Modifications to the standard techniques of somatic cell fusion are presented which have resulted in the derivation of hybrid cell lines secreting monoclonal antibody to the low molecular weight antigen ferredoxin. Antibody secreted by one of these lines has been purified using the technique of protein. A sepharose chromatography. Using standard immunochemical methods it has been determined that this monoclonal antibody has an approximate isoelectric pH of 8.5 - 8.6 and belongs to the IgG₂[sub b] subclass of immunoglobulin. / Science, Faculty of / Microbiology and Immunology, Department of / Graduate

It was established that antibodies could be evoked in rabbits against ferredoxin purified from cultures of Clostridium pasteurianum and against its performic acid oxidized derivative. The extent of cross-reaction was studied between the two antisera and four related antigens: native ferredoxin, iron-sulfide free ferredoxin, performic acid oxidized ferredoxin, arid S-carboxymethylated ferredoxin. All combinations demonstrated cross reactivity by complement fixation, and in the case of oxidized ferredoxin antiserum, three preparations, native ferredoxin, iron sulfide free ferredoxin, and performic acid oxidized ferredoxin precipitated antibody. The data obtained with these cross-reactivity studies Indicated that the cysteine-containing regions of the ferredoxin molecule were not critically involved as antigenic determinants. The C-terminal region of the protein was considered for further study. This octapeptide was synthesized and tested for its ability to combine with antibody directed against both native ferredoxin and its performic acid oxidized derivative. The peptide exhibited specific binding to both antisera as demonstrated by inhibition of complement fixation and precipitation, and by equilibrium dialysis experiments. It is suggested that C. pasteurianum ferredoxin is antigenic in rabbits, that cysteine residues are not involved in at least two of the antigenic regions of the protein, and that the C-terminal octapeptide is one of the antigenic determinants of this molecule. / Science, Faculty of / Microbiology and Immunology, Department of / Graduate