Diaminobenzidine cytochemistry in cryo-ultramicrotomy for the detection of peroxidases.

Rat erythrocytes and lymphoid cells were fixed by glutaraldehyde and encapsulated in bovine serum albumin plus rabbit IgG globulins for cryo-ultramicrotomy. A technical procedure is described by which endogenous peroxidases of erythrocytes in ultrathin frozen sections were detected by hydrogen peroxide and diaminobenzidine as hydrogen donor. Modifications of this classical cytochemical procedure proved also useful in cryoultramicrotomy for immunoperoxidase labeling of antigenic determinants in rabbit IgG globulins which have been crosslinked within the supporting matrix of cells.