Characterisation of monoclonal antibodies to adrenocorticotrophin.

We have produced 8 monoclonal antibodies to adrenocorticotrophin (ACTH) derived from immunisation with ACTH (1-24) conjugated to bovine serum albumin or ACTH (1-39) linked to chicken immunoglobulin by a novel method. Antibody specificity was assessed by studying the binding of purified human ACTH, synthetic ACTH (1-24), fragments of ACTH and peptides from the ACTH precursor molecule which have sequence homology. A wide range of specificities was demonstrated. Thus antibody 3H9 recognises the extreme N-terminal sequence (ACTH 4-10), antibody 1A12 is specific for residues 10-18 including alpha MSH, antibody 1D1 is specific for the mid N-terminal sequence but not alpha MSH, and antibody 2A3 is specific for the C-terminal portion (ACTH 18-39). These monoclonal antibodies can be easily purified and labelled and their defined specificities make it possible to select antibody combinations which provide the basis for 2-site immunometric assays for ACTH.