified preparations of beta-lipoprotein isolated from TNF positive and negative sera, and which had the same protein concentration, differed as much as 250-fold in TN titer; and (iii) the TN activity of a serum could be removed by absorption with antiserum to beta-lipoprotein from a positive donor, but not with antiserum to beta-lipoprotein from a negative donor.
mesh_terms: D000372:Agglutination Tests; D000818:Animals; D000992:Antitoxins / Q000302:isolation & purification*; D002845:Chromatography; D002850:Chromatography, Gel; D003168:Complement Fixation Tests; D006801:Humans; D006882:Hydroxyapatites; D007106:Immune Sera; D005779:Immunodiffusion; D007074:Immunoglobulin G / Q000032:analysis; D007075:Immunoglobulin M / Q000032:analysis; D008049:Lipase; D008074:Lipoproteins / Q000302:isolation & purification; D051379:Mice; D009500:Neutralization Tests; D011817:Rabbits / Q000276:immunology; D012286:Rickettsia typhi / Q000276:immunology; D014357:Trypsin; D014437:Typhus, Endemic Flea-Borne / Q000276:immunology*; D014461:Ultracentrifugation
chemical_list: D000992:Antitoxins; D006882:Hydroxyapatites; D007106:Immune Sera; D007074:Immunoglobulin G; D007075:Immunoglobulin M; D008074:Lipoproteins; D008049:Lipase; D014357:Trypsin