Method for detection of antibody against low molecular weight antigen (hapten)--production and detection of antibody against histamine H2 receptor of antibody against histamine H2 receptor antagonist "Famotidine".

Antibodies against histamine H2-receptor antagonist "Famotidine (FAMO)", molecular weight 337, chemical name; N-sulfamoyl-3-(2-guanidinothiazol-4-ylmethylthio) propionamide, were produced by subcutaneously injecting rabbits with an albumin and FAMO conjugate covalently bound with 1-ethyl-3-(3-dimethyl-amino-propyl) carbodiimide (ECDI). Two new detection systems for antibody titration were developed and employed. In one method, the antigen FAMO was tagged to sheep red blood cells (SRBC) and analysed qualitatively by a fluorescence activated cell sorter (FACS) using a second fluorescence isothiocyanate (FITC) labeled antibody. In the other method, CH-Sepharose beads were employed in place of SRBC and Horse Radish Peroxidase (HRP) was labeled to the second antibody instead of FITC used in the former method. HRP of the immune complex was colorimetrically measured with DAB-H2O2 to analyse the fine antibody titer. These high sensitive detection methods revealed the existence of IgG type of FAMO antibody. The detection sensitive detection methods revealed the existence of IgG type of FAMO antibody. The detection sensitivity was approximately 50 to 100 times higher in the later method with HRP than in the former. Furthermore these two methods could be deemed to be a good model system for a receptor assay.