A simple method for isolating specific antibodies to complement components.

A simple procedure for isolating specific antibodies to complement components C3, C4 and C5b-9 from whole rabbit antisera or immunoglobin preparations is described. Antisera are first reacted with complement-treated sheep erythrocyte membranes. Immunoglobulins are eluted from the washed membranes with acetic acid at pH 2.4, and further purified by one absorption/desorption step on Protein A Sepharose. The final protein preparations contain greater than 90% rabbit immunoglobins, as assessed by quantitative immunoelectrophoresis and SDS polyacrylamide gel electrophoresis. Binding assays with radioiodinated protein preparations indicate a content of specific antibodies in the range 5-55% of total protein. Since there is virtually no non-specific binding of protein to control cells or membranes, the immunoglobulin preparations are well suited for use in sensitive immunoassays for complement components.