A process is disclosed which enables the establishing of comprehensive immunoglobulin-specific reaction profiles of subjects with disorders of the immune function by the individual V gene repertoire of Ig-expressing B cells. The process comprises the isolation of B cells from body fluids, the isolation of individual B cells and their genetic material, the amplification of nucleic acids coding the variable regions of an antibody expressed by a B cell, the recombinant preparation of antibodies by expressing the amplificates, and the determination of the binding capability of the recombinant antibody to antigens.