Immunoglobulin profiles of the chronic antibody response: discussion in relation to brucellosis infections.

The use of a sensitive and quantitative radioimmunoassay has enabled much finer dissection of the immunoglobulin-antibody profiles for an individual immune response. The kinetics of the response are considered in relation to the switch from IgM to IgG antibody production. In the domestic fowl, the kinetics of this switch varied with different antigens: whereas the response to a thymus-dependent antigen proceeded through a brief 19S response to a declining 7S response, the response to a thymus-independent antigen failed to switch from 19S to 7S for several weeks and consisted of repeated excursions of 19S antibodies. When injected intravenously and simultaneously, Salmonella adelaide 0 (killed) organisms (thymusindependent) and sheep red cells (thymus-dependent) interact so that the response to the latter fails to switch from 19S to 7S and consists of repeated excursions of 19S antibody. The changed character of the sheep red cell response is interpreted as being due to lack of 7S antibody. Passive antibody to either sheep red cells or to S. adelaide produced an inhibition of the sheep red rell response so that only one excursion of 19S antibody was observed. The use of the radio-immunoassay enables an independent measurement of all IgM, IgG and IgA antibody to the surface antigen of Brucella obortus. The test, when applied to forty-six sera from individuals with various types of brucellosis, successfully detected antibody in many instances in which conventional serological tests were negative, and such antibody (if IgM) was associated with acute or (if IgG or IgA) with chronic cases of brucellosis. The radioassay test should prove highly valuable effectively to eliminate, in individual patients, the diagnosis of brucellosis based on the inability of conventional tests to detect significant antibody levels.