Antibodies to an NH₂ terminal fragment of β(s) globin. II. Specificity and isolation of antibodies for the sickle mutation

The immunochemical specificity of an antiserum produced to an NH₂ terminal 55 residue polypeptide fragment of the β(s) globin, β(s)(1-55), was analyzed with a radioimmunoassay using the radioiodinated fragment as a tracer. These studies show that most of the antibodies have comparable reactivity with β(s)(1-55), β(A)(1-55), β(s) globin, α(A) globin, HbS, and HbA. However, the antiserum contains some antibodies which react only with the species derived from HbS. These 'S' specific antibodies were isolated by absorption of the serum on a column of β(A)(1-55) coupled covalently to Sepharose. The S specific antibodies have markedly diminished reaction with β(A)(1-55) and HbA. The S specificity was localized to the valine substitution at position 6 of the β globin, as shown by inhibition of the binding of the radiolabeled fragment to S specific antibodies by the synthetic peptide β(s)(1-13). These antibodies, which appear monospecific, can be used to study the conformation of the NH₂ terminal region of the β chain of HbS.