Abstract
Formalin fixation followed by routine paraffin embedding allows the demonstration of intracellular immunoglobulin by a sandwich technique using either peroxidase or fluorescein isothyocyanate labelled antibody conjugates. The results compared favourably with those obtained using either the fresh frozen or the Sainte-Marie method for preserving tissue immunoglobulins. The formalin-paraffin method with peroxidase-labelled antibody has advantages for routine use. Morphology is excellent, preparations are permanent, and retrospective studies of stored paraffin-embedded tissue are possible. Some of the problems of labelled antibody studies are discussed.