Antisera against epitopes resistant to denaturation on T3 (CD3) antigen can detect reactive and neoplastic T cells in paraffin embedded tissue biopsy specimens.

Polyclonal rat antisera, raised against affinity purified CD3 antigen, gave strong immunoenzymatic labelling of T cells in routine paraffin embedded sections, with negligible background staining. The specificity of these reactions was confirmed by staining biopsy specimens from 21 previously phenotyped non-Hodgkin's lymphomas (including 14 of T cell origin and six of B cell origin). It is suggested that the ability of the polyclonal anti-CD3 antisera to detect T cells in paraffin sections is due to the presence in these sera of antibodies against fixation resistant epitopes on CD3 antigen, and that immunisation with purified denatured preparations of other white cell associated antigens may broaden the range of antibodies suitable for the phenotypic analysis of leucocytes in routine histological samples.